Light-Assisted CO2 Hydrogenation over Pd3 Cu@UiO-66 Promoted by Active Sites in Close Proximity

Abstract

CO₂ hydrogenation to methanol has attracted great interest while suffering from low conversion and high energy input. Herein, tiny Pd₃ Cu nanoparticles are confined into a metal-organic framework (MOF), UiO-66, to afford Pd₃ Cu@UiO-66 for CO₂ hydrogenation. Remarkably, it achieves a methanol production rate of 340 μmol g^-1 h^-1 at 200 °C and 1.25 MPa under light irradiation, far surpassing that in the dark. The photo-generated electron transfer from the MOF to antibonding orbitals of CO₂ * promotes CO₂ activation and HCOO* formation. In addition, the Pd₃ Cu microenvironment plays a critical role in CO₂ hydrogenation. In contrast to the MOF-supported Pd₃ Cu (Pd₃ Cu/UiO-66), the Pd₃ Cu@UiO-66 exhibits a much higher methanol production rate due to the close proximity between CO₂ and H₂ activation sites, which greatly facilitates their interaction and conversion. This work provides a new avenue to the integration of solar and thermal energy for efficient CO₂ hydrogenation under moderate conditions.

Keywords: heterogeneous catalysis; hydrogenation; metal-organic frameworks; microenvironment modulation.