Supporting Information

SUPPORTING INFORMATION

Adsorptive characterization of the ZIF-68 Metal-Organic

Framework: a complex structure with amphiphilic properties.

Stijn Van der Perrea, Tom Van Asschea, Belgin Bozbiyika, Jeroen Lannoeyeb, Dirk. E. De

Vosb, Gino V. Barona, Joeri F.M. Denayera,1

a Vrije Universiteit Brussel, Department of Chemical Engineering, Brussel, Belgium. b Katholieke Universiteit Leuven, Centre of Surface Chemistry and Catalysis, Leuven,

Belgium.

1 Corresponding author: Joeri F.M. Denayer

E-mail: [email protected]

Tel.: +32 2 629 17 98

Fax: +32 2 629 32 48

Table of Contents

1. SEM pictures and determination of average crystal size S3

2. Ar isotherm S4

3. Adsorption isotherms S5

4. Fourier Transform Infrared Spectroscopy S11

5. Adsorption kinetics S14

6. Kinetic batch experiments S18

7. Stability of ZIF-68 S20

8. Structure ZIF-68 S23

9. Supporting Information References S26

1. SEM pictures and determination of average crystal size

The average crystal size of this ZIF-68 synthesis batch was calculated from a set of SEM pictures

(Scanning Electron Microscope) with measurement of about 100 different crystals (Figure S1). The size distribution is given in Figure S2, where the average crystal size is calculated on basis of the cumulative volume at 50 % (dav = 160 µm).

Figure S1. SEM picture of a ZIF-68 synthesis batch.

100

rav = 80 µm 60

cumulativevolume (%) 20

0 0 50 100 150 crystal radius (µm)

Figure S2. The particle size distribution of ZIF-68.

2. Argon porosimetry

Figure S3 shows the argon uptake on ZIF-68 at 87 K. Micropore volume was determined from the intercept of a standard t-plot [S1], assuming adsorbed argon to have the density of liquid argon (1.400 g/ml). About 23.6 mg of ZIF-68 powder was activated by gradually heating at 1 K/min to 523 K. The t-plot (Figure S4) is applied to relative pressures from 0.4 to 0.95 (12 points).

400

350

300

250

200

150

100 porevolume(cm³/g STP)

0 0.000001 0.00001 0.0001 0.001 0.01 0.1 1 P/Psat

Figure S3. Argon porosimetry on ZIF-68 at 87 K. Full symbols indicate the adsorption branch and open symbols the desorption branch of the isotherms.

450

400

350

300

250

200

150

100 porevolume(cm³/g STP) 50

0 0 2 4 6 8 10 12 14 16 18 Statistical thickness (Å)

Figure S4. t-plot of a ZIF-68 sample at 87 K. The intercept gives a t-plot micropore volume of 0.441 ml/g.

3. Vapor phase adsorption

a. Experimental method for vapor phase isotherms

Vapor phase adsorption isotherms were measured with the gravimetric method on a microbalance of

VTI Corporation (SGA-100H). A container, filled with a liquid adsorbate, is temperature controlled through Peltier elements. Nitrogen (N2) bubbling through the reservoir entrains the organic vapor. This

N2-organic vapor stream continuously flows over the sample positioned in a sample holder connected to the microbalance. The vapor pressure is controlled by regulating either the dilution rate or the saturator temperature. Low vapor pressures were obtained by diluting the saturator flow at the lowest saturator temperature with a flow of nitrogen gas. Due to rapid response of the dilution valves, the increase of vapor pressure with time at a change in partial pressure point can be approximated as a step function. This allows kinetic uptake data to be retrieved from the valve controlled isotherm point measurements. In this work, we cannot exclude the interference of film transfer resistance, internal surface barriers or bed diffusion.

