Prudent Choice of Iron-based Metal-Organic Networks for Solvent-free CO2 Fixation at Ambient Pressure

The rising global warming and associated climate change demand efficient tactics to reduce CO2 concentration in the atmosphere. Conversion of epoxides to cyclic carbonates utilizing CO2 is a promising and sustainable approach towards CO2 fixation. However, the inert nature of CO2 and high activation energy requirement for the particular reaction necessitate the use of efficient catalysts. In this work, we have designed and developed a heterogeneous catalyst using catechol functionalized guanidinium based ligands (L1) and Fe(III) ions to perform the CO2 fixation reaction. The resulting amorphous material (Fe-L1) possesses metal-organic network as revealed through different characterization methods. The optimized catalyst Fe-L1 is efficient for the conversion of a variety of epoxides into their corresponding cyclic carbonates in very good yield (>80 %). The reactions were performed under atmospheric pressure without solvent and external additives (e. g., TBAI or KI). The investigation of the mechanistic pathway indeed validates the synergistic effect of metal and halide ions that leads to the efficient conversion of different epoxides into cyclic carbonates. Furthermore, no significant loss in the catalytic activity of the Fe-L1 is noticed up to six cycles. The post catalytic analyses clearly indicate the robust nature of the catalyst. The developed one component bifunctional catalytic system can pave way towards transition to sustainable carbon capture and conversion.