Stoichiometry Controlled Structural Variation in Three-Dimensional Zn(II)–Frameworks: Single-Crystal to Single-Crystal Transmetalation and Selective CO2 Adsorption

Abstract

Solvothermal reaction of the tripodal linker tris(4′-carboxybiphenyl)amine (H3L) and the colinker 3,5-di(pyridin-4-yl)-4H-1,2,4-triazol-4-amine (dpta) in a different molar ratio produced 2-fold interpenetrated but structurally different three-dimensional Zn(II) frameworks: {[Zn3(L)2(dpta)(DMF)]·18DMF·3H2O}n (1) and {[Zn3(L)2(dpta)(DMF)]·14DMF·3H2O}n (2) (L = L3-, DMF = N,N′-dimethylformamide). Both the structures are built with a common [Zn3(COO)6] secondary building unit. While 1 is a pillared-bilayer framework with (43·624·8)(43)2 topology, the construction of 2 is different due to altered disposition of SBUs and is describable by the Schlafli symbol (43.58.68.78.8)(43)2. The structural variation alters the electronic environment and pore sizes in these frameworks, which allows the activated framework 2′ to uptake better N2 and H2 gases at 77 K, and CO2 at 273 K, than 1′. Compared to 1′, framework 2′ gives better selectivity of CO2 adsorption over N2, and H2 at 273 K, although the selectivity of CO2 ove...