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 1,6 7 8 2,8,9 1 Yoshio Bando, Kevin C.-W. Wu, Jeonghun Kim, Yusuke Yamauchi * and Yusuke Ide * 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 1 This article is protected by copyright. All rights reserved Abstract 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 2 This article is protected by copyright. All rights reserved 1. Introduction 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 3 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. 4 This article is protected by copyright. All rights reserved 2. Precursors for Sulfonation 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]