About 10 mg of the adsorbent powder, without sample reuse, was placed in a stainless steel sample pan and positioned in the microbalance system. After activation by heating to 523 K at a heating rate of 1 K/min under N2 flow, adsorption isotherms of all adsorbates (except water) were determined at

323 K by weighing the adsorbate uptake at different partial pressures.

The water adsorption isotherm on ZIF-68 was measured on a SENSYS Evo TG/DSC device

(SETARAM Instrumentation), coupled with the Wetsys humidity generator. In the Wetsys device, a dry and a saturated gas flow are mixed within a mixing chamber. The humidity is measured with a

Rotronic humidity sensor (precision ±1.5 % RH) at the exit of the humidity generator. In this work, helium (He) was used as carrier gas. The relative humidity was varied between 5 % RH and 70.0 %

RH with steps at every 5 % RH. The humidified carrier gas flows through a heated transfer line into the TG/DSC measurement cell. About 11 mg of the adsorbent was added in the sample crucible. After activation by heating to 523 K at a heating rate of 1 K/min under He flow (50 ml/min), the water adsorption isotherm was determined at 303 K.

The number of adsorbate molecules per unit cell of the ZIF-68 adsorbent (q) was calculated with the following formula:

(S1)

23 where qsat is the saturation capacity (in mol/g), Na i Av g dr ’ n b r 6.02 x 10 ), and Nuc is the number of unit cells per gram dry ZIF-68 (8.52 x 1019 unit cells/g) [S2].

b. Adsorption isotherms

Figure S5a shows the adsorption isotherms, expressed in g/g, of the polar tested adsorbates in a linear scale. Methanol, ethanol and 1-propanol shows an explicit two-step uptake, which is clearly observed in the zoom-in plot. For acetone and MeCN, this two-step behavior is less explicit. In Figure S5b the isotherms of the larger alcohols are added and displayed in a logarithmic scale.

a) 0.30

0.25 0.25

0.20

0.15 0.15

q (g/g) q 0.10 q(g/g)

0.10 0.05

0.00 0.05 0 0.05 0.1 P/Psat

0.00 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 P/Psat

b) 0.30

0.25

0.20

0.15 q(g/g)

0.10

0.05

0.00 0.0001 0.001 0.01 0.1 1 P/Psat

Figure S5. (a) Adsorption isotherms of small (most polar) alcohols (in red); methanol (squares), ethanol (triangles) and 1- propanol (circles), and other polar components (in yellow); water (squares) acetone (triangles) and MeCN (in circles) at 323

K on ZIF-68 in linear scale. Water is measured at 303 K. (b) Added with adsorption isotherms of larger alcohols (blue); 1- butanol (triangles), 1-pentanol (circles) and 1-hexanol (squares) at 323 K on ZIF-68 in logarithmic scale.

Figure S6 and S7 show the isotherms of the aromatics and C6 alkanes, respectively.

0.40

0.35

0.30 benzene

0.25 toluene

0.20 o-xylene

q(g/g) p-xylene 0.15 m-xylene 0.10 1,3,5-TMB 0.05 1,3,5-TIPB 0.00 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 P/Psat Figure S6. Adsorption isotherm of the aromatic compounds at 323 K on ZIF-68 in non-logarithmic scale.

0.30

0.25

0.20

n-C6 0.15

2-MeC5 q(g/g) 0.10 2,3-diMeC4 2,2-diMeC4 0.05 cC6

0.00 0 0.1 0.2 0.3 0.4 0.5 0.6 P/Psat Figure S7. Adsorption isotherm of the C6 alkanes at 323 K on ZIF-68 in non-logarithmic scale.

A comparison between ZIF-8 and ZIF-68 for H2O, methanol and 1-hexanol is shown in Figure S8, indicating a less hydrophobic character for ZIF-68.

a) b)

Figure S8. (a) Methanol (rectangles) and 1-hexanol (circles) isotherms at 323 K and (b) H2O isotherms at 313 K (ZIF-8, data from [S3]) and 303 K (ZIF-68) of ZIF-68 (solid lines with closed symbols) and ZIF-8 (dotted lines with open symbols).

Table S1 shows the adsorption capacities (expressed in different units) for the whole set of tested adsorbates and the numerical values of the liquid density to convert gravimetric into volumetric uptake units for the various adsorbates. Those liquid densities were calculated via:

(S2) [ ( ⁄ ) ]

where is in mol/dm³ and is in K. The coefficients and are tabulated in [S4].

