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.

Due to its exceptional chemical and thermal stability, ZIF-8 is one of the most promising representatives of nanoporous metal-organic frameworks. In this work, we investigate adsorption properties of this material both experimentally and theoretically. The experiments were carried out on 8 preparations differing in morphology of the crystals. Adsorption was studied in isothermal approach exploiting standard adsorbates, such as N₂ or CO₂, as well as in isobaric regime with C5–C9 linear alkanes. The latter were performed with the novel quasi-equilibrated temperature-programmed desorption and adsorption (QE-TPDA) technique showing that a complexity of n-alkanes adsorption mechanism in ZIF-8 depends on the nature of adsorbate. Unexpectedly, for adsorption of C7–C9 n-alkanes a two-step process was found. QE-TPDA yielded high quality adsorption isobars which were successfully reproduced by Grand-Canonical Monte Carlo molecular simulations. The calculations showed that the specific adsorption behaviour of ZIF-8 is due to the fact that its structure undergoes conformational changes in order to adapt to the guest molecules. QE-TPDA measurements with n-nonane were performed at conditions close to saturation of the adsorbate. This allowed to observe surface-related adsorption on the ZIF-8 crystals, which was correlated with their size.