Acidic OH Groups Research Articles

Intramolecular H/D Exchange of Ethanol Catalyzed by Acidic OH Groups on H-ZSM-5 Zeolite

IR observation of ethanol adsorption clarified the presence of the apparent intramolecular isotope exchange from CD3CH2OH to CHD2CH2OD on acidic OH groups of H-ZSM-5 zeolite. This reaction did not proceed with CD3OH nor CH3CD2OH, implying that the β-hydrogen of alcohol had interaction with the lattice oxygen adjacent to Al and that the reaction was mediated by isotope exchange of CD3 groups of ethanol and OH groups on zeolite.

Near-infrared laser-induced generation of three rare conformers of glycolic acid.

Structural transformations were induced in conformers of glycolic acid by selective excitation with monochromatic tunable near-infrared laser light. For the compound isolated in Ar matrixes, near-IR excitation led to generation of two higher-energy conformers (GAC; AAT) differing from the most stable SSC form by 180° rotation around the C-C bond. A detailed investigation of this transformation revealed that one conformer (GAC) is produced directly from the near-IR-excited most stable conformer. The other higher-energy conformer (AAT) was effectively generated only upon excitation of the primary photoproduct (GAC) with another near-IR photon. Once these higher-energy conformers of glycolic acid were generated in an Ar matrix, they could be subsequently transformed into one another upon selective near-IR excitations. Interestingly, no repopulation of the initial most stable SSC conformer occurred upon near-IR excitation of the higher-energy forms of the compound isolated in solid Ar. A dramatically different picture of near-IR-induced conformational transformations was observed for glycolic acid isolated in N2 matrixes. In this case, upon near-IR excitation, the most stable SSC form converted solely into a new conformer (SST), where the acid OH group is rotated by 180°. This conformational transformation was found to be photoreversible. Moreover, SST conformer, photoproduced in the N2 matrix, spontaneously converted to the most stable SSC form of glycolic acid, when the matrix was kept at cryogenic temperature and in the dark.

Impact of Conventional and Microwave Heating on SAPO‐5 Formation and Brønsted Acidic Properties

AbstractThe hydrothermal crystallization of SAPO‐5 molecular sieves with Si mole ratios in the range of 0.05 to 0.13 was performed by either conventional or microwave heating to compare the influence of these two techniques on the isomorphous substitution of phosphorus by silicon atoms in the aluminophosphate framework. An extensive characterization of the obtained silicoaluminophosphates by ICP‐OES, SEM, XRD, TPDA, and MAS NMR spectroscopy indicated that conventional heating (drying oven) led to a better crystallinity and a higher content of isolated framework silicon atoms than microwave heating. While microwave heating has the advantage of reducing the crystallization time and conventionally prepared SAPO‐5 materials show better incorporation of isolated silicon atoms into the AFI framework according to the substitution mechanism SM IIa. This lower SM IIa substitution of tetrahedral framework sites by isolated silicon atoms in microwave‐prepared SAPO‐5 materials is the reason for their lower density of Brønsted acidic bridging OH groups [Si(OH)Al]. In contrast, the density of defect OH groups, such as weakly acidic SiOH groups, is higher than for conventionally prepared samples.

Hydrogen-Bond Acidity of OH Groups in Various Molecular Environments (Phenols, Alcohols, Steroid Derivatives, and Amino Acids Structures): Experimental Measurements and Density Functional Theory Calculations

The hydrogen-bond (H-bond) donating strengths of a series of 36 hydroxylic H-bond donors (HBDs) with N-methylpyrrolidinone have been measured in CCl4 solution by FTIR spectrometry. These data allow the definition of a H-bond acidity scale named pKAHY covering almost three pK units, corresponding to 16 kJ mol(-1). These results are supplemented by equilibrium constants determined in CH2Cl2 for one-third of the data set to study compounds showing a poor solubility in CCl4. A systematic comparison of these experimental results with theoretical data computed in the gas phase using DFT (density functional theory) calculations has also been carried out. Quantum electrostatic parameters appear to accurately describe the H-bond acidity of the hydroxyl group, whereas partial atomic charges according to the Merz-Singh-Kollman and CHelpG schemes are not suitable for this purpose. A substantial decrease of the H-bond acidity of the OH group is pointed out when the hydroxyl moiety is involved in intramolecular H-bond interactions. In such situations, the interactions are further characterized through AIM and NBO analyses, which respectively allow localizing the corresponding bond critical point and the quantification of a significant charge transfer from the available lone pair to the σ*OH antibonding orbital. Eventually, the H-bond ability of the hydroxyl groups of steroid derivatives and of lateral chains of amino acids are evaluated on the basis of experimental and/or theoretical data.