Table S1. Adsorption capacities of different adsorbates on ZIF-68 in vapor phase at 323 K, for water at 303 K and liquid densities at 323 K.

adsorbate dkin (Å) P/Psat (-) q (g/g) q (ml/g) q (molec/UC) ρliq (g/ml) methanol 3.8 0.71 0.284 0.365 62.6 0.777 ethanol 4.3 0.48 0.270 0.354 41.4 0.762

1-propanol 4.7 0.51 0.271 0.348 31.9 0.777

1-butanol 5.0 0.50 0.266 0.340 25.4 0.783

1-pentanola 5.0 0.48 0.263 0.331 21.1 0.793

1-hexanola 5.0 0.45 0.254 0.318 17.6 0.798 acetone 4.7 0.59 0.288 0.380 35.0 0.757 acetonitrile (MeCN) 3.4 0.59 0.291 0.389 50.2 0.750 n-hexane 4.3 0.57 0.241 0.381 19.8 0.633 cyclohexane 6.0 0.58 0.294 0.392 24.7 0.750

2-methylpentane 5.0 0.51 0.253 0.406 20.8 0.624

2,3-dimethylbutane 5.6 0.55 0.272 0.430 22.3 0.633

2,2-dimethylbutane 6.2 0.55 0.248 0.396 20.3 0.626 benzene 5.9 0.58 0.306 0.362 27.7 0.846 toluene 6.1 0.64 0.329 0.391 25.2 0.840 p-xylene 6.7 0.66 0.327 0.392 21.8 0.834 m-xylene 7.1 0.56 0.337 0.402 22.4 0.838 o-xylene 7.4 0.57 0.355 0.415 23.7 0.855

1,3,5-trimethylbenzene 7.5 0.57 0.302 0.352 17.8 0.859

1,3,5-triisopropylbenzene 8.5 0.44 0.219 0.261 7.6 0.840 waterb 2.7 0.70 0.028 0.028 11.0 0.992 a The kinetic diameter of 1-pentanol and 1-hexanol is assumed to be identical to 1-butanol (in analogy with the linear alkanes, where n-pentane and n-hexane have the same kinetic diameter as n-butane [S5]). b Only for water no real saturation capacity is obtained.

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4. Fourier Transform Infrared Spectroscopy

FTIR was used for the investigation of the specific interactions on the ZIF-linkers of the adsorbent.

FTIR measurements were performed with a Thermo Scientific Nicolet 6700 FTIR Spectrometer with a diamond crystal single bounce attenuated total reflectance (ATR) setup. The diamond crystal has a circular surface of 1.5 mm diameter in which the measured area was exposed. The spectra were acquired between 600 and 4000 cm-1 with an accumulation of 32 scans and a resolution of 4 cm-1.

Spectra acquisition was controlled by the OMNIC 8.1 software package (Thermo Electron

Corporation, Madison, WI). The ZIF-68 sample was activated via the normal procedure. The other samples were activated in the same conditions, and then immersed in adsorbate (methanol, n-hexane or benzene). Excess adsorbate was evaporated under N2 atmosphere. Also a blank measurement of the abovementioned adsorbates was recorded and subtracted from the spectra of the ZIF-68 samples with adsorbate.

Figure S9 shows the different IR spectra of the activated ZIF-68 and of the adsorbed ZIF-68 samples

(methanol, n-hexane and benzene). The effects of hydrogen bonding on infrared bands of the nitro acceptor near 1550 (asymmetric vibration) and 1350 cm-1 (symmetric vibration) were examined

(surrounded by dashed lines in Figure S9). It was found that the symmetric and asymmetric O–N–O stretching vibrations of the nitro group were both shifted to lower frequencies, and this was more pronounced in the case of methanol (Figures S10, S11 and Table S2). The relatively large shifts for benzene can be attributed to nitro-π king in r i n [S6, S7]. Also small shifts were observed in the absorption band around 1500 cm-1 (typical for C=C bonds in aromatic rings), which can point to

p ifi π-π r XH-π wi h X O, interactions via benzyl groups of the bIM linkers. Shifts of ± 1 cm-1 are not significant. Normally, hydrogen bonding also broadens intensity, which is clearly observed for methanol.

