Porous nitrogen-rich covalent organic framework for capture and conversion of CO2 at atmospheric pressure conditions

A porous nitrogen-rich imine-linked covalent organic framework (COF1) has been synthesized by Schiff-base condensation reaction of 4,4′-azodianiline (AZO) and benzene-1, 3, 5-tricarboxaldehyde (BTA) under solvothermal conditions and characterized by various techniques. Owing to the presence of basic imine (-CN) and -azo (-NN) functionalized 1D channels, COF1 exhibits high affinity for CO2 with high isosteric heat of adsorption (Qst) value of 32.3 kJ/mol. Further, the COF1 supported ZnBr2 acts as an excellent recyclable catalyst for cycloaddition of CO2 to epoxides resulting in cyclic carbonates with high yield and 100% selectivity under solvent-free mild conditions of 1 bar of CO2. Further, the coordination of Zn(II) to basic –CN group was supported by XPS studies and theoretical calculations. Interestingly, COF1 shows excellent recyclability and can be recycled for several cycles without substantial loss of catalytic activity and structural rigidity. The high CO2 affinity combined with excellent thermal stability and catalytic activity make COF1 a promising candidate material for efficient fixation of carbon dioxide.