Development of Sulfonic‐Acid‐Functionalized Mesoporous Materials: Synthesis and Catalytic Applications

Author Manuscript

Title: Development in Sulfonic Acid-Functionalized Mesoporous Materials: Synthesis and Catalytic Applications

Authors: Esmail Doustkhah, Ph.D; Jianjian Lin; Sadegh Rostamnia, Ph.D; Christo- phe Len, Ph.D; Rafael Luque, PhD; Xiliang Luo; Yoshio Bando, PhD; Kevin C.-W. Wu, Ph.D; Jeonghun Kim, PhD; Yusuke Yamauchi; Yusuke Ide, Ph.D

This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofrea- ding process, which may lead to differences between this version and the Version of Record.

To be cited as: 10.1002/chem.201802183

Link to VoR: https://doi.org/10.1002/chem.201802183 Development in Sulfonic Acid-Functionalized Mesoporous Materials: Synthesis and Catalytic Applications

Esmail Doustkhah,1 Jianjian Lin,2 Sadegh Rostamnia,3* Christophe Len,4 Rafael Luque,4,5* Xiliang Luo,2 Yoshio Bando,1,6 Kevin C.-W. Wu,7 Jeonghun Kim,8 Yusuke Yamauchi2,8,9* and Yusuke Ide1*

1 International Center for Materials Nanoarchitechtonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan 2 College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, China 3 Organic and Nano Group (ONG), Department of Chemistry, Faculty of Science, University of Maragheh, P.O. Box. 55181-83111, Maragheh, Iran 4 Sorbonne Universités, Université de Technologie de Compiègne (UTC), EA 4297 UTC-ESCOM, CS 60319, 60203 Compiègne Cedex, France 5 Departamento de Quimica Organica, Universidad de Cordoba, Edif. Marie Curie, Ctra Nnal IV-A, Km 396, 14014 Cordoba, Spain 6 Australian Institute for Innovative Materials (AIIM), University of Wollongong, Squires Way, North Wollongong, NSW 2500, Australia 7 Department of Chemical Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan 8 School of Chemical Engineering and Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, Brisbane, QLD 4072, Australia 9 Department of Plant & Environmental New Resources, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 446-701, South Korea

Keywords: mesoporous materials; catalysts; sulfonic acid functionalization

Sulfonic acid-based mesostructures (SAMs) have been developed in recent years and have important catalytic applications. The primary applications of these materials are in various organic synthesis reactions such as multicomponent reactions, carbon-carbon bond couplings, protection reactions, and Fries and

Beckman rearrangements. This review aims to provide an overview of the recent developments in the field of SAMs with a particular emphasis on the reaction scope and advantages of heterogeneous solid acid catalysts.

Content Abstract 1. Introduction 2. Precursors for sulfonation 3. Development of new mesostructures for the fabrication of sulfonic acid-based mesostructures (SAMs)

3.1. Carbon mesoporous sulfonic acids (CM-n-SO3H)

3.2. Sulfonated ordered mesoporous polymers (OMP-SO3H) 3.3. Sulfonated mesoporous composites 3.3.1. Sulfonated polymer-silica (SPS) mesocomposites 3.3.2. Sulfonated carbon-silica (SCS) mesocomposites

3.4. Sulfonated periodic mesoporous organosilicas (PMO-SO3H) 4. Conclusions 5. Abbreviations 6. References

In recent years, demands for the design and fabrication of new mesoporous catalysts with superior features such as being recyclable, having a unique molecular architectures and being atom economical to adhere to

[1] the tenants of green chemistry are increasing. Heterogeneous solid acid catalysts play an important role in the development of greener catalytic protocols due to their recoverability, reusability and stability in chemical processes. Among these catalysts, sulfonic acid-based mesostructures (SAMs) are a class of hybrid organic-inorganic nanoporous materials that are attracting increasing attention from researchers due to their aforementioned advantages.[2] Sulfonic acid-functionalized mesoporous materials are superior to other corresponding solid acid catalysts because they can provide a large number of reaction sites and realize the size selectivity.[3] In addition, these materials can be co-functionalized with other functional groups to increase their efficiency by balancing their hydrophobicity, acidity, and basicity.[4]

Our ongoing research focus is the development of catalytic applications of mesoporous materials.[5]

This contribution seeks to review the recent advancements in the catalytic applications of SAMs with diverse structures including silicates, polymers, hybrid polymer-silicates, organosilicates, and carbon- containing compounds in a comprehensive manner (Scheme 1).

The preliminary reports on SAMs in 1998 were based on silica frameworks.[6] The earliest versions of

SAMs were prepared by two general routes: 1) post-functionalization of mesoporous silica with 3- mercaptopropyltrimethoxysilane (MPTMS) and 2) cocondensation of MPTMS and a silica source (e.g., tetraethylorthosilicate (TEOS) and tetramethylorthosilicate (TMOS)). The final key step in the production of

SAMs was the oxidation of the thiol groups to sulfonic acids using oxidants such as H2O2. In this regard, many advances,[6-7] including enhancing the MPTMS loading capacity using a coating method,[6c] using cocondensation with TMOS instead of TEOS,[6a] replacing calcination with extraction,[7g] and cofunctionalizing MPTMS with octyl substituents to enhance the catalytic activity by increasing the acidic strength and hydrophobicity,[8] have been made. Importantly, a number of the prepared SAMs are primarily employed in biomass conversion.[6, 7g, 9] In 2006, Melero and coworkers[10] extensively reviewed and discussed all types of sulfonating precursors and their catalytic applications. However, their review was

This article is protected by copyright. All rights reserved limited to the SASMs that had been reported to that date. Herein, recent advances in all areas of sulfonic acid-based mesoporous materials will be discussed in detail.

Catalyzing the synthesis of 2,2-bis(5-methylfuryl)propane via the condensation of acetone with 2- methylfuran,[6b] the esterification of D-sorbitol with lauric acid,[11] the synthesis monolaurin through the direct esterification of glycerol with lauric acid,[9] the three-component syntheses of 3,4- dihydropyrimidinones through Biginelli reactions,[12] Fries and Beckmann rearrangements,[13] the syntheses of polyhydroquinoline derivatives,[5c] the synthesis of β-amino carbonyls via Mannich reactions,[14] the synthesis of xanthenes and bis(indolyl)methanes,[15] syntheses of benzoxazole derivatives,[16] the synthesis of 4-phenyl-1,3-dioxane,[17] the synthesis of chromenes from chromanols,[18] the esterification of salicylic acid with dimethyl carbonate,[19] the multicomponent synthesis of spiro[indole-tetrahydropyrano(2,3- d)pyrimidine] derivatives,[20] etc.[21] illustrate the versatility of these materials in catalytic applications.

Scheme 1. Overall strategies for the sulfonation of mesoporous materials.

Several sulfonic acid precursors (SAPs) have been reported for the sulfonation of mesoporous materials.

Sulfonation with concentrated sulfuric acid is the most common method. Among the organosiloxane-based

SAPs, MPTMS is generally employed to link silica with siloxane moieties. However, these methods are less than ideal and can not necessarily be used in the sulfonation of all types of mesoporous compounds.

Consequently, several types of SAPs have been developed to modify mesoporous materials to control their acidity, leaching, hydrophobicity and other parameters. For example, increases in hydrophobicity, and the concomitant improvements in catalyst deactivation by water and the mass transfer of hydrophobic compounds, could be achieved in a facile manner by replacing the propylsulfonic acid moiety in MPTMS with phenylsulfonic acid. Some of the most commonly used SAPs for the sulfonation of mesoporous materials are summarized in Table 1.

Recently, supported N-propylsulfamic acids have attracted significant attention in the field of catalysis.[22] Sulfamic acid-based catalysts can be regarded as strong acids that are zwitterionic in the absence of water.[23] Moreover, such catalysts are easily separable from reaction mixtures and can be recycled a number of times when supported on the surface of mesopores. In neutral or alkaline solutions, sulfamic acid derivatives can be boiled without appreciable hydrolysis; however, they slowly hydrolyze under aqueous conditions.[23a] Hajjami and coworkers[22d] prepared MCM-41-N-propylsulfamic acid in a one-pot multicomponent synthesis from 1-amidoalkyl-2-naphthols and studied its catalytic activity.

The functionalization of fluoro-based sulfonic acid precursors (F-SAP) inside the mesopores was first reported by Harmer and coworkers.[24] These hybrid mesostructures are strongly acidic due to the presence of electronegative fluorine atoms. However, the preparation and stability of these materials are major drawbacks as they often undergo leaching, which causes deactivation.[25] 1,2,2-Trifluoro-2-hydroxy-1- trifluoromethylethane sulfonic acid sultones, F-SAPs, can be directly anchored to silica surfaces by a direct synthetic strategy.[26] Harmer et al.[24] disclosed another strategy for the preparation of F-SAPs through a platinum-catalyzed hydrosilylation procedure (Scheme 2), and the F-SAP can then be anchored to the silica surface by a cocondensation reaction or grafting.[27]

Scheme 2. Synthesis of F-SAP. [24]

Phenylsulfonic acid siloxane-based precursors (Ph-SAP- Table 1, entries 6, 7, and 11) are advanced types of SAPs that have improved acidic properties relative to the analogous commercial versions such as

[31i] [36] Amberlyst-15. Lindlar et al. reported the synthesis of MCM-41-Ph-SO3H (using Ph-SAP in Table 1, entry 6) with enlarged pore diameters up to 60 Å using swelling agents. The phenyl groups were first grafted onto the silica surface and subsequently sulfonated with chlorosulfonic acid. However, in this step, free silanol groups can also undergo sulfonation. To avoid this phenomenon, they incorporated capping agents

(such as trimethoxymethylsilane) that can be grafted after the functionalization of the phenyl precursor and will protect the free silanols from sulfonation with chlorosulfonic acid. For the sulfonation of mesoporous silica materials, grafting is the most commonly selected method due to its advantages over cocondensation functionalization (in which the structure detection agent (SDA) would need to be removed by extraction).

However, the Launay and Gédéona group found that a low temperature and gentle calcination at 200 °C can completely remove the P123 from the extracted sample. Therefore, the P123 surfactant in SBA-15-Ph-

[31a] SO3H, which is prepared by a cocondensation method, can be removed by calcination.

