Modulation of NH2‐UiO‐66 Based MOFs for Gas Phase CO2 Photocatalytic Reduction

This study addresses the dual challenges of the greenhouse effect and energy crisis through the direct capture and conversion of CO₂ using Metal-Organic Frameworks (MOFs). By synthesizing defective NH₂-UiO-66 MOFs and combining them with TiO₂ and gold nanoparticles, a ternary photocatalyst that significantly enhances CO₂ adsorption and CH₄ production, achieving a six-fold increase in photocatalytic activity compared to a TiO₂/Au reference catalyst is developed.

Abstract

To solve both the greenhouse effect and energy crisis issues, direct capture and conversion of CO₂ appears as a promising contribution. Artificial photosynthesis is an encouraging and very attractive complementary way to convert CO₂ into high-value-added chemicals. Nevertheless, efficient CO₂ conversion remains challenging, mainly due to the poor CO₂ adsorption_, the high activation energy required to break C═O bonds, and the slow dynamics of charge carriers in light-harvesting materials. In recent years, some Metal-organic frameworks (MOFs) have emerged in the photocatalysis field, especially due to their huge CO₂ adsorption capability and light-harvesting properties behavior. In this study, a series of defective NH₂-UiO-66 MOF materials, using formic acid (FA) is synthesized as a modulating agent. Then, a series of binary (MOF/TiO₂) catalysts is obtained by varying the defective MOFs content, followed by further deposition of gold (Au) nanoparticles (NPs) to result in three-component MOF/TiO₂/Au composites. These composites are assessed for gas-phase CO₂ photoreduction in the presence of water vapor as the only reducing agent. This hybrid ternary photocatalyst not only increases CO₂ adsorption but also promotes CH₄ formation. Among these resulting MOF/TiO₂/Au samples, the optimized photocatalytic activity results in a mean production rate of 17.2 µmol.h⁻¹.g⁻¹ _catalyst of CH₄, which is 6-fold higher than the one observed for the reference TiO₂/Au photocatalyst.