Demonstrating Electrochemical CO2 Capture with Redox-Active Metal-Organic Frameworks

Abstract

Addressing climate change calls for action to control CO2 pollution. Direct air capture offers a solution to this challenge. Making carbon capture competitive with alternatives, such as forestation and mineralisation, requires fundamentally novel approaches and ideas. One such approach is electrosorption, which is currently limited by the availability of suitable electrosorbents. In this work, we introduce copper-2,3,6,7,10,11-hexahydroxytriphenylene (Cu₃(HHTP)₂) metal-organic framework (MOF) that can act as electrosorbent for CO₂ capture, thereby expanding the palette of materials that can be used for this process. Cu₃(HHTP)₂ is the first MOF to switch its ability to capture and release CO₂ in aqueous electrolytes. By using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge (GCD) analysis, and differential electrochemical mass spectrometry (DEMS), we demonstrate reversible CO₂ electrosorption. Based on density functional theory (DFT) calculations, we provide atomistic insights into the mechanism of electrosorption and conclude that efficient CO₂ capture is facilitated by a combination of redox-active copper atom and aromatic HHTP ligand within Cu₃(HHTP)₂. By showcasing the applicability of Cu₃(HHTP)₂ – with a CO₂ capacity of 2 mmol g⁻¹ and an adsorption enthalpy of −20 kJ mol⁻¹, this study encourages further exploration of conductive redox-active MOFs in the search for superior CO₂ electrosorbents.