Entry Structural formula Properties and applications Reference -A famous family of SAPs that are generated 1 [6a, 7d] by the oxidation of MPTMS Et -Prepared in one step prior to functionalization Et O F F F F and attached to a silica surface through the O Si O 2 SO3H siloxane moiety Et O F F F F -Strongly acidic and highly hydrophobic [27] -Expensive to produce -Can be directly functionalized onto a silica surface 3 -Strongly acidic due to the fluorine atoms [26, 28] -Higher leaching and more expensive -Attaches to a silica surface via the siloxane moiety 4 [29] -By adding a nucleophile, a wide variety of

bifunctionalized SAMs can be produced -Can directly attach to a silica surface or undergo ring opening in the presence of an 5 [30] amine

-Can be prepared in two steps: 1) functionalization of PTS onto a silica surface; 6 [25, 31] 2) sulfonation of a phenyl group by H2SO4 -Their acidity is similar to that of commercial sulfonated Amberlyst-15 resins -It can easily hydrolyze to give other SAP and O Cl S can be used to tailor surfaces through O 7 R O nucleophile attack of -SO2Cl moieties. These [32] R Si O O R kinds of precursors can decrease the pore size and surface area -Is similar to entry 6’s precursor except with more flexibility and a longer length 8 -These two SALs are more water tolerant than [31j]

the SAL shown in entry 1

-Can be embedded into a silica wall and then [33] 9 oxidize to -SO3H to give a uniform distribution of sulfonyl groups

-Can be prepared from chlorosulfonic acid and ATPS. 10 [22-23] -Converts to a zwitterion in water and slowly hydrolyzes to the amine and H2SO4 -Generally used for CMs and functionalized 11 through displacement of the diazonium[34] in [35]

the presence of H3PO2

(SAMs)

3.1. Carbon mesoporous sulfonic acids (CM-n-SO3H)

Mesoporous carbons (MCs) were developed recently and are synthesized from hard or soft-templating carbonization.[37] Owing to their high stability and potential for undergoing sulfonation, MCs have emerged as the next generation of sulfonic acid-based carbon mesopores (SACMs), and they are stable at high temperatures.[35a, 38] Wu et al.[38a] pioneered a sulfonation of the controllable carbonized CMK-3 via a vapor- phase method in a closed autoclave with fuming H2SO4 and subsequent treatment with pure SO3 gas. This group also studied the influence of carbonization on the functionalization of CMK-3 at various temperatures from 673-1173 K. At 1173 K, a highly ordered mesoporous carbon material could be produced (Scheme 3).

However, the balance between the structural order and the content of polycyclic aromatic carbons deteriorated when the carbonization temperature was 873 K. The presence of polycyclic aromatic rings was found to be essential for obtaining a highly functionalized -SO3H-containing material. According to the

XRD patterns, the intensity of the main diﬀ raction lines slightly decreased when using vapor transfer sulfonation, which indicated that the ordered 2D hexagonal p6mm structure of CMK-3(873)-SO3H was preserved during sulfonation. This material was then tested as a catalyst for the Beckman rearrangement of cyclohexanone oxime and the condensation of bulky aromatic aldehydes.

[38a] Scheme 3. Functionalization of CMK-3 with fumed H2SO4.

Following that study, Janaun and Ellis[39] extensively explored the effects of sulfonation on the structure of MC and its corresponding effects on the catalytic activity of CMK-3-SO3H. They also attempted the sulfonation of the material before and after the removal of the silica template. Their research showed that the sulfonation of CMK-3 after removal of the template can result in remarkable damage to the internal pores, whereas sulfonation before removing the silica template did not impact the mesoscopic structure. The authors attributed these findings to silica serving as a barrier, which prevented sulfuric acid from penetrating into the internal surface. TEM images (Figure 1) indicated that two different structures were obtained from the sulfonation of MC before and after silica removal (after silica removal, sulfonation caused the total destruction of the pore walls). The carbonization temperature was 400 °C, and the proposed system was successfully tested in biodiesel production.

Figure 1. CMK-3-SO3H TEM images of the two different structures obtained from sulfonation of MC before (a) and after (b) removal of the silica template (Reproduced from ref. [39]).

[38b] Later, Sels and Jacobs further optimized the sulfonation of CMK-3-SO3H. Instead of fuming H2SO4 or SO3 gas, concentrated sulfuric acid at a higher temperature was employed in the sulfonation of the carbonized mesoporous carbon inside SBA-15, and then the SBA-15 (hard template) was removed using

HF. Zhang and coworkers[40] hydrolyzed cellulose into glucose with the highest yield to that point using

CMK-3-SO3H at a high temperature. The stability of CMK-3-SO3H at high temperature (250 ºC) was key to achieving the high yields (94% cellulose conversion with a glucose yield of 74.5%).

An alternative approach was also developed for the preparation of sulfonated CMK-5 (CMK-5-

[41] SO3H) with the reduction of the diazonium salts, bearing sulfonic acid functional group, with hypophosphorous acid, and the final material was employed as a catalyst in the production of bisphenols

(Scheme 4). The catalytic performance was compared with those of two other SASMs (e.g., SBA-Pr-SO3H and Et-PMO-SO3H), and the fully sulfonated CMK-5 provided the best results. The catalytic activity of sulfuric acid was also tested, but it showed worse results in terms of yield versus time. However, CMK-5-

SO3H was a greener, more recoverable and more reusable solid acid catalyst than deleterious and corrosive sulfuric acid.

Scheme 4. Sulfonation of CMK-5 with benzene para-diazonium sulfonic acid (Reproduced from ref. [41]).

Another type of sulfonated ordered mesoporous carbon (OMC-SO3H), a member of the SACM family, was also prepared, and various parameters of the preparation procedure were studied. These parameters include the effect of aging temperature on the mesoscopic structure at three different points [(OMC-n-SO3H) n = 100, 130, and 150 ºC], and the synthesis was carried out by nanocasting silica SBA-15 and using furfuryl alcohol as the carbon source.[41b] Aging at 150 ºC afforded materials with a higher pore diameter and therefore a larger pore diameter than the corresponding OMC. As a result, sulfonation decreased the pore diameters of these materials. Compared to SBA-Ph-SO3H, OMC-SO3Hs was more acidic and therefore showed higher catalytic activity. Accordingly, OMC-150-SO3H provided a higher conversion of oleic acid to the corresponding ester with ethanol, and OMC-130-SO3H and OMC-100-SO3H resulted in similar conversions. SBA-Ph-SO3H provided the lowest conversion among the OMC-SO3Hs tested, but interestingly, it was more efficient than commercial Nafion (Figure 2).

Figure 2. Conversion of oleic acid to the ester with ethanol over different catalysts over 10 h (Reproduced from ref. [41b]).

Li and Liang[42] anchored phenylsulfonic acid groups onto the surface of OMC through an in situ radical polymerization of sulfanilic acid and isoamyl nitrite under ambient conditions. By this method, they reduced the number of synthetic steps to one and subsequently utilized OMC-SO3H as a support for palladium nanoparticles via PdCl2 reduction using NaBH4 as the reducing agent. The synthesized nanocatalyst was successfully employed in the electrooxidation of formic acid (cyclic voltammetry and chronoamperometry).

[35b, 43] The catalytic activity of CMK-5-SO3H was also investigated in a range of organic reactions, such as the silylation of alcohols and phenols with hexamethyldisilazane at room temperature in dichloromethane, which was achieved in high yields, and the synthesis of pyrimidine derivatives.[43a] The latter reaction was performed in ethanol at room temperature. The catalyst could be recycled several times with no significant loss in its activity, and excellent yields of the derivatives could be generated in the first runs with short

[43b] reaction times. In a separate work, CMK-5-SO3H was also employed as a catalyst for the solvent-free one-pot synthesis of coumarins through a Pechmann condensation (Scheme 5). Coumarins could be synthesized from phenols and ethyl acetoacetate at moderate to higher temperatures (typically 130 ºC), and

[35b] CMK-5-SO3H was highly stable under the investigated conditions.

[35b, 43] Scheme 5. Synthesis of CMK-5-SO3H and its catalytic applications in organic reactions.

Corma and coworkers[35a] recently designed a new and interesting sulfonic acid-based mesoporous carbide derived from ordered silicon carbide with an extraordinary high specific surface area (up to 2800 m2 g−1). This material was designed via the selective extraction of silicon from ordered mesoporous silicon carbide and subsequent functionalization with sulfonic groups, and it is an excellent solid acid catalyst for the esterification of stearic acid to ethyl stearate (Figure 3).

[35a] Figure 3. Synthesis of SiC-derived MC-SO3H by a hard-templating approach (Reproduced from ref. ).

In addition to the nanocasting method, self-assembly via soft templating was recently developed, and it has surpassed nanocasting and hard templating in the preparation of OMCs (Figure 4). This method was pioneered by Dai et al.,[44] Nishiyama et al.,[45] and Zhao et al.,[46] and it has advantageous over nanocasting due to the reduced preparation costs, the possibility for large scale production, the lower number of synthetic steps, the narrower pore size distribution and the shorter synthesis time.

Figure 4. Synthesis of OMPs with various structures (Reproduced from ref. [46a]).

In this way, OMC-SO3H could be directly prepared by the self-assembly of resorcinol/formaldehyde

(RF) under aqueous conditions using F127 as an SDA.[47] The impact of various factors on the resulting properties of the OMC-SO3H were studied. The obtained organic mesoporous polymer (OMP) was carbonized at high temperature (> 400 °C) under an inert atmosphere to produce OMC. The acid (HCl) concentration and molar ratio of resol and F127 were found to have significant effects on the mesoporous structure during the polymerization process. According to their report, a highly structured OMC could be manufactured when the acid concentration was 0.6-2.0 M and the mass ratio of resol to F127 was 3.5-4.0.

Sulfonation could be achieved using concentrated H2SO4 at moderate temperatures, and the temperature must be carefully controlled as OMCs are susceptible to H2SO4 degradation at high temperatures (i.e.,

[47] H2SO4 damages the pore walls of OMC and converts the material to amorphous carbon). Gou et al. studied the carbonization step at different temperatures (400, 600, 700, and 850 °C) and demonstrated that the optimum temperature for obtaining a highly ordered OMC is 400 °C. Interestingly, the sulfonation step

(carried out at 200 °C) indicated that calcination of the OMC at 850 °C resulted in the optimum carbonaceous material with retention of the porosity (Figure 5). Hara et al.[48] found that after carbonization,

OMC is converted to amorphous carbon in the sulfonation step. In addition, graphene sheets with high densities of -SO3H groups were also found.

Figure 5. TEM images of samples: (a and b) C600-3.5–2.0 M; (c) C600-4.0–2.0 M; (d) C600-4.5–2.0 M; (e) C600- 5.0–2.0 M (Reproduced from ref. [47]).

[38c] Dong and coworkers prepared OMC-SO3H in a three-step process using F127 as the SDA and FA as the carbon source (Figure 6). The OMP obtained from the first step was carbonized at various temperatures, and carbonization at 400 °C was found to afford a catalyst with higher acidity and catalytic activity towards the esterification of oleic acid with methanol.

