Two robust porous metal-organic frameworks sustained by distinct catenation: selective gas sorption and single-crystal-to-single-crystal guest exchange.
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abstract
Assembly of copper(I) halide with a new tripodal ligand, benzene-1,3,5-triyl triisonicotinate (BTTP4), afforded two porous metal-organic frameworks, [Cu(2)I(2)(BTTP4)]2CH(3)CN (12CH(3)CN) and [CuBr(BTTP4)](CH(3)CNCHCl(3)H(2)O) (2solvents), which have been characterized by IR spectroscopy, thermogravimetry (TG), single-crystal, and powder X-ray diffraction (PXRD) methods. Compound 1 is a polycatenated 3D framework that consists of 2D (6,3) networks through inclined catenation, whereas 2 is a doubly interpenetrated 3D framework possessing the ThSi(2)-type (ths) (10,3)-b topology. Both frameworks contain 1D channels of effective sizes 912 and 1010 (2), which amounts to 43 and 40% space volume accessible for solvent molecules, respectively. The TG and variable-temperature PXRD studies indicated that the frameworks can be completely evacuated while retaining the permanent porosity, which was further verified by measurement of the desolvated complex [Cu(2)I(2)(BTTP4)] (1'). The subsequent guest-exchange study on the solvent-free framework revealed that various solvent molecules can be adsorbed through a single-crystal-to-single-crystal manner, thus giving rise to the guest-captured structures [Cu(2)I(2)(BTTP4)]C(6)H(6) (1benzene), [Cu(2)I(2)(BTTP4)]2C(7)H(8) (12toluene), and [Cu(2)I(2)(BTTP4)]2C(8)H(10) (12ethylbenzene). The gas-adsorption investigation disclosed that two kinds of frameworks exhibited comparable CO(2) storage capacity (86-111 mL g(-1) at 1 atm) but nearly none for N(2) and H(2), thereby implying its separation ability of CO(2) over N(2) and H(2). The vapor-adsorption study revealed the preferential inclusion of aromatic guests over nonaromatic solvents by the empty framework, which is indicative of selectivity toward benzene over cyclohexane.
