Noble-metal-free π-stacked metal–organic nanosheets featuring unidirectional electron transport channels for highly efficient electrocatalytic CO2 reduction

Abstract

Two-dimensional (2D) electrocatalysts are widely explored for electrocatalytic CO₂ reduction, yet disordered electron transport within these catalysts often limits performance due to elongated electron pathways and poor accessibility to catalytic sites. Here, we report a noble-metal-free 2D metal–organic electrocatalyst (MPhene) featuring unique unidirectional electron transport channels formed via long-range π–π stacking of natural phenolic bio-ligands. These ordered molecular structures facilitate highly efficient electron transport to catalytic bismuth (Bi^III)-coordinated centers, enabling highly selective CO₂ reduction to formic acid (HCOOH) with >90% selectivity across a broad potential window (−0.7 to −1.1 V vs. the reversible hydrogen electrode). Notably, MPhene achieves a peak partial current density of 115.5 mA cm⁻² for HCOOH production, representing record-high electrocatalytic activity and significantly surpassing the performance of all previously reported advanced noble-metal-free 2D electrocatalysts in neutral electrolytes. In situ Raman spectroscopy and theoretical calculations reveal the critical role of unique unidirectional electron transport channels in enhancing catalytic performance. This work introduces a novel supramolecular design strategy for controlling electron transport in noble-metal-free 2D electrocatalysts, offering new opportunities in photocatalysis, photoelectronics, and CO₂ reduction technologies.