[38c] Figure 6. Synthesis of MC-SO3H by a soft-templating approach (Reproduced from ref. ).

Hierarchical monolithic carbons with mesoporous arrays can also be prepared via a soft-templating approach.[49] These materials can be rapidly prepared on a remarkable scale, and they have promise for applications in catalysis[50] and separation and storage.[51] Mukai and Oginio[52] prepared a monolithic carbon from RF copolymerization and carbonization at 400-800 °C for 4 h followed by sulfonation using concentrated sulfuric acid at 80 °C for 10 h. This material was found to have a mesoporous structure as

This article is protected by copyright. All rights reserved proven by the N2 adsorption/desorption isotherm (Figure 7). The designed sulfonated monolithic carbon was successfully tested as catalyst in the liquid-phase esteriﬁcation of acetic acid with ethanol at 60 °C in a

ﬂow reaction system over 50 h of operation.

Figure 7. (a) SEM images for characterizing the CMHC. The inset shows a photograph of CMHC. Nitrogen adsorption data for the characterization of CMHC: (b) Adsorption (●) and desorption (○) isotherms, (c) mesopore size distribution calculated by applying the Dollimore-Heal equation to the adsorption isotherm (Reproduced from ref. [52]).

3.2. Sulfonated ordered mesoporous polymers (OMP-SO3H)

OMPs themselves can be independently designed as SAM catalysts for a number of acid-catalyzed reactions.[53] These polymers have a variety of structures that can bear various functionalities. Rapid syntheses and facile modification/functionalization are relevant advantages of OMPs. These OMPs can also be modified to have SO3H groups inside the pore walls. However, there are few reports of sulfonated OMPs

(OMP-SO3H). The porosity of OMPs is generated through a) the steric orientation and geometric structures of polymers (template-free method)[54] or b) the addition of a template during polymerization to replicate the template with a tunable and mesoscopic structure (templating method).[55] There are also other types of organic porous polymers featuring 2D or 3D networks with different pore sizes (metal-organic frameworks and microporous polymers).

[56] Ryoo and Choi synthesized an OMP-SO3H through a free-radical polymerization method starting from crosslinkable oleﬁnic monomers within the interstices of the porous templates in the presence of mesoporous silica KIT-6 as hard template for replication. The polymerization reaction proceeded under heating at 150 °C, and then the sulfonation step was conducted by heating the material with sulfuric acid to

OMP structures collapse when the pore diameters of the parent mesoporous silica are larger than the distance between the crosslinking points. Under the optimized replication conditions, the replica exhibited a very narrow pore size distribution and a high speciﬁc surface area, which is based on the structural standards

3 -1 of the parent silica template. This OMP-SO3H, with a surface area of 300 cm .g , was tested as a catalyst for the esterification of hexanoic acid with benzyl alcohol, and its catalytic activity was superior to that of commercially available Amberlyst-15, while its active acidic sites were weaker than those of Amberlyst-

15.[56]

Figure 8. (a) Synthesis of OMP-SO3H through poly-DVB using TMS-coated KIT-6 as the template. TEM images of (b) TMS-coated KIT-6 and (c) poly-DVB materials (Reproduced from ref. [56]).

Resol-based OMPs can be synthesized in the presence of hexamethyl tetraamine (HMTA) (OMR-

[HMTA]) as a crosslinking agent and F127 as the SDA.[57] HMTA inside the fabricated OMP can also be post-modified by 1,3-propansulfone through its free amine groups (Scheme 6), which finally leads to the formation of a zwitterion on the surface (quaternary amine cation and sulfonate anion). This zwitterionic mesoporous material can be converted in the subsequent step to an acidic SAM by adding CF3COOH, a strong acid. This route led to an ionic liquid anchored to the pore walls of OMR-[HMTA]. This catalyst was tested in the esterification of acetic acid with cyclohexanol, the hydration of propylene oxide, the Pechmann reaction of resorcinol with ethyl acetoacetate and the transesterification of tripalmitin with methanol, and it

This article is protected by copyright. All rights reserved showed remarkably superior activities to those of Amberlyst 15, sulfonic group-functionalized ordered mesoporous silicas, and acidic zeolites and comparable activities to those of sulfuric acid.[57]

[57] Scheme 6. Synthesis of OMP-SO3H/CF3SO3 based on HPTA (Reproduced from ref. ).

3.3. Sulfonated mesoporous composites

3.3.1. Sulfonated polymer-silica (SPS) mesocomposites

One of the methods for fabricating SPS mesocomposites is the ‘dissolution and entrapment’ method.[58] In this method, soluble polymer with a low degree of polymerization was added to the hydrolysis of the silica source (e.g., TEOS or TMOS) in the presence of an SDA. During the hydrolysis and formation of the silica network, polymer chains can be trapped within the wall of the mesoporous silica, which ultimately generates an SPS mesocomposite. In this manner, Wan et al.[59] incorporated MPTMS as an SAP to generate a sulfonated SPS composite using dissolution and entrapment method. Thus, TEOS and phenolic resin with a low degree of polymerization were employed as precursors, MPTMS was used for further conversion to -

SO3H groups, and F127 was used as the SDA. Interestingly, the authors did not use an organosiloxane coupling agent to couple the organic polymer and the SiO2, and instead, they take advantage of the coupling of Si to the -OH of resol during the final steps of the polymerization and TEOS hydrolysis. The polymer was hydrophobic, which enhanced its catalytic activity and decreased catalyst poisoning due to water. The catalyst was also successfully tested in the acetalization of ketones and in the condensation of acetone and phenol to yield bisphenol (Figure 9).[59]

Figure 9. Acetalization of carbonyl compounds catalyzed by silica-organic polymer based SAM (Reproduced from ref. [59]).

New hybrid hollow nanospheres containing silica and sulfonated polystyrene (PS-SO3H/PMA-SiO2) were designed and synthesized by Yang and coworkers, and the nanospheres aligned uniformly in the mesoporous channel of a silica shell.[60] The template components in this synthesis were polystyrene nanospheres and cetyltrimethylammonium bromide (CTAB). TEOS and Si-PMA were the precursors for the synthesis of the

SPS mesocomposite. Finally, after the synthesis of the hybrid hollow nanospheres, the template, CTAB, was extracted using EtOH/HCl. The obtained polymer-silica composite (PS/PMA-SiO2) then underwent sulfonation of the polystyrene moieties using chlorosulfonic acid (which has an acid exchange capacity in

−1 the range 0.8 to 2.0 mmol g ) to produce the SPS mesocomposite (PS-SO3H/PMA-SiO2). This catalyst was tested in the esterification of lauric acid with EtOH. To increase the surface hydrophobicity and consequently increase the catalytic activity, octyl organosilane chains were added in a post-modification step

(Figure 10).[60]

For comparison, corresponding free silica HN moieties were sulfonated by the same method and compared with PS-SO3H/PMA-SiO2 HNs in the esterification of lauric acid with ethanol. Additionally, this new catalyst was compared with the commercial Amberlyst®-15 catalyst. This new hybrid SPS showed higher catalytic activity than the other two catalysts, and the turnover frequency (TOF) of the optimized hybrid SPS was almost identical to that of concentrated sulfuric acid, which shows that the catalyst’s activity is similar to that of its homogeneous analog. The high activity of the hybrid HN moieties was attributed to the uniform distribution of sulfonic acid functionalities on the surface of the PS-SO3H nanospheres inside the 19

This article is protected by copyright. All rights reserved mesoporous silica shell, the penetrable mesochannels, and the suitable surface hydrophobicity, which increases the mass transfer. Furthermore, the recyclability of the hybrid HN moieties could be greatly enhanced by octyl group substitution, which may prevent the leaching of PS-SO3H during the catalytic process. For the synthesis of PS-SO3H/PMAn–SiO2-SO3H, different ratios (n) of PMA-Si to PS (n = 2.5,

3.3, and 5) were used to obtain different hybrid SPS HNs and to determine the effect of the ratio on the catalytic activity. Among the prepared materials, PS-SO3H/PMA2.5–SiO2-SO3H, which underwent octyl chain post-modification, was more active than non-octylated derivatives, samples prepared with other ratios

[60] and free sulfonated SiO2 HNs.

Figure 10. (a) Synthesis of PS-SO3H/PMAn–SiO2-SO3H, and TEM images of (b) PS-SO3H/SiO2 and (c) octylated PS- [60] SO3H/PMA2.5–SiO2-SO3H (reproduced from ref. ).

Polymerization of organic monomers inside of mesoporous silica materials has permitted reach into various functionalized polymer-silica composite materials with well-defined mesoporosities. Some ordered mesoporous silica materials contain disordered micropores within their walls. The structure and pore size range of the (micro)pores can play a crucial role in the polymerization mechanism inside the mesoporous silica materials and subsequent impact the stability of the polymer/silica mesocomposites. Ryoo and coworkers[61] synthesized two different SBA-15 silica mesoporous materials containing different pore sizes.

The pore size could be fine-tuned to 2-4 nm when the molar ratio of SiO2/P123 was 45, while a further increase in this ratio to 75 essentially rendered porous materials with pore sizes > 2 nm. Based on XRD analyses, their prepared materials exhibited better compatibility with SBA-15 in r = 45. The location of the

This article is protected by copyright. All rights reserved polymers was systematically controlled by adjusting the micropores of the silica framework and the polymerization conditions (Figure 11). They used various vinyl monomers, such as styrene, chloromethyl styrene, 2-hydroxyethyl methacrylate, and methacrylic acid, for the polymerization inside the mesoporous silica. Among these monomers, styrene and divinylbenzene with AIBN inside the SBA-15 provided the optimum results, and subsequent sulfonation was conducted using concentrated sulfonic acid. This sulfonated mesocomposite was then tested as a catalyst in the esterification of benzyl alcohol with hexanoic acid in toluene at 75 °C.[61]

Figure 11. (a) Controlled polymerization of organic polymers inside the micropores. (b) XRD patterns of SBA-15 and polymerization-controlled mesoporous silica SBA-15 (PCMS/SBA-15). (c) BET analyses of SBA-15 and PCMS/SBA-15 (Reproduce from ref. [61]).

A similar strategy was also devised to synthesize a sulfonated mesocomposite polymer/silica while maintaining the main structure of the mesopores and the porosity.[62] To generate such materials, they used divinylbenzene (DVB) and sodium p-styrene sulfonate as the monomers for the copolymerization on the surface of mesoporous silica under solvothermal conditions (Figure 12). This polymer made the surfaces of the pores hydrophobic (as determined by contact angle analysis) during sulfonation. This hydrophobicity significantly reduced catalyst poisoning by water. The mesocomposite exhibited high stability (372 °C)

This article is protected by copyright. All rights reserved according to TG analysis and an excelling catalytic performance in the esterification of acetic acid with cyclohexanol, and 1-butanol and the condensation of benzaldehyde with ethylene glycol making this

[62] material remarkably more active than Amberlyst 15, SBA-15-Pr-SO3H, and homogeneous H2SO4.

