Sustainable repurpose of waste melamine foam into bifunctional catalysts for efficient CO2 capture and conversion

Global climate change has driven the scientific community to improve the utilization of a critical C1 resource carbon dioxide (CO 2 ) through carbon capture utilization (CCU) technology. The cycloaddition of CO 2 with epoxides provides perfect atom economy and economic feasibility to produce versatile cyclic carbonates used in various industries. However, the stable nature of CO 2 and epoxides requires highly active catalysts. In this work, the repurpose of nitrogenous waste melamine foams (MF) as high-performance catalysts for the cycloaddition of CO 2 were explored. The pyrolyzed MF were modified with Cu to prepare a series of acid-base bifunctional porous catalysts (MFC-X-Cu). The results demonstrate that the acid-base synergy of the MFC-X-Cu catalysts increases the efficiency of the cycloaddition of various epoxides, yielding target products at 96-99% under mild conditions. Moreover, the characterization results revealed that the superior performance of MFC-X-Cu stems from its hollow structure and acid-base synergy, which are derived from nitrogen species in the repurposed MF and the post-modified copper component. The catalyst maintained consistent catalytic efficiency over five cycles, highlighting its strong recyclability. This work presents an eco-friendly and sustainable approach towards carbon neutrality by utilizing modified waste materials for CO 2 conversion into high-value chemicals.