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Figure S9. Infrared spectra (represented in % transmittance mode) of activated ZIF-68 (red) and ZIF-68 with n-hexane

(purple), benzene (blue) and methanol (green). *denotes a shift around the band at 1500 cm-1 (typical for aromatic C=C bond) for the tested probe molecules. The bands of the nitro groups are enclosed by the dashed lines around 1350 and 1550 cm-1.

Figure S10. νs(NO) band of activated ZIF-68 (red) and ZIF-68 with n-hexane (purple), benzene (blue) and methanol (green).

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Figure S11. νas(NO) band of activated ZIF-68 (red) and ZIF-68 with n-hexane (purple), benzene (blue) and methanol (green).

Table S2. Vibrational frequencies (cm-1) for the different samples.

act. ZIF-68 ZIF-68 + nC6 ZIF-68 + C6H6 ZIF-68 + MeOH

Nitro

νs (N-O) 1369.70 1363.61 1361.18 1361.50

νas (N-O) 1541.31 1538.43 1537.47 1536.99 1533.61

Aromatic C=C 1504.60 1499.48 1496.25 1496.81

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5. Adsorption kinetics

The intracrystalline diff i n d w d riv d fr Fi k’ nd w f diff i n. It is assumed that adsorbent crystals are spherical and the intracrystalline diffusion coefficient is constant.

Extraction of the Fick diffusion coefficients was done by fitting the experimental results (qaverage versus time) with the following equations according to an isothermal model [S8]:

( ) (S3)

∫ ( ) (S4)

with ( ) the concentration of the adsorbed phase.

The equation was solved with the approximation that the effect of the external concentration change due to adsorption was negligible, such that the next initial and boundary conditions could be used:

( ) ( ) ( )

Here is the crystal radius, and are the initial and final (equilibrium) adsorbed capacity.

Due to the non-uniformity of the crystal sizes in the samples used in this study, the ZIF-68 particle size distribution was taken into account for accurate determination of the diffusivity [S9]:

∑ (S5)

where is the Fick diffusion coefficient for crystals with radius and is the volume fraction of crystals with radius .

Since is still loading-dependent, the thermodynamically corrected apparent diffusion coefficient was calculated according to:

(S6)

S14 where ⁄ represents the thermodynamic factor.

From data fitting of the Langmuir-Sips isotherm for methanol, ethanol and 1-propanol (adsorbates which do not display type I isotherm), the model parameters of the fitted isotherm are determined and shown in Table S3. The remaining adsorbates are fitted with simple Langmuir models. The fitting of these parameters is necessary to calculate the thermodynamic factor in an analytical way.

Ruthven’s criterion was used to assess if heat effects associated with adsorption could be neglected, meaning that the assumption of isothermal adsorption is valid [S10]:

(S7)

( ) ( ) ( ) (for Langmuirian system) (S8)

with = heat transfer coefficient (W m-2 K-1)

= specific external surface area: (m-1)

-3 -1 = specific volumetric heat capacity (J m K )

-1 ∑ = average crystal diameter (m ): ∑ 85.7 µm ∑

= intracrystalline diffusivity (m2 s-1)

= adsorption enthalpy (J mol-1)

-3 = saturation uptake in Langmuir isotherm expression (mol m )

R = gas constant (J mol-1 K-1)

= fractional uptake of adsorbent: ⁄

If either is large (heat transfer much faster than internal diffusion) or → 0 (high heat capacity or low heat of adsorption) the intrusion of heat transfer resistance will be insignificant. So thermal resistance can be neglected if either < 0.01 or ⁄( ) > 100 [S10].

S15

With the purpose to approach the limit of isothermal behavior, the calculation is performed for an adsorbate with high diffusivity (highest Fick diffusion constant) and for an adsorbate with high adsorption enthalpy: benzene and MeCN, respectively (both displaying Langmuir behavior). A couple of assumptions were taken into account to calculate parameters and :

1. As adsorption enthalpy, the enthalpy at zero loading ΔH0 was used.

2. Since the specific volumetric heat capacity of ZIF-68 is unknown, the heat capacity of ZIF-8

(h = 2.09 J g-1 K-1 [S11]), with same metal ions and (similar) imidazole linkers, was chosen

and corrected with the density of ZIF-68 (ρ = 1.047 g cm-3 [S12]). Different tested MOFs have

heat capacities of the same order [S11, S13].