Figure 12. Copolymerization of divinylbenzene (DVB) and sodium p-styrene sulfonate on the surface of mesoporous silica to produce a hydrophobic organic polymer-silica composite-based SAM (Reproduced from ref. [62]).

3.3.2. Sulfonated carbon-silica (SCS) mesocomposites

A facile template carbonization strategy to synthesize ordered large-pore mesoporous silica microspheres with sulfonated carbon nanoparticles trapped inside accessible mesopores through a solvent- evaporation-induced aggregating assembly (EIAA) approach is an interesting route towards the design of advanced carbon-silica-based composites of SAMs. In this approach, amphiphilic poly(ethylene oxide)-b- polystyrene (PEO-b-PS) and TEOS were used as the template and silica source, respectively. However, the template was also used as the carbon source for the mesoporous structure. The synthesis of carbon/silica mesocomposites requires several consecutive steps including a) hydrolysis and condensation of TEOS with silica in the presence of PEO-b-PS, b) hydrothermal aging of the material obtained in the first step, c) in situ carbonization of PEO-b-PS to generate carbon nanoparticles within the mesoporous structure, and finally, d) sulfonation of the obtained carbon-silica mesocomposite to produce a new SAM. PEO-b-PS molecules are employed not only as a template for the creation of uniform mesopores but also for the production of carbon nanoparticles in the mesopores. This protocol provides an alternative approach that avoids the use of organic templates by introducing other external carbon sources. This unique mesocomposite structure with a 22

This article is protected by copyright. All rights reserved microsphere shape and abundant SO3H groups exhibited excellent catalytic activity in the condensation of benzaldehyde with ethylene glycol (93% conversion) and good reusability (Figure 13).[63]

Figure 13. Catalysis by template-carbonized SASM (Reproduced from ref. [63]).

Viswanadham and coworkers[64] prepared a new sulfonated silica/carbon mesocomposite through template carbonization in which glucose was selected as both the template and carbon source. Sulfuric acid was added to the glucose/TEOS reaction mixture to hydrolyze and sulfonate the carbonaceous part, which was subsequently converted to the SCS mesostructure via carbonization under a N2 atmosphere (Scheme 7).

Although the sulfonated mesocomposite possesses a less ordered mesopore structure, it exhibited efficient catalytic activity in the butylation of phenol. The hydrophilicity of the sulfonic acid linked to hydrophobic carbon can lead to strong interactions with the hydrophilic surface of the silica. Another interesting feature of this work was the surfactant-free synthesis and the ready availability of glucose in the synthesis of the mesocomposite.

Scheme 7. Use of glucose as both the template and carbon source for the production of sulfonated silica/carbon mesocomposites (Reproduced from ref. [64]).

This article is protected by copyright. All rights reserved Magnetic separation can also offer additional advantages for certain types of materials/catalysts in terms of recovery/separation from the reaction mixture after the reaction. In this regard, an advanced, new sulfonated magnetic spherical silica/carbon mesoporous composite was synthesized by a simple route[65] as indicated in Figure 14. First, the silica layer encapsulated the magnetic core (Fe3O4), and that layer was covered by another carbon layer created via carbonization of the absorbed glucose in the material as the carbon source. After the successful modification with -SO3H, a solid acid composite carbonized at a low temperature (400 °C) exhibited the highest acidity (1.98 mmol H+). The high surface area, large pore volume and high acidity gave this solid acid material excellent catalytic activity in the transesterification of soybean oil with methanol.[65]

Figure 14. (a) Synthesis of Fe3O4@SiO2@PCS. TEM images of the core/shell structure of (b) Fe3O4@SiO2 and (c) [65] Fe3O4@SiO2@C (Reproduced from ref. ).

Sugar-derived amorphous carbonaceous materials bearing -SO3H groups cannot catalyze water- sensitive reactions such as the dimerization of α-methylstyrene because of their small surface areas (Figure

15). Furthermore, these solid acid catalysts also suffer from significant leaching and deactivation that has not yet been addressed. To solve these issues, a composite of amorphous sulfonated sugar-derived carbon within mesoporous silica was designed and was reported to exhibit remarkable catalytic activity in the dimerization of α-methylstyrene. Under the optimized conditions, the selectivity for unsaturated dimers in the presence of catalyst exceeded 98%. The authors also demonstrated that SO3H groups occupy a large 24

This article is protected by copyright. All rights reserved portion of the surface area of the amorphous carbon inside the pores thus preventing the production of side products i.e., intramolecular Friedel-Crafts alkylation, leading to high catalytic activity and selectivity.[38d]

Figure 15. Composite of amorphous sulfonated carbon inside of mesoporous silica (Reproduced from ref. [38d]).

3.4. Sulfonated periodic mesoporous organosilicas (PMO-SO3H)

In the development of SAMs as catalysts, many studies have been conducted on their hydrophobicity as this parameter plays a crucial role in the catalytic activity of solid acid catalysts especially when the reactants are hydrophobic (i.e., in fatty acid transesterification reactions).[66] Traditional SASMs could be transformed into compatible hydrophobic SASMs through the incorporation of a hydrophobic SAP or surface modification with alkyl or phenyl chains.[4b, 67] However, these methods have some drawbacks, including decreasing the pore size and consequently causing molecular transfer limitations in the cases of bulky compounds, which can be detrimental for the performance of such materials.[4b]

Periodic mesoporous organosilicas can be considered next-generation SASMs with sufficient hydrophobicity and crystal-like pore walls, and they were first reported by Inagaki and coworkers.[68] The first sulfonated benzene-bridged PMO (Ph-PMO-SO3H) was synthesized via the condensation of 1,4- bis(triethoxysilyl)benzene (BTEB) with an SDA. The obtained white solid was then sulfonated with 25%

SO3/H2SO4 solution. Then, the same group was simultaneously condensed with both BTEB and MPTMS under basic conditions in the presence of an SDA to fabricate a Ph-PMO with sulfonic acid groups.[69] The oxidation of the -SH groups, which are produced in the first step, to -SO3H groups on the surface of the Ph-

PMO can be achieved by treatment with concentrated HNO3 at room temperature for 24 h.

This article is protected by copyright. All rights reserved [70] Fukuoka and coworkers hydrolyzed starch in water using two water-tolerant PMO-SO3H materials, ethylene-bridged (Et-PMO) and phenylene-bridged compounds, and this was the first report of using this type of catalyst in an aqueous reaction of this kind.[70] Jerome and coworkers[71] reported the catalytic application of Ph-PMO-SO3H in two different reactions including the synthesis of bis(indolyl)methanes from aromatic aldehydes and indole and the mono-etherification of glycerin with 1-phenylpropan-1-ol under aqueous conditions.

Cho and coworkers studied the possibility of directly synthesizing 2D hexagonal (p6mm) Ph-PMO-

SO3H mesostructures via the condensation of BTEB and MPTMS in the presence of H2O2 using P123 under

[72] dilute acidic conditions. Sulfonic acid groups (-SO3H) were successfully generated in situ by the oxidation of -Pr-SH using H2O2 as the oxidant during the synthesis of the sol-gel. The SEM image showed that Ph-PMO-SO3H existed as spheres with diameters of 2-5 μm (Figure 16).

Figure 16. (a) TEM and (b) SEM images of 2D hexagonal (p6mm) Ph-PMO-SO3H (Reproduce from ref.

[72]).

The proposed approach was further expanded to the design of Ph-PMO-SO3H mesostructures with 3D cubic (Pm3n symmetry) structures using a highly acidic medium and CTAB as the SDA (Figure 17a and b).[73] In this work, BTEB was condensed with the optimum amount of MPTMS. Ordered and uniform mesopores could be obtained by using up to 25 mol% of MPTMS in the initial reaction mixture. The chemical structures of the precursor and the SDA had dramatic effects on the mesostructure. Similarly, another 3D (Pm3n) cubic Ph-PMO-SO3H was prepared by using a novel allylorganosiloxane precursor, 1,4- bis(triallylsilyl)phenylene, and cetyltrimethylammonium chloride (C16TMACl) as the SDA in an acidic 26

This article is protected by copyright. All rights reserved medium.[74] This PMO was particularly efficient in Friedel-Crafts acylation reactions and in controlling the atmospheric emission of volatile organic compounds that are responsible for ground-level ozone, air toxicity and smog (Figure 17c-f). Sulfonation of the phenylene bridges was performed using concentrated sulfuric acid.

Figure 17. (a) TEM and (b) SEM images of the Ph-PMO-SO3H mesostructure with a 3D cubic (Pm3n symmetry) structure. (c) TEM and (d-e) SEM images of 3D (Pm3n) cubic Ph-PMO-SO3H prepared using a novel allylorganosilane precursor, 1,4-bis(triallylsilyl)phenylene, and C16TMACl. (f) Friedel-Crafts acylation over the 3D cubic phenylene-bridged mesoporous silica (Reproduced from ref. [73-74]).

Ph-PMOs have good thermal stability especially in the presence of air because phenyl groups are easily oxidized, and therefore, the structure of their sulfonated derivatives are maintained at higher temperatures.

In addition, the stability of Ph-PMOs under N2 is remarkably higher than their stability under air. The thermal stability of Ph-PMO has been extensively studied by TGA.[75] Accordingly, decomposition of the phenyl groups is observed from 500-700 °C. Ph-PMO sulfonated with chlorosulfonic acid was further tested in the esterification of acetic acid with ethanol. The authors claimed that the Ph-PMO synthesized via the self-assembly of Brij76 and BTEB should be calcined under a N2 atmosphere, and structural changes were observed with increasing calcination temperatures.[75]

Additionally, the use of acidic SBA-15-like PMOs, in which the location of the acid sites can be controlled, in acid-catalyzed reactions in hot water (i.e., the hydrolysis of cellobiose) has also been proposed.[76] The hybrid silica was prepared by the condensation of BTEB. The material was sulfonated

This article is protected by copyright. All rights reserved using chlorosulfonic acid or 3-mercaptopropyltrimethoxysilane and further oxidized with H2O2 to afford materials containing Bronsted acid sites, and were fully characterized. The acidic features of the materials were characterized by calorimetry of the adsorption of ammonia. Furthermore, the catalytic potentials of the materials were tested in the gas-phase dehydration of isopropanol as a model reaction and compared with the reference acidic sulfonated resin, Amberlyst 15. The introduction of -Pr-SO3H by the oxidation of -PrSO3H groups using H2O2 did not change the mesoscopic structure, while sulfonation with chlorosulfonic did change the mesoscopic structure. However, the results of the ammonia adsorption calorimetry indicated the heterogeneity of this solid acid, confirming that there are distinct sulfonation sites. This conclusion was also supported by XPS analysis.

