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 P 2 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 ${P\bar 3}$ c 1 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 .