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.