Highly efficient metal/solvent-free chemical fixation of CO2 at atmospheric pressure conditions using functionalized porous covalent organic frameworks

A rare demonstration of metal/solvent-free chemical fixation of CO 2 into value-added cyclic carbonates under mild atmospheric pressure conditions using polar-functionalized COF is presented. • Rational design of a bifunctional COF catalyst for metal/solvent-free efficient fixation of CO 2 under mild conditions is achieved. • The effect of polar functionality on the catalytic activity of the COF is demonstrated. • The COF exhibits high catalytic activity, excellent chemical stability and recyclability for several cycles of reuse. The development of metal-free heterogeneous catalysts for selective carbon capture and utilization (CCU) as a C1-feedstock under mild conditions has significant potential towards sustainable fixation of atmospheric CO 2 into value-added products. Herein, we report utilization of polar functionalized covalent-organic framework (COF-SO 3 H) as metal-free heterogeneous catalyst for efficient fixation of CO 2 into cyclic carbonates. The COF-SO 3 H possesses large 1D channels functionalized with polar (–NH, and –SO 3 H) groups rendering selective adsorption property for CO 2 with a high heat of interaction (Q st ) energy of 42.2 kJ/mol. Interestingly, the value of Q st for COF-SO 3 H was found to be about 10.8 kJ/mol higher than that of analogous COF (COF-H) which lacks the polar sulfonic acid group. The presence of basic –NH sites combined with Brønsted acid (–SO 3 H) sites make COF-SO 3 H a suitable material for metal/solvent-free chemical fixation of CO 2 with epoxides. Indeed, COF-SO 3 H catalyzes cycloaddition of CO 2 with epoxides to generate cyclic carbonates under metal/solvent-free atmospheric pressure conditions. Moreover, COF-SO 3 H is highly recyclable for several cycles with retaining the catalytic activity and structural rigidity. This work represents a rare demonstration of metal/solvent-free chemical fixation of CO 2 under atmospheric pressure conditions using polar-functionalized COF.