Synthesis, characterization and acid catalysis of solid acid from peanut shell

A strong Brønsted solid acid was synthesized by sulfonation of the partially carbonized agricultural biowaste peanut shell. The acidity of the Brønsted solid acid was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectra (FT-IR) and solid-state nuclear magnetic resonance (NMR) spectroscopy. The characterization results show that sulfonation on the peanut shell carbon produces a carbon based solid acid containing three functional Brønsted acid sites: weak acidic OH groups, strong acidic COOH and SO3H groups. The acid strength of the solid acid is stronger than that of HZSM-5(Si/Al=75), but still weaker than that of 100% H2SO4. The catalytic reaction tests indicate that this solid acid catalyst exhibits high activity and excellent recyclability for biodiesel production.

Solid-state NMR study of the kinetics and mechanism of dimethyl ether carbonylation on cesium salt of 12-tungstophosphoric acid modified with Ag, Pt, and Rh

By using 13C magic angle spinning (MAS) NMR, the mechanism of dimethyl ether (DME) carbonylation with carbon monoxide has been studied on solid metal-containing acidic cesium salt of 12-tungstophosphoric acid, M/Cs2HPW12O40 (M/HPA, M=Ag, Pt, and Rh). The kinetics of the reaction has been monitored with 1H MAS NMR in situ. Activation of DME occurs on acidic OH groups of M/HPA and gives rise to the surface methoxy groups at 293–473K. Carbon monoxide forms the surface metal–carbonyl complexes on M/HPA at 293–473K. The insertion of CO from the carbonyl into the CH3O bond of surface methoxide results in the acetate group attached to the Keggin anion, from which the target product, methyl acetate, is produced under the interaction with dimethyl ether. The reaction rate decreases in the following order: Rh/Cs2HPW12O40≫Pt/Cs2HPW12O40>Ag/Cs2HPW12O40, which correlates well with concentration of the reaction intermediates, methoxy groups, and metal–carbonyls. The higher concentration of these intermediates detected on Rh/Cs2HPW12O40 is in charge of the higher carbonylation rate on this catalyst with respect to M/HPA (M=Ag, Pt) catalysts.

Hydrothermal upgrading of algae paste: Application of 31P‐NMR

Although already proposed in the 1940s, hydrothermal upgrading of biomass, and specifically algae, to produce biocrude has only recently become a much researched topic. Algae are of special interest as they are capable of much higher biomass accumulation rates than terrestrial plants. To understand the transformation of algal biomass into biocrude, this process needs to be scrutinized in as much detail as possible to identify the most appropriate reaction conditions. It is usually not possible to identify individual transformation steps; however, in this article we demonstrate the use of 31P‐NMR to follow the fate of derivatized (2‐chloro‐4,4,5,5‐tetramethyl‐1,3,2‐dioxaphospholane) hydroxyl groups to start understand, which chemical species are involved in the initial degradation steps.Our data show the occurrence of a very fast degradation of acidic OH groups (derived from the hydrolysis of lipids) and aliphatic OH groups (derived from the fast hydrolysis of carbohydrates). The degradation of proteins leads to polyphenols, which appear to be rather stable even over prolonged treatment periods. Small quantities of aromatic compounds are also formed as secondary degradation products through sugar dehydration and cyclization as well as peptide transformation. It appears that additional deoxygenation routes exist as the deoxygenation rate using 31P‐NMR and that determined by elemental analysis differ. The formed oil (biocrude) is compared with typical North Sea oils using simulated distillation and was found to contain a significant high boiling faction, which would require further treatment (e.g., hydrocracking) to shift the boiling range to a more valuable oil composition. © 2013 American Institute of Chemical Engineers Environ Prog, 32: 1002–1012, 2013

Quantitative analysis of acidic OH groups in zeolite by ammonia IRMS-TPD and DFT: Application to BEA

