Multi-Interfacial Engineering of TiO2@TPA-Pt-CuPc Heterostructures for Highly Selective Photocatalytic CO2-to-CH4 Conversion

Abstract

Photocatalytic reduction of CO2 into CH4 represents a sustainable strategy for carbon recycling, yet achieving efficient multi-electron transfer and selective C–H bond formation remains challenging. Herein, we construct a cooperative multi-interfacial photocatalytic system by integrating copper phthalocyanine (CuPc) and photodeposited Pt nanoparticles onto a TiO2@TPA hybrid. The TiO2@TPA framework, derived from MIL-125 hydrolysis, provides robust Ti–O–C linkages and intrinsic ligand-to-metal charge transfer (LMCT) channels, while CuPc extends visible-light absorption and facilitates interfacial electron delocalization and migration through its π-conjugated macrocycle. Pt nanoparticles exhibit dual functionality—as electron sinks on TiO2 for multi-electron CO2 reduction and as interfacial bridges promoting charge transfer between TiO2 and CuPc. Comprehensive spectroscopic and photoelectrochemical analyses confirm efficient carrier separation, accelerated interfacial charge transfer, and strong electronic coupling at the heterointerfaces. The optimized TiO2@TPA(15Pt,5Cu) catalyst achieves a CH4 evolution rate of 199.2 μmol·g-1·h-1 with 99.9% selectivity, markedly outperforming single-component or monometallic counterparts. In-situ FTIR spectroscopy reveals successive *COOH, *CO, *CHO, and *CH intermediates, validating the multi-step hydrogenation mechanism. This work extends LMCT-based interface engineering toward deep CO2 methanation, offering new insights for the rational design of highly efficient and selective multi-electron photocatalysts.