Fe−N Dual Sites in Porphyrinic Metal−Organic Frameworks for CO2-to-C2H4 Photocatalysis

Photocatalytic CO 2 reduction to C 2 H 4 remains challenging due to inefficient multielectron transfer and sluggish C−C coupling kinetics. Herein, we demonstrate that precise engineering of metal−organic framework (MOF) nodes establishes dual-functional active sites that synergistically drive C−C coupling and H 2 O activation. A hybrid photocatalyst is constructed by integrating a porphyrinic MOF (Fe-MOFBPy), featuring axially coordinated bipyridine ligands that modulate paddlewheel Fe−N nodes, with carbon nitride (CN) to form a heterojunction. Controlled linker depletion introduces defects that generate coordinatively unsaturated Fe sites and enable rational tuning of Fe−N bonding. Combined density functional theory and ab initio molecular dynamics simulations reveal that the Fe−N bond acts as a dual-functional site, where the N atom facilitates H 2 O activation and proton transfer, while the Fe center promotes *CO + *CHO coupling toward C 2 intermediates. In contrast, defective MOFs with reduced Fe−N coordination form Fe−O sites that exhibit inferior activity due to inefficient H 2 O activation. Notably, the intrinsic flexibility of the Fe−N bond lowers the kinetic barrier for H 2 O dissociation. Consequently, the catalyst achieves a C 2 H 4 production rate of 24.5 μmol g −1 h −1 with an 87.1% electron-based selectivity, outperforming analogous systems. This work provides a blueprint for designing dual-functional sites in MOFs for solar-driven C 2 H 4 synthesis.