Tailoring Layer Number of 2D Porphyrin‐Based MOFs Towards Photocoupled Electroreduction of CO₂

Abstract Inspired by the success of graphene, a series of single‐ or few‐layer 2D materials have been developed and applied in the past decade. Here, the successful preparation of monolayer and bilayer 2D porphyrin‐based metal–organic frameworks (MOFs) by a facile solvothermal method is reported. The structure transition from monolayer to bilayer drives distinct electronic properties and restructuring behaviors, which finally results in distinct catalytic pathways towards CO₂ electrocatalysis. The monolayer favors CO₂‐to‐C₂ pathway due to the restructuring of CuO₄ sites, while CO and HCOO⁻ are the major products over the bilayer. In photocoupled electrocatalysis, the Faradaic efficiency (FE) of the C₂ compounds shows a nearly fourfold increase on the monolayer than that under dark conditions (FE_C2 increases from 11.9% to 41.1% at −1.4 V). For comparison, the light field plays a negligible effect on the bilayer. The light‐induced selectivity optimization is investigated by experimental characterization and density functional theory (DFT) calculations. This work opens up a novel possibility to tune the selectivity of carbon products just by tailoring the layer number of the 2D material.