Life Cycle Assessment of a Layered Metal-Organic Framework for Supercapacitor Applications

Abstract

Conductive layered metal-organic frameworks (MOFs) offer potential applications both as model research materials to study the electrode behaviour of fast-charging energy storage devices, and as an alternative electrode material in commercial supercapacitors. MOFs such as copper(II) 2,3,6,7,10,11-hexahydroxytriphenylene, Cu3(HHTP)2, have recently demonstrated competitive capacitive performance in supercapacitors, but their environmental implications are currently unknown. In this work, we perform a preliminary cradle-to-gate life cycle assessment to estimate the environmental impacts of lab-scale Cu3(HHTP)2 production and compare it to a benchmark activated carbon system. The environmental impacts of Cu3(HHTP)2 are found to be three to four orders of magnitude higher than activated carbon across all indicators. Hotspot and sensitivity analysis identifies solvent washing and linker production as key drivers and shows that modifying these steps could enable up to a two order of magnitude reduction in environmental impacts. These results suggest that finding new solvent-free methods for greener synthesis of conductive layered MOFs and significant improvements in capacitive performance relative to benchmark systems will be needed to enable sustainable application of these materials in commercial supercapacitor devices.