3. For the heat transfer coefficient, a value of 10 W m-2 K-1 was proposed (minimal value for air)

Both adsorbates fulfill the criterion of ⁄( ) > 100, concluding we can neglect the heat effects and can use the isothermal model:

For benzene: = 256 and = 0.296 for = 4.59 10-12 m2 s-1 and = 0.94

For MeCN: = 1423 and = 2.90 for = 8.26 10-13 m2 s-1 and = 0.70

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Table S3. Fitted isotherm model parameters for all tested adsorbates.

-1 -n adsorbate qsat,1 (g/g) K1 (Pa ) qsat,2 (g/g) K2 (Pa ) n methanol 0.070 (± 0.012) 26.76 (± 7.52) 0.216 (± 0.008) 1039 (± 1230) 4.81 (± 0.79) ethanol 0.184 (± 0.007) 29.13 (± 0.96) 0.093 (± 0.002) 1.38 1011 9.74 (± 0.08)

1-propanol 0.217 (± 0.025) 64.94 (± 2.83) 0.065 (± 0.002) 2.28 1013 8.66 (± 0.11)

1-butanol 0.252 (± 0.008) 598.2 (± 115.5) - - -

1-pentanol 0.251 (± 0.005) 1176 (± 188) - - -

1-hexanol 0.248 (± 0.006) 1076 (± 168) - - - acetonea 0.290 (± 0.002) 117.3 (± 6.2) - - - acetonitrilea 0.311 (±0.005) 27.17 (± 1.69) - - - n-hexane 0.238 (± 0.002) 413.2 (± 63.2) - - - cyclohexane 0.300 (± 0.002) 74.61 (± 11.36) - - -

2-methylpentane 0.249 (± 0.003) 421.1 (± 74.2) - - -

2,3-dimethylbutane 0.267 (± 0.004) 290.6 (± 62.8) - - -

2,2-dimethylbutane 0.247 (±0.001) 532.6 (± 69.6) - - - benzene 0.300 (± 0.003) 302.1 (± 49.5) - - - toluene 0.320 (± 0.003) 500.0 (± 63.1) - - - p-xylene 0.316 (± 0.006) 255.7 (± 69.2) - - - m-xylene 0.324 (± 0.007) 381.7 (± 77.5) - - - o-xylene 0.348 (± 0.004) 374.7 (± 47.2) - - -

1,3,5-TMB 0.290 (± 0.006) 504.6 (± 109.5) - - -

1,3,5-TIPB 0.220 (± 0.003) 206.8 (± 98.8) - - - a Although, acetone and MeCN display S-shaped isotherms (Figure 4b), these components were approximated by Langmuir type isotherms.

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6. Kinetic batch experiments

a. Experimental method

Ethanol and 1-butanol were bought from Sigma Aldrich as ACS reagent grade. Water was used as solvent, wherein the alcohols were dissolved, each with a concentration of 0.5 wt%. The uptake measurements were carried out in VWR borosilicate 3.3 glass vials of 50 ml. About 0.7 g adsorbent, in powder form, was added to the vials and activated in a ventilated oven at 1 K/min to 523 K during 6h.

