文献类型：期刊文献

英文题名：Highly active bifunctional dual-arm organoboron catalysts bearing cooperative intramolecular structures for the copolymerization of CO2 and epoxides

作者：Tong, Yutao[1];Cheng, Ruihua[1,2];Dong, Huan[1];Liu, Zhen[1];Ye, Jinxing[2];Liu, Boping[3]

机构：[1]East China Univ Sci & Technol, Sch Chem Engn, Shanghai 200237, Peoples R China;[2]Guangdong Univ Technol, Sch Biomed & Pharmaceut Sci, Guangzhou 510006, Peoples R China;[3]South China Agr Univ, Coll Mat & Energy, Guangzhou 510642, Peoples R China

年份：2022

卷号：60

外文期刊名：JOURNAL OF CO2 UTILIZATION

收录：;EI(收录号：20221511957570);WOS:【SCI-EXPANDED(收录号:WOS:000789864600003)】；

基金：Acknowledgments We are grateful for the funding support from the Pujiang Talent Projects (16PJD016) .

语种：英文

外文关键词：Carbon dioxide; Copolymerization; Polycarbonate; Organoboron catalysts; Cooperative effects

摘要：A series of bifunctional hexanuclear organoboron catalysts with dual-arm structures were facile prepared via a two-step procedure in similar to 100% yields featuring six boron centers and two quaternary ammonium bromides for the epoxides/CO2 copolymerization. The boron active sites within the p-B-Hexa, m-B-Hexa, and o-B-Hexa catalysts were like two stretched "arms" presenting the cooperative intramolecular structures as para-, meta-, and ortholocations, respectively. For propylene oxide (PO)/CO2 copolymerization, the catalysts exhibited > 99% polymer selectivity under 25 - 60 degrees C. The p-B-Hexa catalyst provided the highest carbonate linkages (88%) in the poly (propylene carbonate)s while the o-B-Hexa catalyst generated much more ether linkages as 45%. The o-B-Hexa catalyst performed higher activity in cyclohexane oxide (CHO)/CO2 copolymerization, obtaining fully alternating poly(cyclohexane carbonate)s with > 99% polymer selectivity under 25 - 150 degrees C. For electron-withdrawing epichlorohydrin (ECH) monomer, the catalysts showed highly selective copolymerization (>99% polymer selectivity) and enhanced activity in comparison with tetrabomn catalysts, providing poly(chloropropylene carbonate)s with > 99% carbonate linkages under 25 - 40 degrees C. A novel bilaterally sequential copolymerization mechanism for alternating epoxide/CO2 insertion was proposed and verified by density functional theory (DFT) calculations. Bearing dual-arm intramolecular structures, the catalysts withstood the simultaneous growth of two polymer chains, achieving the enhanced activity for the copolymerization. Thus, up to seven effective boron pairs were found in the o-B-Hexa catalysts within the unique cooperative structure, leading to the PO homopolymerization in the copolymer with high ether linkages. Meanwhile, the o-B-Hexa catalyst with enough steric space exhibited higher activity than p-B-Hexa and m-B-Hexa catalysts during the copolymerization.