Demonstrating electrochemical CO 2 capture on redox-active metal–organic frameworks

Abstract

We report Cu 3 (HHTP) 2 as the first MOF enabling reversible CO 2 electrosorption from air and water. Measurements and calculations reveal cooperative Cu–ligand redox sites delivering 2 mmol g −1 capacity. Addressing climate change calls for action to control CO 2 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 a copper-2,3,6,7,10,11-hexahydroxytriphenylene (Cu 3 (HHTP) 2 ) metal–organic framework (MOF) that can act as an electrosorbent for CO 2 capture, thereby expanding the palette of materials that can be used for this process. Cu 3 (HHTP) 2 is the first MOF to switch its ability to capture and release CO 2 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 CO 2 electrosorption. Based on density functional theory (DFT) calculations, we provide atomistic insights into the mechanism of electrosorption and conclude that efficient CO 2 capture is facilitated by a combination of redox-active copper atoms and aromatic HHTP ligands within Cu 3 (HHTP) 2 . By showcasing the applicability of Cu 3 (HHTP) 2 – with a CO 2 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 CO 2 electrosorbents.