First Photocatalytic\nSynthesis of Cyclic Carbonates\nfrom CO<sub>2</sub> Using Bromide-Functionalized Polyoxometalate without\nAdditional Cocatalyst

Developing\nphotocatalysts with low energy consumption\nand high\nefficiency for CO<sub>2</sub> fixation without any cocatalyst is a\nhighly sought-after goal, but it still presents a significant challenge.\nHerein, aiming at enhancing the efficiency of photodriven CO<sub>2</sub> cycloaddition reactions, an imidazolium bromide ionic liquid-functionalized\npolyoxometalate photocatalyst ImBr-[Ru(C<sub>10</sub>N<sub>2</sub>H<sub>8</sub>)<sub>2</sub>]H[AsW<sub>12</sub>O<sub>40</sub>]·2H<sub>2</sub>O with Ru-based photosensitizer coordinated with ionic liquids\nvia strong coupling between the metal active site and carboxy group\nis reported. The optimized ImBr-[Ru(C<sub>10</sub>N<sub>2</sub>H<sub>8</sub>)<sub>2</sub>]H[AsW<sub>12</sub>O<sub>40</sub>]·2H<sub>2</sub>O achieves efficient photocatalytic CO<sub>2</sub> cycloaddition\nwith epoxides at ambient temperature without additional cocatalyst\nand photosensitizer, which is much higher than most reported photocatalysts\nin the presence of TBAB cocatalyst. The experimental results indicated\nthat imidazolium bromide ionic liquid facilitating the ring-opened\nreaction of epoxides, the radical mechanism, and a plausible reaction\npathway for the epoxidation step was further proposed by in situ DRIFT\nand EPR. Remarkably, this is the first report on the photoeffect of\npolyoxometalate-based catalysts with ionic liquid-functionalized molecules\nfor catalytic CO<sub>2</sub> photofixation without any cocatalyst\nand sacrificial agent.