Hydrogen bond donor functionalized poly(ionic liquid)s for efficient synergistic conversion of CO to cyclic carbonates

• Published in: Physical chemistry chemical physics : PCCP 2021-01, Vol.23 (3), p.25-214
• Main Authors: Gou, Haibin, Ma, Xifei, Su, Qian, Liu, Lei, Ying, Ting, Qian, Wei, Dong, Li, Cheng, Weiguo
• Format: Article
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d0cp06041k

The development of metal-free, high effective and recyclable catalysts plays a pivotal role in transforming CO 2 into high value-added products such as cyclic carbonates. In this paper, we introduced the hydrogen bond donor (HBD) groups into poly(ionic liquid)s via free radical polymerization, which successfully combined the HBD and ionic liquids (ILs) into one heterogeneous catalyst. The HBD could synergistically activate epoxides with hydroxyl functionalized ionic liquids and efficiently catalyze the cycloaddition of CO 2 into cyclic carbonates. The yield of propylene carbonate (PC) reached 94% (at 105 °C, 2 MPa CO 2 , 3 h), which far exceeded poly(ionic liquid)s without HBDs functionalization (PC yield 72%), and even approached bulk ionic liquids (PC yield 95%). Moreover, HBD-functionalized poly(ionic liquid)s (HPILs) exhibited excellent recyclability after five runs and afforded wide substrate scope. According to the experimental results, 1 H NMR spectra and density functional theory (DFT) calculations showed 2-hydroxyethyl methacrylate (HEMA) and the hydroxyl of ILs would form strong H-bonds with epoxides contributing to the ring-opening process of epoxides, and a possible HBD and nucleophilic anion synergistically catalytic mechanism was proposed. The method herein paved a brand new way for green technology and utilization of poly(ionic liquid)s. A series of heterogeneous catalysts, combined hydrogen bond donors and ionic liquids, are reported for efficient CO 2 cycloaddition with epoxides.