Then the vial with the activated adsorbent was cooled to room temperature under N2 atmosphere and filled with a water / alcohol solution (total volume of ca. 56 ml), sealed with a polypropylene (PP) cap

(VWR International LLC, USA) combined with a Versilic® silicone stop (Saint-Gobain, France) and stirred at 360 rpm. The uptake curves were obtained by analyzing liquid samples (ca. 0.8 g each sample) for their alcohol concentration via GC-analysis (Agilent 6890 System, FID detector, HP-5 column). This procedure was followed for pure compounds (ethanol and 1-butanol with a concentration of 0.5 wt%) diluted in water and for an alcohol mixture (50/50 ethanol/1-butanol) (with a total concentration of about 1 wt%) diluted in water, all at room temperature.

b. Calculation method

The following equation, derived from the total and component mass balance, was used to calculate the amount adsorbed during each time interval ( , ) between two sampling events:

( ) ( ∑ ∑ ) (S9) ( )

with

: amount adsorbing between time and

: fraction of component i at time

: initial total mass of fluid

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: initial adsorbent mass

∑ : total amount adsorbed phase at time

: fraction of liquid phase in the system

∑ : total amount of sample removed from the system at time

The equation incorporates the change of total mass of the system and the change of concentration of the fluid due to adsorption (full elaborated explanation in Supporting Information of [S14] by Cousin

Saint Remi et al.). By summing up for each time interval, the total amount adsorbed is determined in function of time, generating the uptake curves.

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7. Stability of ZIF-68

After immersion in water (during kinetic batch experiments), a clear decrease (± 30 %) in pore volume of the adsorbent is observed via Ar porosimetry (Figure S12). The hysteresis can be ascribed to decomposition of the structure. However, no significant differences are observed in the XRD profiles

(Figure S13). Based on these XRD patterns, no degradation in pore volume could be expected. The sample is regenerated by evaporating the remaining liquid (bulk water with still very small amounts of ethanol and/or 1-butanol) at a maximum temperature of 363 K with a heating rate of 0.1 K/min. This temperature was kept there for several days (2-3 days). Afterwards, the physically dried sample was further regenerated by heating it to 523 K at a rate of 1K/min during 6 hours.

450

400

350

300

250

200

150

porevolume(ml/g STP) 100

0 0.000001 0.00001 0.0001 0.001 0.01 0.1 1 P/Psat

Figure S12 Ar porosimetry on ZIF-68 samples at 87 K before (blue) and after (green) water-alcohol experiments. Full symbols indicate the adsorption branch and open symbols the desorption branch of the isotherms.

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after water experiment Intensity(a.u.) MeOH exchanged

simulated

5 15 25 35 45 55 2θ (°) Figure S13 The X-ray diffraction (XRD) patterns of a simulated ZIF-68 (red), and a sample before (blue) and after (green) a water-alcohol experiment (immersion in water).

The significant decrease in pore volume can be ascribed to a change in the pore structure of ZIF-68

(by collapsing of the cages) or to partial blocking of certain pores/channels. A simulation of the pore size distribution via a Density Functional Theory (DFT) calculation, based on the Ar isotherms (at 87

K), was performed, assuming cylindrical pores (Figure S14). Although, parameters of a non-local DFT

(NLDFT) for zeolites/silica (Ar at 87 K) were used in the calculation model (with cylindrical pores), a very good fitting between the measured and fitted values was observed, with a fitting error of 0.109 %.

A remarkable decrease in pore volume within this pore size region is observed.

1.2

1.0

0.8

0.6

0.4 dV(r)(cm³/Å/g) 0.2

0.0 0 2 4 6 8 10 Half pore width (Å) Figure S14. DFT pore size distribution of two samples of ZIF-68, before (blue) and after (green) liquid water contact at room temperature.

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A small, extra experiment was performed to test the stability of the MOF in the presence of humid conditions at a certain level of relative humidity, which differentiates from stability tests in liquid water. First, an isotherm of n-hexane was measured before the exposure of water vapor. Subsequently, the sample was regenerated and contacted with water vapor at different relative humidities for almost

20 hours (with max. RH of 90 %) at 323 K. Afterwards, the sample was activated at the normal regeneration procedure (1 K/min to 523 K). Then, again an adsorption isotherm of n-hexane was recorded to compare its capacity before and after. A negligible decrease (~ 2%) of the adsorption capacity is observed (Figure S15), concluding ZIF-68 is resistant against high humidities, which opens perspectives in the adsorption of VOCs in air.

0.25

0.20

0.15

q(g/g) 0.10

0.05

0.00 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 P/Psat

Figure S15. Adsorption isotherms of n-hexane at 323 K b f r ♦ nd f r ● xp r w r v p r (with a maximum relative humidity of 90 %).

