A combined computational and experimental study on the tetrabutylammonium bromide supported organometallic/triethylboron catalytic system for the copolymerization of carbon dioxide and propylene oxide

The ring opening copolymerization (ROCOP) of propylene oxide (PO) and carbon dioxide (CO 2 ) provides a sustainable route to poly (propylene carbonate) (PPC); however, achieving high catalytic activity, selectivity, and fully alternating copolymer remains a significant challenge in ROCOP. Herein, a ternary catalytic system, [(MO t Bu/TBAB) Et 3 B], is reported, in which metal tert -butoxide (MO t Bu), tetrabutylammonium bromide (TBAB), and triethylboron (Et 3 B) act synergistically to enhance catalytic performance. Density functional theory (DFT) calculations reveal that CO 2 is activated via dual interactions with metal cation (M + ) and tert -butoxide anion (O t Bu⁻), while Et 3 B promotes PO activation. These cooperative effects polarize the monomers and substantially lower the kinetic barriers for both PO ring opening and CO 2 insertion. Furthermore, TBAB functions as a phase-transfer agent and enhances CO 2 solubility in the reaction medium. Experimentally, this ternary system enables highly alternating copolymerization, delivering PPC with 99% selectivity, high average molecular weight (Mn = 47.72 kg mol ̶ 1 ), narrow dispersity (Đ = 1.03) and turnover frequency (TOF) = 90.6 h⁻ 1 . Notably, the KO t Bu-based catalyst exhibits superior performance compared to its NaO t Bu analogue. Overall, this work advances mechanistic understanding while establishing an efficient and selective catalytic platform for the sustainable production of PPC.