Electrochemical Degradation Mechanisms in Two-Dimensional Conductive Metal-Organic Frameworks

Two-dimensional electrically conductive metal-organic frameworks (MOFs) are emerging as promising materials for electrochemical energy storage, electrocatalysis, and electrochemical separations, but their stability under extended operation remains poorly understood. Here, we systematically investigate three isostructural frameworks: Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11hexahydroxytriphenylene), Ni3(HITP)2 (HITP = 2,3,6,7,10,11-hexaiminotriphenylene), and Ni3(HHTP)2, to disentangle the roles of metal centre and ligand chemistry in governing electrochemical degradation in electrochemical double-layer capacitors. Despite their nearly identical layered hexagonal structures, the three MOFs diverge in their electrochemical durability. We find that electrochemical stability follows the order Ni3(HITP)2 > Ni3(HHTP)2 > Cu 3 (HHTP) 2 , revealing that both metal identity and ligand chemistry govern durability. Threeelectrode measurements revealed that Cu₃(HHTP)₂ degraded predominantly at the positive electrode, whereas Ni 3 (HITP) 2 showed comparable degradation at both electrodes. Ex situ analyses reveal distinct degradation pathways: Cu3(HHTP)2 undergoes ligand oxidation coupled with metal redox, involving HHTP oxidation, Cu 2+ reduction to Cu⁺, and Cu⁺ dissolution, leading to substantial Cu loss at the electrode surface. Cu3(HHTP)2 also exhibits two configuration-dependent pathways: Cu⁺ dissolution in electrolyte-rich conditions and Cu-O coordination distortion in electrolyte-limited cells. In contrast, Ni3(HITP)2 degrades more gradually through ligand-based redox activity and accompanying ligand-field distortions without metal redox, consistent with negligible Ni leaching (