Double−Step Gas Sorption of a Two−Dimensional Metal−Organic Framework

Abstract

The synthesis, structural changes, and nitrogen gas sorption isotherm of a porous metal−organic framework (PMOF) comprising stacked two-dimensional sheets are reported. This compound easily loses guest molecules and shrinks its interlayer distance. The guest-free species show a unique double-step sorption isotherm. Sorption and X-ray structural analyses have clarified that the first uptake is a micropore filling, while the second uptake originates from a clathrate formation. This explains the total sorption amount corresponding to about the double of the original void volume of the crystals.

An Interpenetrated Framework Material with Hysteretic CO2 Uptake

“…In contrast, the pressure at which we observe the step and hysteresis in the CO 2 isotherm is far below the saturation pressure (34.3 atm at 273 K), apparent in the high-pressure isotherms (see the Supporting Information). Similar behavior has been reported for the adsorption of nitrogen by a two-dimensional framework material [35] and by a three-dimensional pillared paddlewheel structure, but is otherwise unknown. [20,36] The N 2 and Ar isotherms of YO-MOF display a fairly unusual gated adsorption behavior (see Figure 4 and the Supporting Information).…”

Fluorine-functionalized metal–organic frameworks and porous coordination polymers

“…In fact, it was experimentally proven that this MOF showed high equilibrium and kinetic separation for CO 2 over CH 4 under realistic conditions, using a mixed gas at room temperature and in a humid environment (Figure 10b and c). The moderate heat of CO 2 adsorption (Q st = -18 to − 31 kJ mol − 1 ), which was experimentally determined, and the calculated interaction energy using a model structure (Figure 10d) 32 suggested that the fluorine atoms of the weakly coordinated PF 6 − anions contribute to the interaction sites with adsorbed CO 2 molecules. To elucidate the interactions between inorganic fluorinated monoanions and guest molecules in detail, it is important to determine the crystal structures with adsorbed guest molecules.…”

“…31,53 After this finding, the derivatives [M(A) 2 (4,4′-bpy) 2 ] (M= Cu, A = CF 3 SO 3 ; M= Cu, A = PF 6 ; M = Co and A = CF 3 SO 3 ) were separately reported. [32][33][34] These MOFs formed similar two-dimensional square-grid frameworks with weakly coordinated CF 3 SO 3 − and PF 6 − (Cu), and coordinated CF 3 SO 3 − (Co) monoanions but showed different sorption behaviors from the parent ELM-11; there were two sorption events: the first uptake was a micropore filling and the second uptake was caused by a gate-sorption process with an expansion of the interlayer distance and sliding between the layers. Using these anions, it is also possible to fabricate one-dimensional flexible MOFs exhibiting gate sorption.…”

Cu2(pzdc)2L [L=dipyridyl-based ligands] porous coordination polymers: Hysteretic adsorption and diffusion kinetics of CO2 and CH4

“…Many flexible MOFs exhibit an interesting gate-opening phenomenon where the framework structures suddenly changes from a relatively closed structure to an open one and due to guest-induced framework transition [44,[58][59][60][61]. Kitagawa Inspection of Fig.…”