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8. Structure of ZIF-68

A schematic representation of the cage structure of ZIF-68 (front (a) and side (b) view) is shown in

Figure S16. The HPR (gray) and GME (purple) cages are alternated in the small channel, while the

KNO (blue) cages are only found in the large channel. A small channel is surrounded by three small and three large channels. A more detailed view of each cage is shown in the next figures (Figures S17,

S18 and S19).

Figure S16. Schematic representation of the cage structure of ZIF-68: (a) front view (looking down the c-axis) and (b) side view (looking down the a-axis). Solid white lines denote the boundaries of one unit cell. The cages are shaped by connecting the adjacent Zn atoms, creating polyhedrons. Therefore, only Zn atoms are showed (carbon, hydrogen, nitrogen and oxygen are omitted for clarity). The three different colors are assigned to the three types of cages: HPR (gray), GME (purple) and

KNO (blue).

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Figure S17. A detailed side view of the HPR cage (shaped by connecting the adjacent Zn atoms): a closed (left) and an open

(right) polyhedron.

Figure S18. A detailed view on the GME cage (shaped by connecting the adjacent Zn atoms): (top) front view (closed polyhedron), side view of a closed (left) and an open (right) polyhedron.

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Figure S19. A detailed view on the KNO cage (shaped by connecting the adjacent Zn atoms): (top) front view with central projection, side view of a closed (left) and an open (right) polyhedron.

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9. Supporting Information References

[S1] J.H. de Boer, B.C. Lippens, B.G. Linsen, J.C.P. Broekhoff, A. van den Heuvel, T.J. Osinga, J.

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[S2] R.B. Rankin, J. Liu, A.D. Kulkarni, J.K. Johnson, J. Phys. Chem. C, 113 (2009) 16906-16914.

[S3] J.C. Saint Remi, T. Remy, V. Van Hunskerken, S. Van der Perre, T. Duerinck, M. Maes, D. De

Vos, E. Gobechiya, C.E.A. Kirschhock, G.V. Baron, J.F.M. Denayer, Chemsuschem, 4 (2011) 1074-

1077.

[S4] D.W. Green, R.H. Perry, Perry's Chemical Engineers' Handbook McGraw-Hill, New York, 2007, pp. 2640

[S5] R.W. Broach, Zeolite Types and Structures, Zeolites in Industrial Separation and Catalysis,

Wiley-VCH Verlag GmbH & Co. KGaA2010, pp. 27-59.

[S6] B.R. Kaafarani, B. Wex, A.G. Oliver, J.A. Krause Bauer, D.C. Neckers, Acta Crystallogr. Sect.

E, 59 (2003) o227-o229.

[S7] S. Morita, A. Fujii, N. Mikami, S. Tsuzuki, J. Phys. Chem. A, 110 (2006) 10583-10590.

[S8] D.M. Ruthven, Principles of adsorption and adsorption processes, Wiley, New York u.a, 1984.

[S9] C. Zhang, R.P. Lively, K. Zhang, J.R. Johnson, O. Karvan, W.J. Koros, J. Phys. Chem. Lett., 3

(2012) 2130-2134.

[S10] D.M.R.a.D.N.T. Jörg Kärger, Diffusion in Nanoporous Materials. , WILEY-VCH Verlag2012.

[S11] Z. Hu, L. Zhang, J. Jiang, J. Chem. Phys., 136 (2012) -.

[S12] R. Banerjee, A. Phan, B. Wang, C. Knobler, H. Furukawa, M. O'Keeffe, O.M. Yaghi, Science,

319 (2008) 939-943.

[S13] C.-H. Jiang, L.-F. Song, C.-L. Jiao, J. Zhang, L.-X. Sun, F. Xu, H.-Z. Zhang, Q.-Y. Xu, Z.

Gabelica, J. Therm. Anal. Calorim., 103 (2011) 1095-1103.

[S14] J. Cousin Saint Remi, G.V. Baron, J.F.M. Denayer, J. Phys. Chem. C, 117 (2013) 9758-9765.

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