Two Zn(II) metal-organic frameworks with coordinatively unsaturated metal sites: structures, adsorption, and catalysis.

Assembly of Zn(NO(3))(2) with the tripodal ligand H(3)TCPB (1,3,5-tri(4-carboxyphenoxy)benzene) affords two porous isoreticular metal-organic frameworks, [Zn(3)(TCPB)(2)⋅2DEF]⋅3DEF (1) and [Zn(3)(TCPB)(2)⋅2H(2)O]⋅2H(2)O⋅4DMF (2). Single-crystal X-ray diffraction analyses reveal that 1 crystallizes in the monoclinic space group P2(1)/c and possesses a 2D network containing 1D microporous opening channels with an effective size of 3.0×2.9 Å(2), whereas 2 crystallizes in the trigonal space group P3c1 and also possesses a 2D network containing 1D channels, with an effective aperture of 4.0×4.0 Å(2). TOPOS analysis reveals that both 1 and 2 have a (3,6)-connected network topology with the Schläfli symbol of (4(3)⋅6(12)) (4(3))(2). According to the variable-temperature powder X-ray diffraction patterns, the solid phase of 1 can be converted into that of 2 during a temperature-induced dynamic structural transformation, thus indicating that the framework of 2 represents the most thermally stable polymorph. Desolvated 2 exhibits highly selective adsorption behaviors toward H(2)/N(2), CO(2)/N(2), and CO(2)/CH(4); furthermore, it displays size-selective catalytic activity towards carbonyl cyanosilylation and Henry (nitroaldol) reactions.