Amino functionalized Zn/Cd-metal–organic frameworks for selective CO2 adsorption and Knoevenagel condensation reactions

Abstract

Two amino functionalized Metal–Organic Frameworks (MOFs), {[Zn(Py₂TTz)(2-NH₂-BDC)]·(DMF)}_n (1) and {[Cd(Py₂TTz)(2-NH₂-BDC)]·(DMF)·0.5(H₂O)}_n (2) (where Py₂TTz = 2,5-bis(4-pyridyl)thiazolo[5,4-d]thiazole, 2-NH₂-BDC = 2-amino-1,4-benzenedicarboxylate, and DMF = N,N-dimethylformamide), were synthesized and characterized using the primary ligand 2-amino-1,4-benzenedicarboxylic acid (2-NH₂-H₂BDC) and the auxiliary ligand 2,5-bis(4-pyridyl)thiazolo[5,4-d]thiazole (Py₂TTz). They possess similar 2-fold interpenetrated three-dimensional bipillared-layer framework structures composed of typical binuclear metal nodes, 2-NH₂-BDC two-dimensional layers and Py₂TTz bipillars. Notably, thiazole nitrogen atoms and pendant –NH₂ groups are present in channels in the two frameworks. Given their good chemical stabilities, high thermal stabilities, and exposed nitrogen sites, gas adsorption and catalytic experiments of the two MOFs were performed. The results demonstrate that MOF 2 can selectively adsorb carbon dioxide gas; moreover, the two MOFs can be employed as recyclable heterogeneous catalysts for Knoevenagel condensation reactions under solvent-free conditions.