2D Copper Tetrahydroxyquinone Conductive Metal-Organic Framework for Selective CO₂ Electrocatalysis at Low Overpotentials.

Abstract

Metal-organic frameworks (MOFs) are promising materials for electrocatalysis; however, lack of electrical conductivity in the majority of existing MOFs limits their effective utilization in the field. Herein, an excellent catalytic activity of a 2D copper (Cu)-based conductive MOF, copper tetrahydroxyquinone (CuTHQ), is reported for aqueous CO₂ reduction reaction (CO₂ RR) at low overpotentials. It is revealed that CuTHQ nanoflakes (NFs) with an average lateral size of 140 nm exhibit a negligible overpotential of 16 mV for the activation of this reaction, a high current density of ≈173 mA cm^-2 at -0.45 V versus RHE, an average Faradaic efficiency (F.E.) of ≈91% toward CO production, and a remarkable turnover frequency as high as ≈20.82 s^-1 . In the low overpotential range, the obtained CO formation current density is more than 35 and 25 times higher compared to state-of-the-art MOF and MOF-derived catalysts, respectively. The operando Cu K-edge X-ray absorption near edge spectroscopy and density functional theory calculations reveal the existence of reduced Cu (Cu⁺ ) during CO₂ RR which reversibly returns to Cu²⁺ after the reaction. The outstanding CO₂ catalytic functionality of conductive MOFs (c-MOFs) can open a way toward high-energy-density electrochemical systems.