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In this work, adsorption properties of the UiO-66 metal–organic framework were investigated, with particular emphasis on the influence of structural defects. A series of UiO-66 samples were synthesized and characterized using a wide range of experimental techniques. Type I adsorption isotherms for low-temperature adsorption of N2 and Ar showed that micropore volume and specific surface area significantly increase with the number of defects. Adsorption of hexane isomers in UiO-66 was studied by means of quasi-equilibrated temperature-programmed desorption and adsorption (QE-TPDA) experimental and Monte Carlo simulation techniques. QE-TPDA profiles revealed that only defect-free UiO-66 exhibits distinct two adsorption states. This technique also yielded high-quality adsorption isobars that were successfully recreated using Grand-Canonical Monte Carlo molecular simulations, which, however, required refinement of the existing force fields. The calculations demonstrated the detailed mechanism of adsorption and separation of hexane isomers in the UiO-66 structure. The preferred tetrahedral cages provide suitable voids for bulky molecules, which is the reason for unusual “reverse” selectivity of UiO-66 towards di-branched alkanes. Interconnection of the tetrahedral cavities due to missing organic linkers greatly reduces the selectivity of the defected material.

MWW type zeolites are characterized by the presence of zeolitic layers of 2.5 nm thickness, containing 10-member ring sinusoidal channels inside and supercavities with 12-member ring openings located on their surfaces. Expansion and pillaring of layered zeolites increase the access to active sites and can enable or facilitate catalytic activity towards larger reactant molecules. This goal is explored in this work reporting the pillaring of layered zeolite MCM-56 with MWW topology by tetraethylorthosilicate (TEOS) treatment with the assistance of isopropanol, aimed at obtaining hierarchical micro-mesoporous systems. MCM-56 (Si/Al = 12) was synthesized with hexamethyleneimine as a structure-directing and aniline as a structure-promoting agent. Hierarchical porous systems were obtained using two different pillaring methods: (1) with TEOS only and (2) with TEOS mixed with isopropanol. The MWW framework was preserved during swelling/pillaring in both methods. Pillared zeolites obtained via alcohol-assisted pillaring possessed unique intermediate micro-mesopores with the size of about 2 nm. IR study revealed a decrease in the concentration of accessible acid centers upon pillaring. However, the fraction of acid sites on the external surface, accessible for adsorption of large molecules, increased by up to 90%. Catalytic activity was evaluated in the Friedel-Crafts alkylation of mesitylene with benzyl alcohol. Pillaring resulted in reduction of the acid site concentrations, but the materials retained high catalytic activity. Pillaring in the presence of alcohol produced increased turnover frequency values based on the concentrations of the external acid sites.

[EN] Adsorption of n-alkanes from pentane to decane (C5¿C10) in zeolites LTA (ITQ-29 and 5A) and faujasite (FAU, dealuminated high-silica Na-FAU, NaY, and NaX) as well as branched hexane isomers in FAU was investigated by means of experimental quasi-equilibrated temperature-programmed desorption and adsorption (QE-TPDA) and theoretical Monte Carlo molecular simulations. A novel QE-TPDA method of studying porosity provided high-quality desorption¿adsorption profiles and adsorption isobars of hydrocarbons. A unique two-step adsorption of long-chain alkanes in LTA zeolites was observed and explained in detail based on the results of the theoretical calculations. Although adsorption of n-alkanes in FAU is a one-step process, it also does not occur in a uniform manner because of strong lateral interactions at high loadings. We also investigated the influence of cation content on adsorption equilibrium and energetics for the studied adsorbent¿adsorbate systems, finding a nonlinear relation between heat of adsorption and content of cations in FAU. Investigations on packing of the molecules of n-alkanes were also performed, revealing relations between chain length of the probe molecule and sorption capacity of the studied materials., This work was supported by the National Science Centre, Poland, grant no. 2016/21/N/ST5/00868, and from Spanish Ministerio de Economiay Competitividad (CTQ2016-80206P), and by the Andalucia Region (FQM-1851). The authors also thank C3UPO for the HPC support. The authors obtained financial resources as part of financing the doctoral scholarship from the National Science Center, Poland, grant no. 2018/28/T/STS/00274.