Methane Sorption and Structural Characterization of the Sorption Sites in Zn₂(bdc)₂(dabco) by Single Crystal X‐ray Crystallography

Abstract

Sorption isotherms of methane in Zn(2)(bdc)(2)(dabco) are measured up to a pressure of 35 bar in the temperature range between 198-296 K. The methane sorption measurements at 296 K showed an uptake of 137 cm(3) cm(-3) at 35 bar. The enthalpy of methane adsorption for Zn(2)(bdc)(2)(dabco) estimated by the virial equation is 13.6 kJ mol(-1) at zero coverage. X-ray structure analysis of methane-adsorbed Zn(2)(bdc)(2)(dabco) by synchrotron radiation at 90 K revealed that methane molecules occupy three independent sorption sites (A, B, and C) with a stoichiometry of Zn(2)(bdc)(2)(dabco) x 6.69 CH(4), which is consistent with the results of the gas sorption measurements at 198 K. In a cavity, eight symmetry-related methane sorption sites A are located near the {Zn(2)(CO(2))(4)} paddle-wheel units, while four symmetry-related methane sorption sites B are near the center of the small windows along the a and b axes. Both A and B sites are half-occupied. Methane molecules occupying sites A are not only in van der Waals contact with the paddle-wheel units, but also interact with the phenyl rings of bdc ligands through partial pi-HC interactions. Methane molecules in B sites interact with the side of the phenyl rings through van der Waals interaction. The site C, located at the center of the cavity, is a secondary sorption site; methane molecules occupying sites C are in van der Waals contact with those in sites A and B.

13C NMR study of diffusion anisotropy of carbon dioxide adsorbed in nanoporous DMOF-1

“…¼ 3:7 Â 10 9 m 2 s À1 , which would indicate a preferential one-dimensional diffusion in channel direction with an anisotropy of g ¼ 3, or for example D k ¼ 2:6 Â 10 9 m 2 s À1 and D ? ¼ 7:8 Â 10 9 m 2 s À1 , which would indicate a preferential twodimensional diffusion with an anisotropy of g ¼ 1 3 .…”

“…Small molecules like alkanes [2,3], alcoholes [4,5] and carbon dioxide [6][7][8] may be adsorbed in the nanochannels after removal of the initial solvents by activation. With respect to study host-guest interaction in this MOF, carbon dioxide is of special interest since the 13 C chemical shift tensor of the CO 2 molecule displays an anisotropy as large as À335 ppm [9].…”

CO2 adsorption, selectivity and water tolerance of pillared-layer metal organic frameworks

“…Arstad et al reported a CO 2 adsorption capacity of 14.8 mol/kg at 25°C and 24 bar for Ni 2 (BDC) 2 (Dabco) [14]. Several groups have reported that Zn 2 (BDC) 2 (Dabco) has a high CH 4 storage capacity [33,35].…”

“…A systematic modulation of organic ligands (L) leads also to a series of porous isomorphous MOFs Zn 2 (L) 2 (Dabco), with varying size of pores. Recently promising results have been obtained for the application of pillared-layer MOFs in adsorption and storage of gases such as CO 2 and CH 4 [33][34][35][36][37]. Arstad et al reported a CO 2 adsorption capacity of 14.8 mol/kg at 25°C and 24 bar for Ni 2 (BDC) 2 (Dabco) [14].…”

Fabrication of supramolecular frameworks by tuning the binding site of a tripodal ligand with d 10 metal ions: Interplay of covalent and non-covalent interactions in solid-state structure

“…Design and synthesis of metal-organic frameworks of Zn(II) and Cd(II) are important due to their functionalities in molecular motors, bio-mimicking models, optoelectronic devices, catalytic activity and as anion exchanger. [23][24][25][26] The advantage of using these d 10 systems as a node in such designed synthesis lies in their flexibility in co-ordination geometry. 24,25 Among the bridging ligands 2,4,6-tri(4-pyridyl)-1,3,5-triazine (tpt) has been used efficiently to exploit its tridentate nature to design different type of coordination frameworks.…”