In the gas-phase dehydration of isopropanol, the solids sulfonated with chlorosulfonic acid exhibited a catalytic activity equivalent to that of Amberlyst 15, but they were less stable due to leaching of the sulfur species. SBA-15-like PMOs obtained by H2O2 oxidation of the -SH groups were less acidic and showed lower catalytic activity in the gas-phase dehydration of isopropanol. However, no significant sulfur leaching was observed for this catalyst. The catalytic activities of these materials were also tested in a biomass valorization such as in cellobiose hydrolysis in hot water. The solids were active at 150 °C; however, a remarkable amount of sulfur leaching was observed, and therefore, the reaction proceeded mainly homogeneously, especially with the chlorosulfonic acid-modified material. The author found that a pretreatment step including the hot washing of catalysts containing Pr-SO3H moieties lead to a decrease in their activities in hydrolysis reactions and increases in their stability and recyclability (Scheme 8).[76]

[76] Scheme 8. Synthesis of double sulfonated phenylene-bridged PMO-SO3H.

Bion and coworkers also studied four different types of SASMs and monitored the catalytic activities in the aqueous synthesis of bis(indolyl)methanes. They extensively studied the effect of hydrophobicity on the catalyst activities and found that an increase in hydrophobicity enhanced the catalytic efficiency.[77]

After the calculation of the TOFs, they demonstrated that among all the samples, Ph-PMO-Pr-SO3H exhibited the highest catalytic activity, TOF, yield, and H+ exchange capacity. Embedding the phenyl groups within the pore walls can significantly increase the hydrophobicity relative to the corresponding SBA-15-

PrSO3H. This result was obtained based on the adsorption behavior of toluene/water over both SASMs. The

TOF was highly dependent on the -SO3H loadings. Therefore, increasing the -SO3H loading improved the catalytic activity of the systems. The authors claimed that silylation of the silanol groups increased the hydrophobicity and consequently improved the catalytic efficiency (Scheme 9).[74]

Scheme 9. Comparing the catalytic activities of four different types of sulfonated mesoporous materials.[74]

Ferreira and Jérôme[78] extensively studied the effects of various parameters on the catalytic activity of

Ph-PMO-SO3H including the effects of the density and the location of -SO3H groups and the hydrophobicity on the conversion of fructose to 5-hydroxymethylfurfural (HMF). The series of synthesized catalysts were contained phenylene and biphenylene bridges. In addition, the sulfonation was achieved by two different methods: the first is the sulfonation of the benzene rings with sulfuric acid and the second is via condensation with MPTMS and subsequent oxidation to sulfonic acid. Among the various loadings of sulfonic acid sites, 0.36 mmol g-1 was reported to be the optimum loading for sulfonated PMOs. In addition, of the two sulfonation methods, propylsulfonic acid linkers resulted in catalysts with higher activity in the conversion of fructose to HMF. A comparison between BTEB and 4,4′-bis-(triethoxysilyl)biphenyl

(BTEBP) bridges indicated that the phenylene bridge provided superior activity compared to the biphenylene bridge (Figure 18).

[78] Figure 18. Using Ph-PMO-SO3H for HMF production (Reproduce from ref. )

[79] Yang and coworkers also prepared a new Ph-PMO-SO3H bearing aliphatic chains between the Si and benzene. 1,4-Bis(trimethoxysilylethyl)benzene (BTSEB) was employed as an organic moiety in the PMOs and was condensed with TMOS. The authors claimed obtain highly ordered PMOs was difficult due to the long chain and flexible organic group in BTSEB when it was utilized in the absence of TMOS. In the second step, the prepared Ph-PMO was sulfonated with chlorosulfonic acid, and the resulting catalyst was successfully employed in the esterification of hexanoic acid with ethanol (Scheme 10). In the synthesis of the catalyst, two molar percentages of BTSEB in the TMOS/BTSEB mixture were 30 and 70 mol%. The mesostructure generated with 70% BTSEB was relatively collapsed, while in the material prepared with

30% BTSEB, the mesostructure was retained. In most cases, increasing the molar ratio of the organic bridge leads to the deterioration of the mesostructure. However, in this work, under similar conditions, 30 mol% of

BTSEB as the bridge resulted in a lower catalytic activity than that of the material prepared with 70 mol%

BTSEB. This observation can be attributed to the high concentration of sulfonate groups in the 70 mol% material via the phenylene bridges on the surface.[79]

Scheme 10. Sulfonation of the aliphatic chain-containing Ph-PMO for esterification reactions.[79]

Kaliaguine[80] synthesized a series of ethylene-bridged PMOs with different amounts of sulfonic acid via the condensation of MPTMS with bis(trimethoxysilyl)ethane (BTME) under basic conditions in the presence of cetyltrimethylammonium chloride (CTAC) as the SDA. The obtained SASM had an ordered

Pm3n cubic-like mesostructure with a high surface area (up to 950 m2/g) and narrow pore size distribution

(up to 3.50 nm). The order of the structural was retained during oxidation. This group also examined the effects of the amount of MPTMS (15, 25, 50 mol% of MPTMS in PMO) on the structural properties, morphology, and thermal behavior of the material. With 15 mol% of MPTMS, the morphology, XRD pattern, and BET results were similar to those of the parent mesopore structure, while with 50 mol% of

MPTMS, a significant deformation of the morphology and a decrease in the intensity of the peak at 2θ ~ 2° was observed. This observation indicates that by increasing the amount of MPTMS to 50 mol%, a significant loss of mesostructural ordering occurred. In the case of 50 mol%, other diffraction peaks also disappeared, probably due to the decreased mesostructural ordering by the functionalization.

As mentioned discussed in the context of traditional SASMs, researchers tend to improve the catalytic efficiency of SASMs through the incorporation of additional group(s), making them bifunctionalized materials. For instance, -SO3H is widely used in the presence of amine-type functionalities to improve the catalytic behavior. Shylesh and Thiel’s groups[81] introduced amine groups via post-modification of BTEB- based PMO-SO3H to obtain bifunctionalized PMO-based systems. To achieve bifunctionalization, they first condensed BTEB with Boc-protected APTS and then sulfonated the intermediate with chlorosulfonic acid.

The results showed a quantitative product conversion with 97.5% yield. The authors also tested the catalytic activity of N-protected PMO-SO3H/-NHBoc in this a nitroaldol condensation, and they observed no conversion. However, the protected system exhibited remarkable activity in the conversion of dimethoxyphenylmethane to benzaldehyde and provided the target product in quantitative yield. This catalytic system was also compared with monofunctionalized mesoporous materials (SBA-NH2 and PMO-

SO3H), and the results indicated PMO-SO3H/-NH2 was more efficient in this reaction. The protons from the

-SO3H groups in these mesostructured materials can be exchanged with positively charged materials. This method is an alternative and useful strategy for immobilizing anionic and even bulkier catalytically active species.[82] On the other hand, sulfonate groups can act as a ligands to immobilize transition metals. Zhang

[83] and Li used Ph-PMO-SO3H to electrostatically immobilize Sc(OTf), a catalytically active transition metal, through chelation with the -SO3H moieties (Scheme 12) to generate an appropriate hybrid catalyst for

Mukaiyama-aldol reactions. The superior catalytic activity of this material was correlated to the mesoporosity and hydrophobicity of the pore walls due to the presence of embedded phenyl moieties.

Scheme 11. Synthesis of a bifunctionalized acid-based PMO to catalyze nitroaldol reactions.[81]

[83] Scheme 12. Supporting Sc(OTf)2 on sulfonated Ph-PMO.

[84] Inagaki and coworkers synthesized the first biphenylene-bridged PMO (biPh-PMO-SO3H) in 2002,

[85] and then they separately functionalized biPh-PMO-SO3H and Ph-PMO-SO3H using a new approach.

Their methodology involved a post-functionalization with two organosilane epoxides and subsequent treatment with sulfite to produce a new series of PMO-SO3H derivatives. The catalytic activities of the newly synthesized PMO-SO3H materials were investigated in the esterification of acetic acid with ethanol, the acylation of benzyl alcohol with acetic acid and the condensation of phenol with acetone (Scheme

13).[85] When comparing the catalytic activities of these four catalysts with those of previously reported catalysts, including MCM-SO3H and Ph-PMO, which were both sulfonated by conc. sulfuric acid and

MPTMS through both grafting and condensation approaches. Indeed, testing the catalysts in the esterification of acetic acid with ethanol indicated that the new biphenylene-bridged PMOs, including BiPh-

PMO-CySO3H and Ph-PMO-GlySO3H, are the most active catalysts among those tested for this reaction.

For instance, these new phenylene-based PMOs were more active catalysts than those that were sulfonated by conc. sulfuric acid. These observations indicate that the new SAPs are more efficient than traditional

SAPs such as MPTMS and conc. sulfuric acid.[85]

Imidazolium ionic liquid-PMO (IL-PMO) is a type of mesostructure in which the imidazolium salt is embedded inside the PMO framework, and they were first designed by Karimi and coworkers.[86] Elhamifar and Karimi[87] modified imidazolium-based IL-PMOs by grafting MPTMS onto their surface and then oxidizing them to generate -Pr-SO3H groups on the modified surface. The catalytic activities of these compounds were then tested in the esterification of various alcohols and acids at room temperature, and good to high yields were observed. The TEM images indicated that this modification did not significantly influence the mesoscopic structure of the IL-PMO (Scheme 14). In another work, the same group synthesized this material by the condensation of TMOS, MPTMS, and the IL bridge in the presence of P123 as a surfactant. The sulfonic acid groups present in the ionic framework of the imidazolium chloride were highly active. This catalyst had higher recyclability and shorter reaction times than the corresponding

SASMs in Biginelli reactions for the synthesis of dihydropyrimidinones (Scheme 14). Condensation with

TMOS did not negatively impact the hexagonal array of the mesoporous organosilica.[88]

Scheme 14. Imidazolium-bridged PMO sulfonated by MPTMS as a catalyst for Biginelli and esterification reactions (Reproduce from ref. [87]).

This article is protected by copyright. All rights reserved Additionally, a new and straightforward post-synthetic method involving the use of mercaptol/H2O2 or concentrated H2SO4 for the sulfonation of the ethylene groups of ethylene-PMO to generate a new type of

[93] PMO-SO3H was recently developed. Synthesized hexagonal mesoporous material with ethenylene-silica pore walls was obtained by with different pore size distributions using different SDAs (P123, Brij76, and

Brij56). For the sulfonation, the ethylene groups were first converted to epoxides by epoxidation at 5 °C.

