Electroactive porous materials for the selective electrochemical reduction of CO₂

CO2 is a greenhouse gas (GHG) product of fuel combustion with an atmospheric concentration of over 400 ppm. Research and technologies towards its capture, storage and conversion are being developed. Porous materials play a vital role in this field, particularly conjugated microporous polymers (CMPs). CMPs combine π-conjugated structures with permanent porosity, and high thermal and chemical stability. Poly(aniline) is a highly conductive polymer that has tuneable redox properties suitable for a wide variety of applications particularly energy storage and catalysis. Poly(triphenylamine) (PTPA) CMPS are a poly(aniline)-based microporous polymer. PTPA CMPs were synthesised via Buchwald-Hartwig cross-coupling reaction. In addition, the properties of the network (e.g. porosity and band-gap) can be tuned by controlling the synthesis conditions such as temperature, solvent, reaction time, core-to-linker ratio and the addition of a salt. The validity and accuracy of the theory used to analyse the isotherms of N2 and CO2 measurements is discussed. Owing to poly(aniline)'s intrinsic redox properties, these polymers are electrocatalytically active towards CO2 reduction to fuels and feedstock at low overpotentials. CO2 electrochemical reduction (CO2ECR) was explored using a standard three-electrode two-compartment cell and a gas diffusion electrolyser (GDE) to evaluate the electrocatalytic behaviour of PTPA networks as electroactive porous materials (EPMs) in an aqueous and a gaseous environment. The results indicate the promising opportunities of CMPs for CO2ECR and its role in tackling climate change and the energy crisis.