RESUMO
Metal-organic frameworks (MOFs) possess unique flexibility of structure and properties, which drives them toward applications as water adsorbents in many emerging technologies, such as adsorptive heat transformation, water harvesting from the air, dehumidification, and desalination. A deep understanding of the surface phenomena is a prerequisite for the target-oriented design of MOFs with the required adsorption properties. In this work, we comprehensively study the effect of functional groups on water adsorption on a series CAU-10-X substituted with both hydrophilic (X = NH2) and hydrophobic (X = NO2) groups in the linker. The adsorption equilibrium is measured at P = 7.6-42 mbar and T = 5-100 °C. The study of water adsorption by a set of mutually complementary physicochemical methods (TG, XRD in situ, FTIR, and 1H NMR relaxometry) elucidates the nature of primary adsorption sites and water adsorption mechanisms.
RESUMO
The effect of a "guest-host" interaction on the phase composition and sorption properties of the composite sorbents "salt in a porous host matrix" has been studied. The matrix was a mesoporous silica of KSK type, while the confined salts were CaCl(2), CuSO(4), MgSO(4), and Na(2)SO(4). Both structure and properties of the composites were studied by X-ray diffraction, titration in the pH range of 2-9, differential dissolution, and TG techniques. Chemical interaction between the silica surface and the salt during preparation results in the formation of the salt surface complexes and stabilization of the dispersed salt in two phases, namely, a crystalline phase and an X-ray amorphous phase. The water sorption properties of the composites depend on the phase composition and can be intently modified by using variation of the preparation conditions.
