Cost-effective fixation of CO2 into cyclic carbonates catalyzed by Zn bromide-based deep eutectic ionic liquid
In this work, we designed a novel thermally stable Zn bromide-based deep eutectic ionic liquid (DEIL), synthesized from tetralkylphosphonium bromide (Bu 4 PBr) and ZnBr 2 by a facile heating method. The structural changes and the physical properties of the catalyst were in-depth investigated. Among all the DEILs, ZnBr 2 ·2Bu 4 PBr showed high activity, achieved 98.2% propylene carbonate (PC) yield at a low catalyst usage (0.15 mol%), and remained good stabilities for 8 cycles. Furthermore, based on experimental results and DFT calculations, we found that Bu 4 P + cation of DEIL served as a frame charge-balanced species interacting with three possible anions of ZnBr 4 2− , ZnBr 3 − and Br − . The interaction is accompanied by a reversible pre-equilibrium in which [Bu 4 P] 2 [ZnBr 4 ] could dissociate and produce the true catalytically active species, [Bu 4 P][ZnBr 3 ] and Bu 4 PBr. Meanwhile, a possible ring-opening mechanism was proposed, in which the synergetic effect of cations and anions in the catalytic system can promote ring-opening. The significance of this study is that it provides guidance for developing metal bromide-based DEILs for carbonate synthesis.
危险品化学品经营许可证（带存储）