Confining Copper Oxide Nanoparticles within a Metal-Organic Framework for Selective Photocatalytic CO2 Reduction to Methane.

Owing to their high surface areas and structural tunability, metal-organic frameworks (MOFs) offer an ideal platform for stabilizing nanocatalysts within their well-defined pores. In this work, we report the synthesis of a zinc-based MOF, FICN-13, with a tris(pyrazolate) ligand tris[4-(1H-pyrazol-4-yl)phenyl]amine (H3TPPA). With a dual-solvent approach, copper oxide nanoparticles were deposited within the one-dimensional channels and on the external surface of FICN-13, forming an integrated MOF-CuOx heterojunction. Incorporation of CuOx nanoparticles led to a product selectivity shift from CO to CH4 in photocatalytic CO2 reduction, achieving a methane production of 56.12 μmol·g-1 and a selectivity of 62% and representing a 195% enhancement over pristine FICN-13. In situ infrared spectroscopy further revealed a stepwise hydrogenation pathway via *CO2 → *CO → *CHO → *CH3O → CH4.