The number and ammonia desorption enthalpy, as a measure of acid strength, of bridging OH groups divided into three portions based on the OH stretching frequency in zeolite β were measured by means of a method of ammonia infrared/mass spectroscopy (IRMS) temperature-programmed desorption (TPD). On the other hand, the optimized structures, wavenumbers and ammonia desorption energies (Edes) of all the geometrically possible acid sites located at crystallographically non-equivalent positions in a BEA structure were calculated with an aid of density functional theory (DFT). The calculated wavenumbers could be classified mainly into three portions. The interaction between H in the AlOHSi unit and oxygen atoms surrounding the unit is suggested to lower the OH frequency. The number, averaged Edes and wavenumber of stretching vibration of each portion were in agreement with the observed values.

Fundamental insights into conformational stability and orbital interactions of antioxidant (+)-catechin species and complexation of (+)-catechin with zinc(II) and oxovanadium(IV)

Conformational stability of (+)-catechin species in water has been examined with density functional theory, associated with the polarizable continuum model (PCM) of solvation. Factors such as electron delocalization, lone-pair electron donation and intramolecular hydrogen bonding substantially contribute to the conformational stabilization. Upon deprotonation, the HOMO and LUMO energies for (+)-catechin are both elevated; the energy gaps for the deprotonated species are narrower than the energy gap for the neutral species. The preferential deprotonation occurs at the C3′-, C5-, C7- and C4′-OH groups successively. The pKa value at 9.3 predicted for the most acidic OH group agrees well with previous experimental data; however the values are overestimated for the less acidic OH groups due to limitations of the PCM for charged solutes and/or complex nature of true deprotonation pathways. Formation of hydrogen radicals should be promoted at high pH values following the bond dissociation enthalpies. Complexation of (+)-catechin with either zinc(II) or oxovanadium(IV) is favored at the 1:1 metal-to-ligand (M:L) mole ratio, with the oxovanadium(IV) complex showing higher reaction preference. At M:L=1:2, formation of two isomeric complexes are plausible for each type of metal ion. Effects of stoichiometry and isomerism on the computational spectral features of the possibly formed metal complexes have been described.

Alkali Metal Modification of Silica Gel-Based Stationary Phase in Gas Chromatography

Modification of the precipitated silica gel was done by treatment with alkali metal (NaCl) before and after calcination. The silica surfaces before and after modification were confirmed by infrared spectroscopy in order to observe the strength and abundance of the acidic surface OH group bands which play an important role in the adsorption properties of polar and nonpolar solutes. The surface-modified silica gels were tested as GC solid stationary phases in terms of the separation efficiency for various groups of non-polar and polar solutes. Also, thermodynamic parameters (<svg style="vertical-align:-0.0pt;width:25.924999px;" id="M1" height="11.425" version="1.1" viewBox="0 0 25.924999 11.425" width="25.924999" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,11.363)"><path id="x394" d="M600 0h-557v24l268 633l28 8l261 -641v-24zM497 50l-194 489l-196 -489h390z" /></g><g transform="matrix(.017,-0,0,-.017,10.959,11.363)"><path id="x1D43B" d="M865 650q-1 -4 -4 -14t-4 -14q-62 -5 -77 -19.5t-29 -82.5l-74 -394q-12 -61 -0.5 -77t75.5 -21l-6 -28h-273l8 28q64 5 82 21t29 76l36 198h-380l-37 -197q-11 -64 0.5 -78.5t79.5 -19.5l-6 -28h-268l6 28q60 6 75.5 21.5t26.5 76.5l75 394q13 66 2 81.5t-77 20.5l8 28&#xA;h263l-6 -28q-58 -5 -75.5 -21t-30.5 -81l-26 -153h377l29 153q12 67 2 81t-74 21l5 28h268z" /></g> </svg>, <svg style="vertical-align:-0.23206pt;width:23.325001px;" id="M2" height="11.75" version="1.1" viewBox="0 0 23.325001 11.75" width="23.325001" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,11.4)"><use xlink:href="#x394"/></g><g transform="matrix(.017,-0,0,-.017,10.959,11.4)"><path id="x1D43A" d="M713 296l-5 -25q-47 -7 -59 -20t-23 -72l-15 -79q-9 -48 -3 -74q-15 -3 -55 -13t-63 -15t-59.5 -10t-70.5 -5q-149 0 -243 80t-94 220q0 169 127.5 276.5t336.5 107.5q91 0 206 -36l-10 -165l-29 -1q1 85 -47.5 126t-146.5 41q-153 0 -243.5 -97t-90.5 -242&#xA;q0 -122 68.5 -198.5t188.5 -76.5q121 0 139 75l20 86q13 58 -1.5 70.5t-99.5 20.5l5 26h267z" /></g> </svg>, and <svg style="vertical-align:-0.23206pt;width:19.174999px;" id="M3" height="11.75" version="1.1" viewBox="0 0 19.174999 11.75" width="19.174999" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,11.4)"><use xlink:href="#x394"/></g><g transform="matrix(.017,-0,0,-.017,10.959,11.4)"><path id="x1D446" d="M457 488l-30 -3q-17 148 -131 148q-53 0 -84.5 -34.5t-31.5 -82.5q0 -42 25.5 -72t74.5 -62l33 -22q63 -42 95 -85t32 -102q0 -84 -67 -137t-163 -53q-58 0 -113 22t-70 43l-4 152l27 4q4 -32 15 -62.5t31 -59.5t53.5 -47t76.5 -18q56 0 92 35t36 96q0 39 -25 70t-78 68&#xA;l-31 22q-32 23 -53.5 41.5t-45 57t-23.5 77.5q0 82 58 132.5t156 50.5q46 0 101 -17l18.5 -6t17 -6t8.5 -3q-4 -55 0 -147z" /></g> </svg>) were determined using <i >n</i>-hexane as a probe in order to show the adsorbate-adsorbent interaction. It was observed that the non-polar solutes could be separated Independent on the reactivity and porosity of the silica surfaces. The efficiency of the surface-modified silica gels to separate the aromatic hydrocarbons seemed to be strongly influenced by the density of the surface hydroxyls.

