Fabrication of Swellable Organic-Inorganic Hybrid Polymers for CO2-Assisted Hydration of Propylene Epoxide

Swelling is a very common phenomenon in organic substances. However, the swelling behaviors of inorganic substances had rarely been reported. In this study, a new type of swellable organic-inorganic hybrid polymer (PIL@CHT) was designed and successfully synthesized through free-radical copolymerization of polymerizable phosphonium ionic liquid monomer and vinyl-functionalized hydrotalcite (CHT). The swelling behaviors of PIL@CHT in various solvents with a wide range of Hansen solubility parameters (delta T) were investigated, and PIL@CHT exhibited excellent swellable capacity in the solvents with delta T > 24.4 MPa1/2. The swollen state of the hybrid PIL@CHT in water presented a network structure with a diameter of approximately 8-12 mu m, and CHT particles were well dispersed to the channel of PIL. PIL@CHT was applied to catalyze the CO2- assisted hydration of propylene oxide (PO), in which a cascade reaction including the cycloaddition of CO2 and PO and the subsequent hydrolysis of propylene carbonate (PC) occurred. PIL@CHT, combining the active sites of PIL and CHT, synergistically catalyzed this cascade reaction and achieved a high yield (93.0%) and selectivity (98.2%) of 1,2-propanediol (1,2 -MPG) under a low H2O/PO ratio of 1.5/1. Moreover, the catalyst could be recycled seven times without any significant loss of catalytic activities and had good substrate generality.

Automated summary

A new type of swellable organic-inorganic hybrid polymer (PIL@CHT) was synthesized and exhibited excellent swelling capacity in solvents with a wide range of Hansen solubility parameters (delta T). The swollen state of PIL@CHT in water showed a network structure with well-dispersed CHT particles. PIL@CHT was applied as a catalyst for the CO2-assisted hydration of propylene oxide (PO) and achieved high yield and selectivity of 1,2-propanediol (1,2-MPG) under a low H2O/PO ratio.