Solid-State Electrochemical Carbon Dioxide Capture by Conductive Metal–Organic Framework Incorporating Nickel Bis(diimine) Units

This paper presents the first implementation of electrically conductive metal-organic framework (MOF) Ni₃(2,3,6,7,10,11-hexaiminotriphenylene)₂ (Ni₃(HITP)₂) integrated with nickel bis(diimine) (Ni-BDI) units for efficient solid-state electrochemical carbon dioxide (CO₂) capture. The electrochemical cell assembled using Ni₃(HITP)₂ as working electrodes can reversibly capture and release CO₂ through potential control. A high-capacity utilization of 96% and a Faraday efficiency of 98% have been achieved. The material also exhibits excellent electrochemical stability with its capacity maintained during 50 capture-release cycles and resistance to general interferences, including O₂, H₂O, NO₂, and SO₂. Capacity utilization of up to 35% is obtained at CO₂ concentrations as low as 1%. The capture of CO₂ at concentrations ranging from 1% to 100% requires exceptionally low energy consumption of only 30.5-72.4 kJ mol^-1. Studies combining spectroscopic experiments and computational approaches reveal that the CO₂ capture and release mechanism involves reversible carbamate formation on the N atom of the Ni-BDI unit in the MOF upon its one-electron redox reaction.