Abstract:
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 CO2
into value-added products. Herein, we report utilization of polar functionalized covalent-organic framework
(COF-SO3H) as metal-free heterogeneous catalyst for efficient fixation of CO2 into cyclic carbonates. The COFSO3H possesses large 1D channels functionalized with polar (–NH, and –SO3H) groups rendering selective
adsorption property for CO2 with a high heat of interaction (Qst) energy of 42.2 kJ/mol. Interestingly, the value
of Qst for COF-SO3H 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 (–SO3H) sites make
COF-SO3H a suitable material for metal/solvent-free chemical fixation of CO2 with epoxides. Indeed, COF-SO3H
catalyzes cycloaddition of CO2 with epoxides to generate cyclic carbonates under metal/solvent-free atmospheric
pressure conditions. Moreover, COF-SO3H 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 CO2 under atmospheric pressure conditions using polar-functionalized COF.
