Designing molecular and two-dimensional metalloporphyrin catalysts for the electrochemical CO2 reduction reaction

Abstract

The electrochemical CO₂ reduction reaction (eCO₂R) is an important route toward the sustainable conversion of CO₂ to value-added chemicals. However, developing efficient catalysts with high selectivity and stability remains challenging. Metalloporphyrins (M–PORs) represent an attractive class of molecular catalysts because their structural framework offers a unique combination of tunability of the peripheral ligands, flexibility of the metal centre, and versatility of the oxidation state of the metal. These properties can be exploited to tailor the catalytic properties of M–PORs for the eCO₂R. Here, we present a comprehensive computational study using density functional theory to systematically explore M–POR catalysts with varying metal centers (Ni, Fe, Cu, Co), oxidation states, and anchoring ligands, aimed at enhancing the selective production of the C₁ products (carbon monoxide and formic acid). Thermodynamic and electrochemical stability analyses revealed neutral M–PORs to be significantly more stable than their charged counterparts, providing crucial guidelines for catalyst design. A mechanistic analysis of reaction pathways—proton-coupled electron transfer (PCET) versus sequential proton and electron transfer (PT–ET)—identified PCET as highly favourable, with predominant selectivity towards formic acid. This study identifies Fe–POR as the one showing superior catalytic performance. Importantly, integrating these optimal molecular catalysts into two-dimensional (2D) carbonaceous frameworks led to further enhancement of catalytic performance, identifying 2D Fe–POR as a highly promising material for selective C₁ product formation, thus providing a rational framework for designing effective molecular-to-framework electrocatalysts for the eCO₂R.