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JUK-8 ([Zn(oba)(pip)]n, oba2– = 4,4′-oxybis(benzenedicarboxylate), pip = 4-pyridyl-functionalized benzene-1,3-dicarbohydrazide) is a hydrolytically stable flexible metal-organic framework. Owing to its unusual adsorptive properties, JUK-8 can be considered as a promising sensing material for construction of detectors of volatile organic compounds (VOCs) in air. Quasi-equilibrated temperature-programmed desorption and adsorption (QE-TPDA) is a versatile method dedicated to characterization of porous materials. In this work, QE-TPDA was employed to study co-adsorption of water and selected alcohols in JUK-8. For the first time an infrared detector sensitive to organic compounds was used in the QE-TPDA measurements, allowing the study of the influence of water vapor on sorption of VOCs. The QE-TPDA profiles of the studied alcohols, exhibiting two desorption maxima and two adsorption minima, are consistent with the standard sorption isotherms, revealing a two-step adsorption–desorption mechanism. The profiles recorded in the presence of water are noticeably changed in different ways for different alcohols. While at low relative humidity (RH) (ca. 20%) the low temperature adsorption states of ethanol and 1-propanol were only slightly destabilized, for 2-propanol almost complete suppression of adsorption was observed. The results found for moderate RH levels (ca. 50%) indicated that the opening of the JUK-8 structure, responsible for its breathing behavior, was followed by the filling of the just generated pores with a water–alcohol mixture. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The rapidly rising level of carbon dioxide in the atmosphere resulting from human activity is one of the greatest environmental problems facing our civilization today. Most technologies are not yet sufficiently developed to move existing infrastructure to cleaner alternatives. Therefore, techniques for capturing carbon dioxide from emission sources may play a key role at the moment. The structure of the UiO‐66 material not only meets the requirement of high stability in contact with water vapor but through the water pre‐adsorbed in the pores, the selectivity of carbon dioxide adsorption is increased. We successfully applied the recently developed methodology for water adsorption modelling. It allowed to elucidate the influence of water on CO2 adsorption and study the mechanism of this effect. We showed that water is adsorbed in octahedral cage and stands for promotor for CO2 adsorption in less favorable space than tetrahedral cages. Water plays a role of a mediator of adsorption, what is a general idea of improving affinity of adsorbate. On the basis of pre‐adsorption of methanol as another polar solvent, we have shown that the adsorption sites play a key role here, and not, as previously thought, only the interaction between the solvent and quadrupole carbon dioxide. Overall, we explained the mechanism of increased CO2 adsorption in the presence of water and methanol, as polar solvents, in the UiO‐66 pores for a potential post‐combustion carbon dioxide capture application. [ABSTRACT FROM AUTHOR]

Discrete molecular species that can perform certain functions in response to multiple external stimuli constitute a special class of multifunctional molecular materials called smart molecules. Herein, cyanido‐bridged coordination clusters {[FeII(2‐pyrpy)2]4[MIV(CN)8]2}⋅4 MeOH⋅6 H2O (M=Mo (1 solv), M=W (2 solv) and 2‐pyrpy=2‐(1‐pyrazolyl)pyridine are presented, which show persistent solvent driven single‐crystal‐to‐single‐crystal transformations upon sorption/desorption of water and methanol molecules. Three full desolvation–resolvation cycles with the concomitant change of the host molecules do not damage the single crystals. More importantly, the Fe4M2 molecules constitute a unique example where the presence of the guests directly affects the pressure‐induced thermal spin crossover (SCO) phenomenon occurring at the FeII centres. The hydrated phases show a partial SCO with approximately two out‐of‐four FeII centres undergoing a gradual thermal SCO at 1 GPa, while in the anhydrous form the pressure‐induced SCO effect is almost quenched with only 15 % of the FeII centres undergoing high‐spin to low‐spin transition at 1 GPa. [ABSTRACT FROM AUTHOR]

Layered zeolite materials with FER layer topology can produce various condensed and expanded structures including zeolite frameworks, FER and CDO, their interlayer expanded forms (IEZ), and organic-intercalated and pillared derivatives. This work concerns pillaring of the surfactant-swollen derivative with a gallery height of ca. 2.5 nm between layers by treatment with tetraethylorthosilicate (TEOS) at room and elevated temperatures. The materials obtained at 100 °C and higher showed unusual properties including 2 nm pores on the micro/mesoporous border and disordered layer packing indicated by the absence of distinct low angle interlayer peaks at d-spacing ＞3 nm (∼3° 2ϑ Cu Kα radiation) in the X-ray diffraction pattern (XRD). TEOS treatment at room temperature produced a pillared molecular sieve with the expected mesoporous characteristics, namely a pore size of around 3 nm and a high intensity low angle (001) peak at 2.3° 2ϑ, and a d-spacing of 3.8 nm, in the XRD. The characterization aiming to elucidate the nature of the obtained unusual products included gas adsorption isotherms, aberration corrected (Cs-corrected) Scanning Transmission Electron Microscopy (STEM) studies and 29Si solid state NMR. BET surface area values decreased with the temperature of TEOS treatment from approximately 1200 m2 g−1 to ∼900 and 600 m2 g−1, at room temperature, 100 °C, and 120 °C, respectively. The 29Si solid state NMR revealed the presence of both Q3 ((SiO)3SiOX, X = H or minus charge) and Q4 ((SiO)4Si) centers giving separated signals up to the pillaring step. After pillaring at 100 °C and calcination, the nominal intensity ratios Q4 : Q3 were 2.17 and 2.61 but the signals were merged into one broad peak indicating the structural heterogeneity of Si–O coordination. The microscopy showed the presence of FER layers in the samples but the overall structure and composition were not well-defined. The observed unusual disorganization and possible partial degradation of layers during pillaring may result from the combination of high temperature, alkalinity (surfactant hydroxide) and siliceous composition of the layers. The obtained pillared products are of interest for the preparation of larger pore catalysts and sorbents or controlled drug delivery. [ABSTRACT FROM AUTHOR]

Many chemical compositions produce layered solids consisting of extended sheets with thickness not greater than a few nanometers. The layers are weakly bonded together in a crystal and can be modified into various nanoarchitectures including porous hierarchical structures. Several classes of 2-dimensional (2D) materials have been extensively studied and developed because of their potential usefulness as catalysts and sorbents. They are discussed in this review with focus on clays, layered transition metal oxides, silicates, layered double hydroxides, metal(iv) phosphates and phosphonates, especially zirconium, and zeolites. Pillaring and delamination are the primary methods for structural modification and pore tailoring. The reported approaches are described and compared for the different classes of materials. The methods of characterization include identification by X-ray diffraction and microscopy, pore size analysis and activity assessment by IR spectroscopy and catalytic testing. The discovery of layered zeolites was a fundamental breakthrough that created unprecedented opportunities because of (i) inherent strong acid sites that make them very active catalytically, (ii) porosity through the layers and (iii) bridging of 2D and 3D structures. Approximately 16 different types of layered zeolite structures and modifications have been identified as distinct forms. It is also expected that many among the over 200 recognized zeolite frameworks can produce layered precursors. Additional advances enabled by 2D zeolites include synthesis of layered materials by design, hierarchical structures obtained by direct synthesis and top-down preparation of layered materials from 3D frameworks. [ABSTRACT FROM AUTHOR]