Photothermal CO2 conversion to cyclic carbonate over titanium-substituted polyoxometalate within covalent organic frameworks

Abstract

The fixation of CO₂ with epoxides offers a promising approach for the converting CO₂ into valuable chemicals, particularly when driven by the synergistic combination of solar energy and thermal processes. Consequently, the development of innovative and efficient catalysts for photothermal CO₂ cycloaddition under visible light irradiation is of critical importance. In this study, we encapsulated titanium-substituted polyoxometalates ([PTi₂W₁₀O₄₀]⁷⁻, abbreviated as PTi₂W₁₀) within covalent organic frameworks (COFs), specifically EB-TFP. The resulting PTi₂W₁₀@EB-TFP composite exhibits outstanding performance in photothermal catalytic CO₂ cycloaddition, offering a product yield of 98.62 %, which significantly exceeds those obtained with the individual components PTi₂W₁₀ (61.39 %) and EB-TFP (50.34 %). In-situ experiments and theoretical calculations indicate that the superior catalytic performance arises from the photothermal catalytic pathway, rather than a synergistic interaction between photocatalytic and thermal pathways. Notably, photogenerated electrons are transferred to PTi₂W₁₀, promoting the activation of the epoxide, while the electron-deficient EB-TFP facilitates CO₂ activation. This work exemplifies the utilization of polyoxometalates as photothermal catalysts for CO₂ cycloaddition, offering a sustainable and efficient strategy to chemical conversion.