The resulting epoxides sulfonated to generate HME-SO3H, a β-hydroxysulfonic acid, in the presence of bisulfite ions at 65 °C. The catalytic activity of HME-SO3H was tested in the esterification of acetic acid with ethanol at 70 °C for 24 h. The epoxidation step was hypothesized to play a crucial role in determining the yield of -SO3H groups attached to the silica surface. Therefore, they optimized temperature, oxidant, pH, water content and reaction time in the epoxidation reaction (Scheme 15).

Scheme 15. Sulfonation of vinylene-bridged PMO by epoxidation followed by nucleophilic attack of the ring by sulfite.[93]

[94] Kondo and coworkers also prepared a new type of PMO-SO3H by the Diels-Alder reaction of the ethenylene groups on the framework of hybrid mesoporous ethenylene-silica (HME) with pendant phenylene groups followed by sulfonation with concentrated H2SO4. The catalytic activity of this hybrid mesostructure was investigated in three types of reactions, including the esterification of acetic acid and

Beckmann and pinacol-pinacolone rearrangements. The activity of Ph-SO3H HME was compared with those of various other catalysts such as H-Beta, H-ZSM5, H3PW12O40, Amberlyst 15, p-TsOH, and Nafion-H

(NR50), and PMO showed superior selectivities and conversions compared to the other catalysts in the

[95] with HME (Scheme 16) also led to a new Ant-HME-SO3H material, which was also successfully employed in the esterification of acetic acid with ethanol.

Scheme 16. Sulfonation of post-synthesized vinylene bridged PMO by using Diels-Alder reaction.[95]

This article is protected by copyright. All rights reserved a simple approach for the preparation of a new class of bifunctionalized PMO-SO3H materials featuring partly unoxidized thiol groups was also recently disclosed.[96] Au nanoparticles could be synthesized within the pores of PMO which contains -SH functionalized groups and in situ Au3+ reduction inside the pores under acidic conditions. Au nanoparticles with a uniform, narrow size distribution of approximately 1-2 nm, which is of great significance for catalytic reactions, could indeed be produced within Et-PMO-SH/SO3H materials (Scheme 17). This group investigated the synthesized catalysts in a number of reactions including alkyne hydration, intramolecular hydroamination, styrene oxidation and three-component coupling reactions. The amphiphilicity of the Et-PMO-SO3H/-SH/Au nanostructures enabled the organic reactions to be performed efficiently in pure water with no organic cosolvent. The catalyst recyclability highlighted the possibility of reusing the catalysts at least 10 times without appreciable loss of catalytic efficiency in the model reactions.[96]

Scheme 15. Bifunctional thiol-sulfonic acid-based Et-PMO that can catalyze multiple organic reactions.[96]

[89] An uniform distribution of SO3H groups is crucial for certain applications e.g., in PEM fuel cells. One of the most interesting works in the field of PMO-SO3H materials is the design of uniformly distributed PMO-

[91] location of the -SO3H groups has a substantial impact on the catalytic activity of the SASMs. In this method, generating the appropriate number of bridged sulfides is essential for obtaining a nanoporous structure.[33a] Romero-Salguero and coworkers[33a] designed two types of SASMs with highly distributed tetrasulfide-bridged linkers that were synthesized by the condensation of bis[3-(triethoxysilyl)propyl]tetrasulfide with TEOS or BTEB under acidic conditions in the presence of

Brij76 as the SDA. Hydrogen peroxide was then selected to convert the tetrasulfides to sulfonic acid groups.

In this regard, sulfonic acids were uniformly distributed over the framework. The authors claimed that increasing the S content in the syntheses of these SASMs caused significant erosion of the mesoscopic structure. Therefore, with a lower tetrasulfide content, a more ordered mesoscopic structure was obtained

(Scheme 18).

The optimized derivative of this SASM was employed in the esterification of acetic acid with ethanol, and the results indicated that the activities of PMO-SO3H materials and Amberlyst-15 were comparable.

Scheme 19. Synthesis of bifunctionalized disulfide-bridged sulfonated PMOs with amine functionalities.[33b, 90]

Mehdi and coworkers[33b, 90] also synthesized a bifunctionalized PMO containing disulfide groups within the framework and propyl amine moieties on the surface. The sulfides were then converted into -SO3H groups through one sequential reduction and oxidation processed using NaBH4 and H2O2, respectively

(Scheme 19). Similar mesoporous organosilica materials with disulfide bridges, bis[3-

(triethoxysilyl)propyl]disulﬁde (BTPDS), were also prepared and chemically oxidized to generate sulfonic acid groups.[92] The ratio of BTPDS to TMOS was found to be crucial to the mesoscopic structure of the mesoporous organosilica. For example, by increasing the molar ratio of BTPDS, the mesostructure shifts from a 2D hexagonal structure to a cellular foam-like structure. The structural characterization after the oxidation showed that a remarkable change occurred in the mesostructure especially when the molar ratio of

Figure 19. Effect of the TMOS:BTPDS ratio on the porous structure of PMO. Molar ratios of (a) 10; (b) 10-SO3H; (c) [92] 20; (d) 20-SO3H; (e) 30; (f) 30-SO3H; (g) 40; and (h) 40-SO3H (Reproduce from ref. ).

Several SAMs that can be sulfonated by various approaches are discussed and reviewed in this paper. Due to presence of sulfonic acid functionalities, these SAMs are promising candidates for solid Bronsted acid catalysts for organic transformations. Therefore, several SAPs and their applications, features and properties were discussed in terms of their use in the further modification of mesoporous materials. In addition, the catalytic power and applications of these SAMs, which are reported for a variety of catalyzed reaction, were addressed. Sulfonation can provide a rapid method of manufacturing catalytically effective mesopores.

Moreover, sulfonic acid groups on the surface of mesopores can act as active and stable Bronsted acid sites to catalyze a wide range of organic reactions. Additionally, the newly developed SAMs that were mentioned in this article may have more opportunities for further investigation.

This article is protected by copyright. All rights reserved 5. Abbreviation ATPS aminopropyltrialkoxysilane TOF turnover frequency PMO periodic mesoporous organosilica SDA structure directing agent BTEB 1,4-bis(triethoxysilyl)benzene BTEBP 4,4′-bis-(triethoxysilyl)biphenyl PEG polyethylene glycol IL ionic liquid HMF 5-hydroxymethylfurfural TEOS tetraethylorthosilicate TMOS tetramethylorthosilicate MPTMS 3-mercaptopropyltrimethoxysilane SASM sulfonic acid-based silica mesostructure SACM sulfonic acid-based carbon mesostructure SAM sulfonic acid-based mesostructure SAP sulfonic acid-based precursor HME hexagonal mesoporous ethenylene-silica AIBN azobisisobutyronitrile CTAB cetyltrimethylammonium bromide Boc tert-butyloxycarbonyl BTSEB 1,4-bis(trimethoxysilylethyl)benzene BTME bis(trimethoxysilyl)ethane CTAC cetyltrimethylammonium chloride SCS sulfonated carbon-silica SAL sulfonic acid linker Si-PMA alkoxysilylated poly(methyl acrylate)

This article is protected by copyright. All rights reserved 5. Reference [1] a) F. Guo, Z. Fang, C. C. Xu, R. L. Smith Jr, Prog. Energy Combust. Sci. 2012, 38, 672-690; b) Y. M. Sani, W. M. A. W. Daud, A. R. Abdul Aziz, Appl. Catal., A 2014, 470, 140-161; c) H. Li, H. Wu, Q. Zhang, J. Liu, X. Liu, Y. Liu, S. Yang, Curr. Catal. 2013, 2, 173-212; d) T. Okuhara, Chem. Rev. 2002, 102, 3641-3666. [2] A. El Kadib, A. Finiels, D. Brunel, Chem. Commun. 2013, 49, 9073-9076. [3] A. S. Dias, M. Pillinger, A. A. Valente, J. Catal. 2005, 229, 414-423. [4] a) S. Rostamnia, E. Doustkhah, Synlett 2015, 26, 1345-1347; b) B. Karimi, D. Zareyee, Org. Lett. 2008, 10, 3989-3992. [5] a) S. Rostamnia, E. Doustkhah, RSC Adv. 2014; b) S. Rostamnia, A. Zabardasti, J. Fluorine Chem. 2012, 144, 69-72; c) S. Rostamnia, F. Pourhassan, Chin. Chem. Lett. 2013, 24, 401-403; d) S. Rostamnia, H. Xin, X. Liu, K. Lamei, J. Mol. Catal. A: Chem. 2013, 374–375, 85-93; e) S. Rostamnia, E. Doustkhah, Tetrahedron Lett. 2014, 55, 2508-2512; f) S. Rostamnia, N. Nouruzi, H. Xin, R. Luque, Catal. Sci. Technol. 2015, 5, 199-205; g) S. Rostamnia, E. Doustkhah, A. Nuri, J. Fluorine Chem. 2013, 153, 1-6. [6] a) M. H. Lim, C. F. Blanford, A. Stein, Chem. Mater. 1998, 10, 467-470; b) W. M. Van Rhijn, D. E. De Vos, B. F. Sels, W. D. Bossaert, Chem. Commun. 1998, 317-318; c) W. V. Rhijn, D. D. Vos, W. Bossaert, J. Bullen, B. Wouters, P. Grobet, P. Jacobs in Studies in Surface Science and Catalysis, Vol. 117 (Eds.: F. B. C. D. S. G. L. Bonneviot, S. Kaliaguine), Elsevier, 1998, pp. 183-190. [7] a) I. Díaz, F. Mohino, J. Pérez-Pariente, E. Sastre, P. A. Wright, W. Zhou in Studies in Surface Science and Catalysis, Vol. 135 (Eds.: F. F. F. D. R. A. Galarneau, J. Vedrine), Elsevier, 2001, pp. 252; b) I. Díaz, F. Mohino, E. Sastre, J. Pérez-Pariente in Studies in Surface Science and Catalysis, Vol. 135 (Eds.: F. F. F. D. R. A. Galarneau, J. Vedrine), Elsevier, 2001, pp. 285; c) F. Mohino, I. Díaz, J. Pérez- Pariente, E. Sastre in Studies in Surface Science and Catalysis, Vol. 142 (Eds.: G. G. R. Aiello, F. Testa), Elsevier, 2002, pp. 1275-1282; d) D. Margolese, J. A. Melero, S. C. Christiansen, B. F. Chmelka, G. D. Stucky, Chem. Mater. 2000, 12, 2448-2459; e) K. Wilson, A. F. Lee, D. J. Macquarrie, J. H. Clark, Appl. Catal., A 2002, 228, 127-133; f) R. van Grieken, J. A. Melero, G. Morales in Studies in Surface Science and Catalysis, Vol. 142 (Eds.: G. G. R. Aiello, F. Testa), Elsevier, 2002, pp. 1181- 1188; g) M. Boveri, J. Aguilar-Pliego, J. Pérez-Pariente, E. Sastre, Catal. Today 2005, 107–108, 868- 873; h) D. Mauder, D. Akcakayiran, S. B. Lesnichin, G. H. Findenegg, I. G. Shenderovich, J. Phys. Chem. C 2009, 113, 19185-19192. [8] J.-P. Dacquin, H. E. Cross, D. R. Brown, T. Duren, J. J. Williams, A. F. Lee, K. Wilson, Green Chem. 2010, 12, 1383-1391. [9] W. D. Bossaert, D. E. D. Vos, W. M. V. Rhijn, J. Bullen, P. J. Grobet, P. A. Jacobs, J. Catal. 1999, 182, 156-164. [10] J. A. Melero, R. V. Grieken, G. Morales, Chem. Rev. 2006, 106, 3790-3812. [11] J. N. P rez-Pariente, . D az, . ohino, . Sastre, Appl. Catal., A 2003, 254, 173-188. [12] G. H. Mahdavinia, H. Sepehrian, Chin. Chem. Lett. 2008, 19, 1435-1439. [13] a) R. v. Grieken, J. A. Melero, G. Morales, Appl. Catal., A 2005, 289, 143-152; b) W. Zhao, P. Salame, F. Launay, A. Gédéon, Z. Hao, J. Porous Mater. 2008, 15, 139-143. [14] D. Srinivas, L. Saikia, Catal. Surv. Asia 2008, 12, 114-130. [15] M. A. Naik, D. Sachdev, A. Dubey, Catal. Commun. 2010, 11, 1148-1153. [16] G. M. Ziarani, A. Badiei, M. S. Nahad, M. Hassanzadeh, Eur. J. Chem. 2012, 3, 433-436. [17] S. Sreevardhan Reddy, B. David Raju, V. Siva Kumar, A. H. Padmasri, S. Narayanan, K. S. Rama Rao, Catal. Commun. 2007, 8, 261-266. [18] R. I. Kureshy, I. Ahmad, K. Pathak, N. H. Khan, S. H. R. Abdi, R. V. Jasra, Catal. Commun. 2009, 10, 572-575. [19] Y. Zheng, X. Su, X. Zhang, W. Wei, Y. Sun in Studies in Surface Science and Catalysis, Vol. 156 (Eds.: S. Abdelhamid, J. Mietek), Elsevier, 2005, pp. 205-212. [20] G. Mohammadi Ziarani, S. Faramarzi, N. Lashgari, A. Badiei, J. Iran Chem. Soc. 2014, 11, 701-709. [21] a) D. Zareyee, B. Karimi, Tetrahedron Lett. 2007, 48, 1277-1280; b) B. Karimi, D. Zareyee, Tetrahedron Lett. 2005, 46, 4661-4665; c) D. Zareyee, M. A. Khalilzadeh, Int. J. Green Nanotechnol. 2012, 4, 377-384; d) D. Zareyee, M. A. Khalilzadeh, Int. J. Green Nanotechnol. 2012, 4, 289-295; e) O.

