Integrated Closed-Cycle Strategy for Recovery-Regeneration-Reuse of Spent Melamine Sponge-Supported Perovskites Toward Sustainable CO2 Photoreduction.

The photocatalytic conversion of CO2 into solar fuels using lead halide-perovskites is promising, yet hindered by their instability in aqueous media and environmental concerns regarding lead leaching. This work constructs an integrated MS/CsPbBr3/3DOM-Co3O4 catalytic system, where a melamine sponge (MS) serves as a porous scaffold to stabilize the perovskite in a gas-solid reaction environment, enabling efficient CO2 reduction with water vapor as a proton source. After reaction, the spent perovskite-loaded sponge can be readily collected, and an efficient closed-cycle recovery strategy combining resin-adsorption, gradient-elution, directional-deposition, and targeted-conversion is employed to reclaim lead as PbBr2, achieving a recovery efficiency of 95.01%. Crucially, the CsBr-rich DMSO solution and the purified DMSO solvent are simultaneously recovered and directly reused for perovskite resynthesis, significantly reducing reagent consumption and environmental impact. The regenerated photocatalyst maintains stable performance over five consecutive catalysis-recovery-regeneration cycles, retaining over 80% of initial production rates for CO and CH4, which demonstrates excellent sustainability and operational stability. Importantly, this strategy demonstrates broad applicability for recycling lead from diverse perovskite compositions. This work provides a comprehensive and practical strategy for the lifecycle management of lead-based photocatalysts, effectively addressing both performance and environmental challenges in CO2 photoreduction.