Given society’s reliance on fossil fuels, atmospheric carbon dioxide removal or negative emission technologies are crucial to keep below the critical temperature rise threshold of 1.5 °C reported in the latest Intergovernmental Panel on Climate Change (IPCC). The energy efficient CO2 capture mechanism of moisture (humidity) swing has shown great potential in being utilised for atmospheric CO2 capture. In this work, novel quaternary ammonium functionalized poly(arylene ether sulfones) with HCO3- counterions are synthesized to reversibly capture and release atmospheric levels of CO2 in dry and humid environments, respectively. High molecular weight allyl modified poly(arylene ether sulfone) copolymer (PAES-co-APAES) are initially synthesized through step growth polymerization and quaternary ammonium groups are added to the backbone through post-polymerization functionalization to make PAES(25)-co-QAPAES(75)[HCO3-] random copolymers. Size exclusion chromatography (SEC) is utilised to measure the molecular weight of the novel polymers and the chemical structure is analyzed through nuclear magnetic resonance (1H NMR) spectroscopy. Polymer with number average molecular weight (Mn) of 89.2 KDa and dispersity of 2.9 is synthesized. Differential scanning calorimetry (DSC) confirmed amorphous morphology with non-phase separated and randomly dispersed polymer segment with a single glass transition temperature (Tg) of 112 °C. Thermogravimetric analysis (TGA) showed good thermal stability with 5% degradation temperature (Td5%) of 256 °C. The polymers show stable CO2 capture and release response with changes in humidity for six consecutive cycles.

Novel quaternary ammonium functionalized poly(arylene ether sulfone) copolymers for direct air capture

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