Highly Dispersed Fe Nanoparticles on Pyridinic Nitrogen-Rich Graphitic Carbon Nitride for Efficient CO2 Conversion to Styrene Carbonate

A highly effective, atom-economical, and environmentally friendly strategy to CO2 utilisation is the solvent-free direct production of styrene carbonate (SC) from styrene oxide (SO) and CO2. This work describes a substantially effective catalytic system utilizing Fe-graphitic carbon nitride (Fe-GCN) for the selective production of SC. Fe-GCN with a small loading of around 1.68 wt.% Fe functions as an efficient heterogeneous catalyst for the CO2 cycloaddition with SO, in contrast to many conventional catalysts. It operates more effectively than other Fe-supported catalysts, with its increased activity ascribed to the synergistic interaction between Fe and N sites. A comprehensive analysis of surface functionalities and structural characteristics, including detailed XPS, kinetics, and reaction data, revealed that optimised Fe-GCN achieves an enhanced SC yield of 86% with over 99% selectivity under mild conditions (353 K, 0.2 MPa CO2) within 3 h. XPS analysis, NH3 TPD profiles, control experiments, and DFT studies confirmed the importance of pyridinic-N and Fe3+ in catalysis. Essentially, pyridinic basic sites activate CO2 to interact with SO, a process facilitated by vicinal, strongly acidic Fe3+ sites. The co-activated CO2 and SO then react to form SC. The design of Fe-GCN as a catalyst played a significant role in improving activity, with the cooperative behavior of active sites also contributing to improved conversion of both internal and terminal epoxides from different substrates.