Ionic quaternary ammonium-triazole polymers as efficient single-component catalysts for CO2 conversion

Abstract

Ionic organic polymers with halide counterions have been investigated as effective and reusable single-component, heterogeneous catalysts for the cycloaddition of CO₂ and epoxides to form cyclic carbonates. In this study, we synthesized three new ionic polymers featuring quaternary ammonium-triazole functional groups with iodide counterions. Copper-catalyzed azide-alkyne cycloaddition (CuAAC) between tetrapropargylammonium bromide and various diazide compounds (N₃–Ar–N₃), where Ar represents 1,4-xylene, 1,5-naphthalene, and 4,4′-phenylbenzamide followed by halide exchange, afforded the organic polymers QAP1–3, respectively. The formation of triazole moieties and the disappearance of azide functional groups were confirmed by ¹³C CP/MAS NMR and FT-IR spectroscopy, respectively. CO₂ sorption studies showed reduced adsorption capacities compared to neutral amine analogs. The xylene-linked polymer (QAP1) exhibited the highest catalytic efficiency for CO₂/epoxide cycloaddition, achieving high conversion and selectivity under 10 atm CO₂ at 120 °C. Reusability study showed that QAP1 could be reused for four cycles with minimal loss in activity, though some thermal decomposition of quaternary ammonium groups was observed in solution.