Metal-free POSS-based crosslinked polymers with triazole linkers as efficient single-component catalysts for CO2 conversion

Abstract

Developing efficient, metal-free catalysts for CO<inf>2</inf> utilization remains a significant challenge in green chemistry. In this work, we report two polyhedral oligomeric silsesquioxane (POSS)-based crosslinked polymers, ionic POSS-QAS-1 and neutral POSS-triprop , bearing multi-triazole linkers synthesized via copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). Comprehensive spectroscopic analyses confirm successful triazole incorporation, the presence of iodide ions (for POSS-QAS-1 ), and partial POSS cage opening forming silanol groups. The ionic POSS-QAS-1 exhibited outstanding catalytic activity for solvent- and co-catalyst-free CO<inf>2</inf>/epoxide cycloaddition, achieving > 99% conversion and 93% selectivity with epichlorohydrin (100 °C, 1 atm CO<inf>2</inf>, 24 h; TOF = 3.3 h⁻¹). Under elevated CO<inf>2</inf> pressures (10–20 atm), POSS-QAS-1 efficiently converted various terminal epoxides and can be reused for four cycles with minimal activity loss. Computational studies support an exergonic pathway involving silanol-assisted epoxide activation and iodide-mediated ring opening. These results highlight POSS-QAS-1 as an efficient, recyclable, and environmentally friendly catalyst for CO<inf>2</inf> valorization.