Two Robust Porous Metal–Organic Frameworks Sustained by Distinct Catenation: Selective Gas Sorption and Single‐Crystal‐to‐Single‐Crystal Guest Exchange

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 (1·2CH(3)CN) and [CuBr(BTTP4)]⊃(CH(3)CN·CHCl(3)·H(2)O) (2·solvents), 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 9×12 and 10×10 Å(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) (1·benzene), [Cu(2)I(2)(BTTP4)]⊃2C(7)H(8) (1·2 toluene), and [Cu(2)I(2)(BTTP4)]⊃2C(8)H(10) (1·2 ethylbenzene). 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.