Tailoring 2D metal-organic frameworks for enhanced CO2 reduction efficiency through modulating conjugated ligands

Abstract

The technology of electrocatalytic reduction of CO₂ to produce hydrocarbon fuels not only alleviates energy shortages but also suppresses the greenhouse effect, demonstrating enormous potential applications. In this context, we aim to explore new reliable materials for reducing CO₂ (CO₂RR) through electrocatalysis. Hence, we investigated the performance of Cu₃(C₁₂X)₂, where X signifies organic-ligands (N₁₂H₆, N₉H₃O₃, N₉H₃S₃, N₆O₆, N₆S₆) for the CO₂RR using density functional theory (DFT). The 2D Cu₃(C₁₂X)₂ monolayers show metallic characteristics because of the presence of adequate π electron conjugation network as-well-as a constructive interaction between the metal atom, organic-ligands, and benzene-rings, with the exception of Cu₃(C₁₂N₉H₃O₃)₂, which displayed semiconducting characteristic. The catalytic activity of Cu₃(C₁₂X)₂ can be tuned by adjusting the organic-ligands' ability to facilitate interaction between the CO₂RR intermediates and the metal complex (Cu-X₄). Among all MOFs, Cu₃(C₁₂N₆S₆)₂ have excellent CO₂RR activity towards CO and formic acid. All other Cu₃(C₁₂X)₂ monolayers demonstrated dynamic CO₂RR catalytic activity as well as superior selectivity over hydrogen evolution (HER) suggesting that these materials have the potential to be useful as CO₂RR electrocatalysts. This study introduces the concept of building MOFs with favorable features to meet the specific needs of a number of research domains including catalysis, energy conversion and storage.