Coupling Waste Plastic Upgrading and CO2 Photoreduction to High-Value Chemicals by a Binuclear Re-Ru Heterogeneous Catalyst

Photocatalytically converting waste plastic to high-value chemicals is an energy-efficient and promising approach. Nonetheless, the limited photocatalytic efficiency due to the extremely low water solubility of the plastic and the excessive release of CO2 caused by overoxidation during the reaction seriously restricts its practical application. Herein, we propose a tandem process of waste Poly(ethylene terephthalate) (PET) plastic degradation and CO2 photoreduction on a chelating-ligand-anchored binuclear Re-Ru molecular heterogeneous catalyst. Specifically, waste PET plastics are depolymerized and photo-oxidized to monomers and formic acid on the molecular Ru sites, while the CO2 gas externally purged and generated in situ is photoreduced to CO with an impressive TON of 115 on the molecular Re sites. Compared with the corresponding homogeneous catalyst, the product selectivity is significantly improved from 65 to 95% in water-containing systems, and the TON is also greatly increased by nearly 19 times. Experiments and density functional theory calculations reveal that the high photocatalytic performance is attributed to the significantly enhanced light-capture capability, efficient photogenerated electron transfer between bimetallic Re-Ru sites, and substantially enhanced CO2-trapping capacity by finely regulating the chelating-ligand-based organosilica nanotube framework structure. The real-world application in nature seawater indicates that this work will provide a practical and feasible technical route for the disposal of waste plastics and mitigating carbon emissions under environmental conditions.