Waste-derived elastic carbon catalysts for integrated CO₂ capture and cycloaddition to cyclic carbonates

The pressing global challenge of anthropogenic CO₂ emissions, mainly driven by urban growth and industrial activity, is compounded by the ongoing environmental impacts of discarded melamine foam (MF). In response, the cycloaddition of CO₂ with epoxides to form cyclic carbonates offers a promising approach to address these issues; however, this process has been limited by the low reactivity of CO₂ and the shortcomings of current catalysts. This study presents a new "waste-treating-waste" approach in which discarded MF is transformed into a strong, compressible carbon sponge. Notably, the optimized PEI-Zn-30-0.5 catalyst, synthesized by integrating carbon sponge, polyethyleneimine, zinc acetate, and 1-ethyl-3-methylimidazolium bromide, exhibits a remarkable 98% yield and 99% selectivity for propylene carbonate. This excellent performance occurs under mild, co-catalyst- and solvent-free conditions. Additionally, the new catalytic system performs effectively with a wide range of epoxide substrates. The improved mass transfer and better access to active sites result from the hierarchical porosity and uniform nanolayer of the catalyst. Overall, this research provides a practical, sustainable way to recycle MF waste and to use CO₂ efficiently, thereby greatly supporting efforts toward global carbon neutrality.