Ni-BDC MOF/MnO2 Composite for Highly Efficient CO2 Photoreduction to CO and CH4 Under Visible Light

Abstract

MOF-based composites with semiconductors offer synergistic effects, such as broader light absorption, improved charge carrier separation, and more active catalytic sites, all of which enhance the overall performance of the MOFs in CO₂ reduction. This study presents the development and characterization of a Ni-BDC MOF/MnO₂ composite for photocatalytic CO₂ reduction under visible light. The Ni-BDC MOF with a bandgap of 3.16 eV was integrated with γ-MnO₂, a visible light-absorbing semiconductor to improve charge separation and extend light absorption. The resulting composite exhibited a reduced bandgap of 2.7 eV, enabling efficient CO₂ reduction to CO and CH₄. Structural, optical, and electrochemical analyses confirmed the intimate interaction between Ni-BDC MOF and MnO₂, enhancing charge carrier dynamics. The optimized composite achieved high yields of CO (56.97 µmol g⁻¹) and CH₄ (23.5 µmol g⁻¹) after 6 h of irradiation, with enhanced stability and minimal electron-hole recombination. The mechanistic study revealed multiple intermediates involved in CO₂ reduction, providing insights into the pathways for CO and CH₄ formation. This work offers a sustainable approach to CO₂ conversion with potential applications in greenhouse gas mitigation and energy production.