Selective CO2 adsorption and Lewis acid catalytic activity towards naphthimidazole synthesis by a Zn-MOF

A two-fold interpenetrated, three dimensional Zn-based porous MOF, {[Zn(BPBA)Cl]⋅5H2O}n (1) [BPBA = 3,5-bis-(4-oxo-4H-pyridin-1-yl)-benzoate], has been synthesized at high temperature under solvothermal conditions by the in situ acidic hydrolysis of the tripodal ligand 3,5-bis-(4-oxo-4H-pyridin-1-yl)-benzonitrile (BPBN). The de-solvated MOF exhibited selective CO2 adsorption at a temperature of 195 K and 1 bar pressure over N2 and H2. Interestingly, the four coordinated Zn(II) sites in the MOF exhibited high Lewis acidic heterogeneous catalytic activity for the synthesis of naphthimidazole in excellent yield without pre-activation of the MOF. The Zn(II) sites could directly coordinate to the substrate to catalyze the chemical transformation by an expansion of the coordination number. The π-π supramolecular interactions between the aromatic rings of the framework and the substrate molecule might help in the substrate activation.