FTIR Evidence of Different Bonding of Methane to OH Groups on H–ZSM-5, HY, and SiO2

Low-temperature adsorption of CH4 and 15N2 on H–ZSM-5, SiO2, and HY is comparatively studied. Partly and fully deuteroxylated samples were also investigated. It was established that methane forms H bonds simultaneously with oxygen and hydrogen from the Si–OH groups, which reflects in enhanced shift of the OH modes to lower frequency as compared to the case if methane was bound to the proton only. In contrast, methane is attached to highly acidic hydroxyls forming a bond mainly with the proton. At high methane equilibrium pressure, a second methane molecule is bound to the same acidic OH group.

In situ MAS NMR investigation of the hydrogenation of acrylonitrile on Pt- and Rh-containing zeolites Y

This work presents first ex situ and in situ MAS NMR spectroscopic studies of the effect of noble metal reduction on the hydroxyl coverage of zeolites 0.9[Pt]Na-Y and 0.4[Rh]Na-Y and the hydrogenation of a double-bond-containing organic reactant, acrylonitrile. By 1H MAS NMR spectroscopy, it was found that the number of Brønsted acidic bridging OH groups (SiOHAl) formed upon noble metal reduction under flowing hydrogen nearly agrees with the number of the initially introduced complexes of bivalent metal cations. Hence, about 50% of the bivalent metal cations formed two SiOHAl groups per metal site upon reduction. After adsorption of reactants on the reduced metal-containing catalysts, no effect of the noble metals on the chemical shieldings of 13C nuclei of these molecules occurred. On the other hand, the 1H MAS NMR signals of reactant molecules adsorbed on zeolite 0.9[Pt]Na-Y have shown a significantly larger residual line width compared with those on zeolite 0.4[Rh]Na-Y, which indicates a higher mobility of reactants adsorbed on the latter zeolite. By in situ1H MAS NMR spectroscopy of the acrylonitrile hydrogenation carried out under semi-batch conditions at 295K, a reaction velocity on zeolite 0.4[Rh]Na-Y (r=7.0×10−3mmol/s) was determined, which is more than a factor six higher in comparison with that on zeolite 0.9[Pt]Na-Y (r=1.1×10−3mmol/s). During the initial period (t=12–24s) of the acrylonitrile hydrogenation on zeolite 0.4[Rh]Na-Y, weak 1H MAS NMR signals of temporary intermediates were observed. These temporary signals may be due to half-hydrogenated intermediates with short lifetime.

