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

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.