Organocatalytic binary system enables high-performance alternating poly(propylene carbonate) from CO2 and propylene oxide

Poly(propylene carbonate) (PPC), a sustainable polymer derived from CO 2 , has emerged as an attractive alternative to petrochemical-based polyether polyols. Nevertheless, achieving high activity, a perfectly alternating microstructure, narrow dispersity (Đ), and excellent selectivity simultaneously in PPC synthesis has remained challenging. Herein, a binary catalyst system composed of tetrabutylammonium hydrogen sulfate or tetrabutylphosphonium hydrogen sulfate (TBAHS or TBPHS) in combination with triethylboron (Et 3 B) is reported. Density functional theory (DFT) calculations revealed that CO 2 is initially activated by the hydrogen sulfate anion to generate a carbonate intermediate, which subsequently undergoes nucleophilic attack on propylene oxide (PO) activated by Et 3 B. Under optimized conditions, the TBPHS/Et 3 B system delivered a turnover frequency (TOF) of 1051 h⁻ 1 , an average molecular weight (Mn) of 57.88 kg mol⁻ 1 , Đ = 1.67, 99 % selectivity, and perfect alternating PPC. This binary system thus provides a scalable and environmentally benign route to CO 2 utilization, establishing a compelling platform for commercial PPC production with high activity, excellent selectivity, and precise alternating microstructural control.