This article is protected by copyright. All rights reserved Kister, F. Roessner, J. Porous Mater. 2012, 19, 119-131; f) I. K. Mbaraka, K. J. McGuire, B. H. Shanks, Ind. Eng. Chem. Res. 2006, 45, 3022-3028. [22] a) A. Rostami, B. Tahmasbi, H. Gholami, H. Taymorian, Chin. Chem. Lett. 2013, 24, 211-214; b) K. Niknam, N. Jafarpour, E. Niknam, Chin. Chem. Lett. 2011, 22, 69-72; c) S. R. Jetti, A. Bhatewara, T. Kadre, S. Jain, Chin. Chem. Lett. 2014, 25, 469-473; d) M. Hajjami, F. Ghorbani, F. Bakhti, Appl. Catal., A 2014, 470, 303-310. [23] a) L. B. Clapp, J. Chem. Educ. 1943, 20, 189-191; b) R. Sass, Acta Crystallogr. 1960, 13, 320-324. [24] M. A. Harmer, Q. Sun, M. J. Michalczyk, Z. Yang, Chem. Commun. 1997, 1803-1804. [25] D. Zuo, J. Lane, D. Culy, M. Schultz, A. Pullar, M. Waxman, Appl. Catal., B 2013, 129, 342-350. [26] M. Alvaro, A. Corma, D. Das, V. Fornés, H. García, J. Catal. 2005, 231, 48-55. [27] M. Bols, T. Skrydstrup, Chem. Rev. 1995, 95, 1253-1277. [28] M. Alvaro, A. Corma, D. Das, V. Fornes, H. Garcia, Chem. Commun. 2004, 956-957. [29] a) F. de Clippel, M. Dusselier, S. Van de Vyver, L. Peng, P. A. Jacobs, B. F. Sels, Green Chem. 2013, 15, 1398-1430; b) E. L. Margelefsky, R. K. Zeidan, V. Dufaud, M. E. Davis, J. Am. Chem. Soc. 2007, 129, 13691-13697. [30] a) Z.-M. Li, Y. Zhou, D.-J. Tao, W. Huang, X.-S. Chen, Z. Yang, RSC Adv. 2014, 4, 12160-12167; b) D.-J. Tao, J. Wu, Z.-Z. Wang, Z.-H. Lu, Z. Yang, X.-S. Chen, RSC Adv. 2014, 4, 1-7. [31] a) S. Habib, P. Salamé, F. Launay, V. Semmer-Herledan, O. arie, W. Zhao, N. Novak Tušar, A. Gédéon, J. Mol. Catal. A: Chem. 2007, 271, 117-125; b) W. Xie, C. Qi, H. Wang, Y. Liu, Fuel Process. Technol. 2014, 119, 98-104; c) G. Morales, L. F. Bautista, J. A. Melero, J. Iglesias, R. Sánchez- Vázquez, Bioresour. Technol. 2011, 102, 9571-9578; d) J. A. Melero, G. Vicente, M. Paniagua, G. Morales, P. Muñoz, Bioresour. Technol. 2012, 103, 142-151; e) R. Chakraborty, A. K. Gupta, R. Chowdhury, Renewable Sustainable Energy Rev. 2014, 29, 120-134; f) A. Drelinkiewicz, Z. Kalemba- Jaje, E. Lalik, R. Kosydar, Fuel 2014, 116, 760-771; g) G. Morales, R. van Grieken, A. Martín, F. Martínez, Chem. Eng. J. 2010, 161, 388-396; h) J. A. Melero, L. F. Bautista, G. Morales, J. Iglesias, R. Sánchez-Vázquez, Chem. Eng. J. 2010, 161, 323-331; i) S. Parambadath, M. Chidambaram, A. P. Singh, Catal. Today 2004, 97, 233-240; j) I. Agirrezabal-Telleria, J. Requies, M. B. Güemez, P. L. Arias, Appl. Catal., B 2014, 145, 34-42. [32] X. Wang, S. Cheng, J. C. C. Chan, J. C. H. Chao, Microporous Mesoporous Mater. 2006, 96, 321-330. [33] a) M. I. López, D. Esquivel, C. Jiménez-Sanchidrián, F. J. Romero-Salguero, ChemCatChem 2013, 5, 1002-1010; b) J. Alauzun, A. Mehdi, C. Reyé, R. J. P. Corriu, J. Am. Chem. Soc. 2006, 128, 8718-8719. [34] J. Taghavimoghaddam, G. P. Knowles, A. L. Chaffee, J. Mol. Catal. A: Chem. 2012, 358, 79-88. [35] a) P. Krawiec, E. Kockrick, L. Borchardt, D. Geiger, A. Corma, S. Kaskel, J. Phys. Chem. C 2009, 113, 7755-7761; b) D. Zareyee, M. Serehneh, J. Mol. Catal. A: Chem. 2014, 391, 88-91. [36] B. Lindlar, M. Lüchinger, M. Haouas, A. Kogelbauer, R. Prins in Studies in Surface Science and Catalysis, Vol. 135 (Eds.: F. F. F. D. R. A. Galarneau, J. Vedrine), Elsevier, 2001, pp. 318. [37] a) T.-Y. Ma, L. Liu, Z.-Y. Yuan, Chem. Soc. Rev. 2013, 42, 3977-4003; b) C. Matei Ghimbeu, L. Vidal, L. Delmotte, J.-M. Le Meins, C. Vix-Guterl, Green Chem. 2014, 16, 3079-3088; c) J. Li, J. Qi, C. Liu, L. Zhou, H. Song, C. Yu, J. Shen, X. Sun, L. Wang, J. Mater. Chem. A 2014, 2, 4144-4149. [38] a) R. Xing, Y. Liu, Y. Wang, L. Chen, H. Wu, Y. Jiang, M. He, P. Wu, Microporous Mesoporous Mater. 2007, 105, 41-48; b) L. Peng, A. Philippaerts, X. Ke, J. Van Noyen, F. De Clippel, G. Van Tendeloo, P. A. Jacobs, B. F. Sels, Catal. Today 2010, 150, 140-146; c) B. Chang, J. Fu, Y. Tian, X. Dong, RSC Adv. 2013, 3, 1987-1994; d) K. Nakajima, M. Okamura, J. N. Kondo, K. Domen, T. Tatsumi, S. Hayashi, M. Hara, Chem. Mater. 2008, 21, 186-193. [39] J. Janaun, N. Ellis, Appl. Catal., A 2011, 394, 25-31. [40] J. Pang, A. Wang, M. Zheng, T. Zhang, Chem. Commun. 2010, 46, 6935-6937. [41] a) X. Wang, R. Liu, M. M. Waje, Z. Chen, Y. Yan, K. N. Bozhilov, P. Feng, Chem. Mater. 2007, 19, 2395-2397; b) R. Liu, X. Wang, X. Zhao, P. Feng, Carbon 2008, 46, 1664-1669. [42] Z.-P. Sun, X.-G. Zhang, H. Tong, Y.-Y. Liang, H.-L. Li, J. Colloid Interface Sci. 2009, 337, 614-618. [43] a) D. Zareyee, M. Ghandali, M. Khalilzadeh, Catal. Lett. 2011, 141, 1521-1525; b) H. Alinghad, M. Zare, J. Chil. Chem. Soc. 2013, 58, 1840-1841. [44] a) C. Liang, K. Hong, G. A. Guiochon, J. W. Mays, S. Dai, Angew. Chem. Int. Ed. 2004, 43, 5785-5789; b) C. Liang, S. Dai, J. Am. Chem. Soc. 2006, 128, 5316-5317. [45] S. Tanaka, N. Nishiyama, Y. Egashira, K. Ueyama, Chem. Commun. 2005, 2125-2127.

