Кл.слова (ненормированные):
Adsorption -- Crystals -- Dichloromethane -- Hinges -- Nickel metallography -- Particle size -- Zinc metallography
Аннотация: The pillared layer framework DUT-8(Zn) (Zn2(2,6-ndc)2(dabco), 2,6-ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo-[2.2.2]-octane, DUT = Dresden University of Technology) is a prototypical switchable MOF, showing characteristic adsorption and desorption induced open phase (op) to closed phase (cp) transformation associated with huge changes in cell volume. We demonstrate switchability strongly depends on a framework-specific critical particle size (dcrit). Superposed, the solvent removal process (pore desolvation stress contracting the framework) significantly controls the cp/op ratio after desolvation and, subsequently, the adsorption induced switchability characteristics of the system. After desolvation, the dense cp phase of DUT-8(Zn) shows no adsorption-induced reopening and therefore is non-porous for N2 at 77 K and CO2 at 195 K. However, polar molecules with a higher adsorption enthalpy, such as chloromethane at 249 K and dichloromethane (DCM) at 298 K can reopen the macro-sized crystals upon adsorption. For macro-sized particles, the outer surface energy is negligible and only the type of metal (Zn, Co, Ni) controls the DCM-induced gate opening pressure. The node hinge stiffness increases from Zn to Ni as confirmed by DFT calculations, X-ray crystal structural analysis, and low frequency Raman spectroscopy. This softer Zn-based node hinges and overall increased stabilization of cp vs. op phase shift the critical particle size at which switchability starts to become suppressed to even lower values (dcrit ‹ 200 nm) as compared to the Ni-based system (dcrit ≈ 500 nm). Hence, the three factors affecting switchability (energetics of the empty host, (Eop–Ecp) (I), particle size (II), and desolvation stress (III)) appear to be of the same order of magnitude and should be considered collectively, not individually.
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Держатели документа:
Department of Inorganic Chemistry i, Technische Universitat Dresden, Bergstrasse 66, Dresden, 01069, Germany
Faculty of Chemistry and Pharmacy, University of Sofia, Sofia, 1126, Bulgaria
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, 660036, Russian Federation
Доп.точки доступа:
Abylgazina, L.; Senkovska, I.; Ehrling, S.; Bon, V.; St. Petkov, P.; Evans, J. D.; Krylova, S. N.; Крылова, Светлана Николаевна; Krylov, A. S.; Крылов, Александр Сергеевич; Kaskel, S.