Internal Electric Field-Regulated Dual-Site Fe-Re Supramolecular Assembly for Photocatalytic CO2 Reduction Toward Multicarbon Products.

Abstract

Photocatalytic CO2 reduction to multicarbon products remains challenging because C-C coupling is kinetically demanding and often limited by inefficient charge separation and poor control over reaction intermediates. Herein, a heterobimetallic supramolecular catalyst (Fe-Re SA) is constructed via electrostatic self-assembly between a porphyrinic FeTCPP unit and a molecular Rebpy complex. Structural and spectroscopic analyses confirm that the Fe-N4 and Re(I) carbonyl coordination environments remain preserved after assembly, while density functional theory (DFT)-supported interfacial charge redistribution induces an internal electric field that promotes directional charge transfer and suppresses carrier recombination. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reveals *CO-related and C-C coupling-related features, supporting a tandem catalytic mechanism in which the Re site catalyzes CO generation and the Fe-centered porphyrin promotes subsequent C-C coupling. As a result, Fe-Re SA exhibits enhanced photocatalytic CO2 reduction toward multicarbon products, achieving a C2H4 formation rate of 4967 µmol g-1 h-1 with a total C2 selectivity of 57.2% (C2H4 selectivity of 47.5%) among carbon-containing products. The catalyst also maintains decent activity under low CO2 concentration (3% CO2 in Ar) and under natural sunlight irradiation, highlighting its potential for practical solar-driven CO2 conversion.