Electrochemical interfacial adsorption mechanism of polyphenolic molecules onto Hanging Mercury Drop Electrode surface (HMDE)

The electrochemical interfacial adsorption of a series of polyphenolic molecules (i.e. polyhydroxybenzoic acids) at the Hanging Mercury Drop Electrode (HMDE)–electrolyte interfaces were investigated using Square Wave-Adsorption Cathodic Stripping Voltammetry (SW-AdCSV) at pH 7.5. Polyhydroxybenzoic acids bearing one 4-hydroxybenzoic acid, two 3,4-dihydroxybenzoic acid (protocatechuic) or three 3,4,5-trihydroxybenzoic acid (gallic) OH-groups at positions C3, C4 and C5 on the benzene ring were studied. The complex interfacial electrochemical behaviour of these molecules has been deconvoluted to (i) adsorption evens and (ii) redox formations at the HMDE interface. The approach presented is based on the comparative analysis of the SW-AdCSV signals in conjunction with the molecular structure of the molecules. Accordingly, theoretical calculations, involving nonlinear-fit, resulted in the identification of the interfacial reaction mechanism of adsorbed gallic acid on the HMDE.

Addition of olefins to acetylacetone catalyzed by cooperation of Brønsted acid site of zeolite and gold cluster

HY zeolite-supported Au clusters (Au 0HY) prepared by deposition–precipitation method, well characterized by XANES, EXAFS, and NH 3- and acetyl acetone-adsorption IR, were tested for addition of acetyl acetone to alkenes. Au 0HY showed higher selectivity to the addition product than HY zeolite-supported Au(OH) 3 and Au clusters supported on NH 4 +-exchanged Y zeolite, Al 2O 3, MgO, SiO 2, and TiO 2. Studies on the effect of Au oxidation state, Au cluster size and Brønsted acidity of zeolite on the catalytic showed that co-presence of metallic Au with smaller cluster size and the acidic OH groups of the zeolite was necessary to the selective formation of the addition product. Cooperation mechanism of the Brønsted acid sites of the zeolite and Au clusters is proposed.

Prediction models for the Abraham hydrogen bond donor strength: comparison of semi‐empirical,ab initio, and DFT methods

Hydrogen bonding has a great impact on the partitioning of organic compounds in biological and environmental systems as well as on the shape and functionality of macromolecules. Electronic characteristics of single molecules, localized at the H‐bond (HB) donor site, are able to estimate the donor strength in terms of the Abraham parameterA. The quantum chemically calculated properties encode electrostatic, polarizability, and charge‐transfer contributions to hydrogen bonding. A recently introduced respective approach is extended to amides with more than one H atom per donor site, and adapted to the semi‐empirical AM1 scheme. For 451 organic compounds covering acidic CH, NH, and OH groups, the squared correlation coefficient is 0.95 for the Hartree–Fock and density functional theory (B3LYP) level of calculation, and 0.84 with AM1. The discussion includes separate analyses for weak, moderate, and strong HB donors, a comparison with the performance of increment methods, and opportunities for consensus modeling through the combined use of increment and quantum chemical methods. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Carbonylation of dimethyl ether on solid Rh-promoted Cs-salt of Keggin 12-H 3PW 12O 40: A solid-state NMR study of the reaction mechanism

The carbonylation of dimethyl ether (DME) with carbon monoxide on Rh-promoted cesium salt of 12-tungstophosphoric acid, Rh/Cs 2HPW 12O 40 (HPA), has been studied with 13C solid-state NMR. The bi-functional character of Rh/Cs 2HPW 12O 40 catalyst in halide-free carbonylation of DME has been directly demonstrated. The activation of the C–O bond of DME proceeds on Brønsted acid sites of HPA with the formation of the methyl group attached to the surface of HPA (methoxy species), whereas the role of rhodium consists in trapping carbon monoxide from gaseous phase and a transfer of CO to the center of DME activation, acidic OH-group of the catalyst, in the form of rhodium carbonyls. The lattice of Cs 2HPW 12O 40 makes it possible to locate these two different active centers in close proximity to each other, e.g., on two adjacent oxygen atoms, terminal and bridging, of one Keggin anion, thus facilitating the insertion of carbon monoxide from rhodium carbonyl into the C–O bond of methoxy-group to produce the acetate group bound to the Keggin anion. The latter offers finally methyl acetate under the interaction with DME, the intermediate surface methoxy-groups being restored.

