Metal‐Free Photocatalytic CO<sub>2</sub> Reduction to CH<sub>4</sub> and H<sub>2</sub>O<sub>2</sub> under Non‐sacrificial Ambient Conditions
Weixin Zou, Yingyi Cheng, Yu‐Xin Ye, Xiaoqian Wei, Qing Tong, Lin Dong, Gangfeng Ouyang
Abstract
Abstract Photocatalytic CO 2 reduction to CH 4 requires photosensitizers and sacrificial agents to provide sufficient electrons and protons through metal‐based photocatalysts, and the separation of CH 4 from by‐product O 2 has poor applications. Herein, we successfully synthesize a metal‐free photocatalyst of a novel electron‐acceptor 4,5,9,10‐pyrenetetrone (PT), to our best knowledge, this is the first time that metal‐free catalyst achieves non‐sacrificial photocatalytic CO 2 to CH 4 and easily separable H 2 O 2 . This photocatalyst offers CH 4 product of 10.6 μmol ⋅ g −1 ⋅ h −1 under non‐sacrificial ambient conditions (room temperature, and only water), which is two orders of magnitude higher than that of the reported metal‐free photocatalysts. Comprehensive in situ characterizations and calculations reveal a multi‐step reaction mechanism, in which the long‐lived oxygen‐centered radical in the excited PT provides as a site for CO 2 activation, resulting in a stabilized cyclic carbonate intermediate with a lower formation energy. This key intermediate is thermodynamically crucial for the subsequent reduction to CH 4 product with the electronic selectivity of up to 90 %. The work provides fresh insights on the economic viability of photocatalytic CO 2 reduction to easily separable CH 4 in non‐sacrificial and metal‐free conditions.