This article is protected by copyright. All rights reserved [46] a) Y. Meng, D. Gu, F. Zhang, Y. Shi, H. Yang, Z. Li, C. Yu, B. Tu, D. Zhao, Angew. Chem. Int. Ed. 2005, 44, 7053-7059; b) F. Zhang, Y. Meng, D. Gu, Yan, C. Yu, B. Tu, D. Zhao, J. Am. Chem. Soc. 2005, 127, 13508-13509. [47] K. Hou, A. Zhang, L. Gu, M. Liu, X. Guo, J. Colloid Interface Sci. 2012, 377, 18-26. [48] S. Suganuma, K. Nakajima, M. Kitano, H. Kato, A. Tamura, H. Kondo, S. Yanagawa, S. Hayashi, M. Hara, Microporous Mesoporous Mater. 2011, 143, 443-450. [49] G.-P. Hao, W.-C. Li, S. Wang, G.-H. Wang, L. Qi, A.-H. Lu, Carbon 2011, 49, 3762-3772. [50] a) A. Sachse, A. Galarneau, F. Fajula, F. Di Renzo, P. Creux, B. Coq, Microporous Mesoporous Mater. 2011, 140, 58-68; b) A. Sachse, R. Ameloot, B. Coq, F. Fajula, B. Coasne, D. D. Vos, A. Galarneau, Chem. Commun. 2012, 48, 4749-4751; c) A. Sachse, A. Galarneau, B. Coq, F. Fajula, New J. Chem. 2011, 35, 259-264; d) A. Sachse, A. Galarneau, F. Di Renzo, F. Fajula, B. Coq, Chem. Mater. 2010, 22, 4123-4125. [51] a) H. Nishihara, S. Iwamura, T. Kyotani, J. Mater. Chem. 2008, 18, 3662-3670; b) F. Svec, J. M. J. Fréchet, Science 1996, 273, 205-211; c) Z. Sun, Y. Deng, J. Wei, D. Gu, B. Tu, D. Zhao, Chem. Mater. 2011, 23, 2176-2184. [52] K. Murakami, Y. Satoh, I. Ogino, S. R. Mukai, Ind. Eng. Chem. Res. 2013, 52, 15372-15376. [53] a) D. Wu, F. Xu, B. Sun, R. Fu, H. He, K. Matyjaszewski, Chem. Rev. 2012, 112, 3959-4015; b) W. Lu, Z. Wei, D. Yuan, J. Tian, S. Fordham, H.-C. Zhou, Chem. Mater. 2014, 26, 4589-4597; c) Q. Chen, D.- P. Liu, J.-H. Zhu, B.-H. Han, Macromolecules 2014, 47, 5926-5931; d) F. M. Wisser, K. Eckhardt, D. Wisser, W. Böhlmann, J. Grothe, E. Brunner, S. Kaskel, Macromolecules 2014, 47, 4210-4216; e) R. J. Kalbasi, M. Negahdari, J. Mol. Struct. 2014, 1063, 259-268; f) J. Wang, S. Xu, Y. Wang, R. Cai, C. Lv, W. Qiao, D. Long, L. Ling, RSC Adv. 2014, 4, 16224-16232. [54] a) S. Wan, J. Guo, J. Kim, H. Ihee, D. Jiang, Angew. Chem. Int. Ed. 2009, 48, 5439-5442; b) P. Kuhn, M. Antonietti, A. Thomas, Angew. Chem. Int. Ed. 2008, 47, 3450-3453. [55] D. Zhang, Y. Hao, L. Zheng, Y. Ma, H. Feng, H. Luo, J. Mater. Chem. A 2013, 1, 7584-7591. [56] D.-H. Choi, R. Ryoo, J. Mater. Chem. 2010, 20, 5544-5550. [57] F. Liu, S. Zuo, W. Kong, C. Qi, Green Chem. 2012, 14, 1342-1349. [58] a) L. Zhang, S. Wu, C. Li, Q. Yang, Chem. Commun. 2012, 48, 4190-4192; b) X. Zhang, Y. Zhao, J. Peng, Q. Yang, Green Chem. 2015, 17, 1899-1906. [59] W. Wang, X. Zhuang, Q. Zhao, Y. Wan, J. Mater. Chem. 2012, 22, 15874-15886. [60] X. Zhang, L. Zhang, Q. Yang, J. Mater. Chem. A 2014, 2, 7546-7554. [61] M. Choi, F. Kleitz, D. Liu, H. Y. Lee, W.-S. Ahn, R. Ryoo, J. Am. Chem. Soc. 2005, 127, 1924-1932. [62] F. Liu, W. Kong, C. Qi, L. Zhu, F.-S. Xiao, ACS Catalysis 2012, 2, 565-572. [63] Q. Yue, M. Wang, J. Wei, Y. Deng, T. Liu, R. Che, B. Tu, D. Zhao, Angew. Chem. Int. Ed. 2012, 51, 10368-10372. [64] D. Nandan, P. Sreenivasulu, S. K. Saxena, N. Viswanadham, Chem. Commun. 2011, 47, 11537-11539. [65] B. Chang, Y. Tian, W. Shi, J. Liu, F. Xi, X. Dong, RSC Adv. 2013, 3, 20999-21006. [66] a) C. Pirez, A. F. Lee, C. Jones, K. Wilson, Catal. Today 2014, 234, 167-173; b) I. K. Mbaraka, B. H. Shanks, J. Catal. 2005, 229, 365-373. [67] a) B. Karimi, D. Zareyee, J. Mater. Chem. 2009, 19, 8665-8670; b) B. Karimi, A. Mobaraki, H. M. Mirzaei, D. Zareyee, H. Vali, ChemCatChem 2014, 6, 212-219; c) F.-Y. Yeoh, A. Matsumoto, T. Baba, J. Porous Mater. 2009, 16, 283-289. [68] S. Inagaki, S. Guan, T. Ohsuna, O. Terasaki, Nature 2002, 416, 304-307. [69] Q. Yang, M. P. Kapoor, S. Inagaki, J. Am. Chem. Soc. 2002, 124, 9694-9695. [70] P. Dhepe, M. Ohashi, S. Inagaki, M. Ichikawa, A. Fukuoka, Catal. Lett. 2005, 102, 163-169. [71] A. Karam, J. C. Alonso, T. I. Gerganova, P. Ferreira, N. Bion, J. Barrault, F. Jerome, Chem. Commun. 2009, 7000-7002. [72] E.-B. Cho, D. Kim, J. Phys. Chem. Solids 2008, 69, 1142-1146. [73] H.-Y. Wu, C.-T. Chen, I. M. Hung, C.-H. Liao, S. Vetrivel, H.-M. Kao, J. Phys. Chem. C 2010, 114, 7021-7029. [74] M. P. Kapoor, M. Yanagi, Y. Kasama, T. Yokoyama, S. Inagaki, T. Shimada, H. Nanbu, L. R. Juneja, J. Mater. Chem. 2006, 16, 3305-3311. [75] D. Esquivel, C. Jimenez-Sanchidrian, F. J. Romero-Salguero, J. Mater. Chem. 2011, 21, 724-733. [76] M. Karaki, A. Karout, J. Toufaily, F. Rataboul, N. Essayem, B. Lebeau, J. Catal. 2013, 305, 204-216.

This article is protected by copyright. All rights reserved [77] A. Karam, J. C. Alonso, T. I. Gerganova, P. Ferreira, N. Bion, J. Barrault, F. Jérôme, Chem. Commun. 2009, 7000-7002. [78] C. Bispo, K. De Oliveira Vigier, M. Sardo, N. Bion, L. Mafra, P. Ferreira, F. Jerome, Catal. Sci. Technol. 2014, 4, 2235-2240. [79] C. Li, J. Yang, X. Shi, J. Liu, Q. Yang, Microporous Mesoporous Mater. 2007, 98, 220-226. [80] S. Hamoudi, S. Kaliaguine, Microporous Mesoporous Mater. 2003, 59, 195-204. [81] S. Shylesh, A. Wagener, A. Seifert, S. Ernst, W. R. Thiel, Angew. Chem. Int. Ed. 2010, 49, 184-187. [82] L. Saikia, D. Srinivas, P. Ratnasamy, Appl. Catal., A 2006, 309, 144-154. [83] F. Zhang, C. Liang, M. Chen, H. Guo, H. Jiang, H. Li, Green Chem. 2013, 15, 2865-2871. [84] M. P. Kapoor, Q. Yang, S. Inagaki, J. Am. Chem. Soc. 2002, 124, 15176-15177. [85] M. P. Kapoor, W. Fujii, Y. Kasama, M. Yanagi, H. Nanbu, L. R. Juneja, J. Mater. Chem. 2008, 18, 4683-4691. [86] a) B. Karimi, D. Elhamifar, O. Yari, M. Khorasani, H. Vali, J. H. Clark, A. J. Hunt, Chem. Eur. J. 2012, 18, 13520-13530; b) B. Karimi, D. Elhamifar, J. H. Clark, A. J. Hunt, Chem. Eur. J. 2010, 16, 8047- 8053. [87] D. Elhamifar, B. Karimi, A. Moradi, J. Rastegar, ChemPlusChem 2014, 79, 1147-1152. [88] D. Elhamifar, M. Nasr-Esfahani, B. Karimi, R. Moshkelgosha, A. Shábani, ChemCatChem 2014, 6, 2593-2599. [89] M. Sharifi, J. Schneider, M. Wark, Microporous Mesoporous Mater. 2012, 151, 506-510. [90] M. Jaroniec, Nature 2006, 442, 638-640. [91] M. Park, S. Park, M. Selvaraj, I. Kim, C.-S. Ha, J. Porous Mater. 2011, 18, 217-223. [92] C. Li, J. Liu, L. Zhang, J. Yang, Q. Yang, Microporous Mesoporous Mater. 2008, 113, 333-342. [93] M. Sasidharan, A. Bhaumik, ACS Appl. Mater. Interfaces 2013, 5, 2618-2625. [94] K. Nakajima, I. Tomita, M. Hara, S. Hayashi, K. Domen, J. N. Kondo, Catal. Today 2006, 116, 151- 156. [95] D. Esquivel, E. De Canck, C. Jimenez-Sanchidrian, P. Van Der Voort, F. J. Romero-Salguero, J. Mater. Chem. 2011, 21, 10990-10998. [96] F.-X. Zhu, W. Wang, H.-X. Li, J. Am. Chem. Soc. 2011, 133, 11632-11640.