An ammonium rich pillararene macrocycle as a heterogeneous catalyst for cyclic carbonate synthesis†

The development of efficient catalysts for the cycloaddition of CO₂ with epoxides to produce cyclic carbonates (CCs) under mild reaction conditions remains a highly attractive research area. This study presents a trimethyl ammonium-rich pillar[5]arene (N(Me)₃⁺-P5) macrocycle as a promising heterogeneous catalyst for this reaction. The catalyst design ensures a complementary dual-function mechanism to facilitate the catalytic process. The ammonium groups activate the epoxides, and the bromide ions act as nucleophiles to initiate the ring opening. Optimized reaction conditions using 0.7 mol% catalyst loading and a CO₂ balloon at 80 °C, resulted in high CC yields, particularly with sterically unhindered epoxides. Furthermore, N(Me)₃⁺-P5 can be reused for at least five catalytic cycles, demonstrating its potential for sustainable applications.