Activation Energies for the Reaction of Ethoxy Species to Ethene over Zeolites

Dehydration of ethanol to ethene on acidic OH groups of zeolites was observed by infrared (IR) spectroscopy and temperature programmed desorption (TPD). The rate of decomposition of surface ethoxy groups was measured by measuring the amount of recovered acidic OH groups by IR, while confirming the evolution of ethene using a mass spectrometer, for the estimation of activation energy. The obtained activation energies for the evolution of ethene from ethoxy groups on hydrogen form mordenite, ZSM-5, and ferrierite zeolites were 161 ± 6, 181 ± 2, and 188 ± 2 kJ·mol−1, respectively. A tendency was found that the activation energy became larger in smaller-pored zeolite. The cause of the difference of three zeolites in activation energy for ethene evolution from ethoxy species is discussed along with an energy diagram described from reported theoretical examinations.

Synthesis, Structure, and Reversible Deprotonation of a Half-sandwich Iridium Complex Bearing a Chelating Oxime Ligand

Abstract A reaction of [{Cp*IrCl(μ-Cl)}2] (Cp* = η5-C5(CH3)5) with 1-(pyridin-2-yl)ethanone oxime (PyNOH) afforded the cationic oxime complex [Cp*IrCl(PyNOH)]Cl (3) with an acidic OH group at the β-position to the metal center. Complex 3 underwent reversible deprotonation to give the corresponding oximato complex [Cp*IrCl(PyNO)] (4), while treatment of 3 with silver triflate in acetonitrile led to the formation of the dicationic complex [Cp*Ir(PyNOH)(CH3CN)][OTf]2 (5, OTf = OSO2CF3). The detailed structures of 3–5 have been determined by X-ray crystallography.

Thermodynamic Features of the Reaction of Ammonia with the Acidic Proton of H-ZSM-5 As Studied by Variable-Temperature IR Spectroscopy

The interaction of ammonia with H-ZSM-5 zeolite (Si/Al = 11.5) was studied by means of variable-temperature infra-red spectroscopy, in the temperature range of 570−680 K. The interaction consists mainly in the reaction of ammonia with the zeolite Brønsted acid OH groups (absorbing at ca. 3610 cm−1) to form ammonium species that show a bending mode at ca. 1410 cm−1. From the changes in intensity of these IR absorption bands at 3610 and 1410 cm−1, with both temperature and NH3 equilibrium pressure, the standard enthalpy of reaction was calculated to be ΔH0 = −128 (±5) kJ mol−1. The corresponding entropy change is ΔS0 = −184 (±10) J mol−1 K−1, a figure suggesting that the ammonium cation interacting with the negative framework has little residual degrees of freedom. These results are discussed in the broader context of relevant data reported in the literature.

Shape-selective dissociative adsorption of alcohols on 1-butyl-3-methylimidazolium-exchanged mordenite zeolite

Dissociative alcohol adsorption was investigated on 1-butyl-3-methylimidazolium ([bmim]) exchanged mordenite ([bmim]M20) by Fourier transform infrared spectroscopy (FT-IR). Methanol, ethanol, 1-propanol and 2-propanol were adsorbed onto [bmim]M20. Although acidic OH groups were almost completely absent on [bmim]M20, bands attributed to hydrogen-bonded νOH of acidic OH groups (the so-called ABC triplet) were apparent for alcohol adsorption on [bmim]M20. This indicates the generation of acidic OH groups on [bmim]M20 by the dissociative adsorption of alcohols. Methanol and ethanol could diffuse into the [bmim]M20 micropores in the absence of observable energy barriers at room temperature, while energy barriers for diffusion into the micropores were observed for 1-propanol and 2-propanol at room temperature. The activation energy for diffusion of 2-propanol into the [bmim]M20 micropores was estimated as 25 kJ mol −1. Shape-selective adsorption into the [bmim]M20 micropores was revealed for the alcohols examined.