Semiconducting Metal–Organic Frameworks Decorated with Spatially Separated Dual Cocatalysts for Efficient Uranium(VI) Photoreduction
Kaifu Yu, Li Tang, Xin Cao, Zhenghong Guo, Yang Zhang, Nan Li, Changxue Dong, Xiang Gong, Tao Chen, Rong He, Wenkun Zhu
Abstract
Abstract Reduction of soluble hexavalent uranium (U(VI)) to sparingly soluble tetravalent uranium (U(IV)) with semiconductor photocatalysts is recognized as a novel, green, and simple U‐extraction method. Furthermore, effective charge separation and utilization are critical factors to achieve high‐efficiency U(VI) photoreduction. Herein, a UiO‐66‐based heterostructured photocatalyst (MnO x /UiO‐66/Ti 3 C 2 T x ) with spatially separated dual cocatalysts (MnO x nanoparticles and Ti 3 C 2 T x MXene nanosheets) is successfully developed for efficient U(VI) photoreduction without sacrificial agents. As co‐catalysts, MnO x nanoparticles favor the trapping of holes, while Ti 3 C 2 T x MXene nanosheets tend to collect electrons. Consequently, the photogenerated holes and electrons flow into and out of the photocatalyst, respectively, achieving efficient charge separation required by MnO x /UiO‐66/Ti 3 C 2 T x to remove U(VI). Impressively, the U(VI) removal ratio via MnO x /UiO‐66/Ti 3 C 2 T x reaches to 98.4% in the U(VI) solution after 60 min, with a photoreaction rate constant of 0.0948 min −1 . Moreover, MnO x /UiO‐66/Ti 3 C 2 T x exhibits brilliant U(VI) extraction capacity in various U(VI) wastewater and U(VI)‐spiked real seawater. Further mechanistic studies indicates that the photogenerated electrons are transferred from the conduction band of UiO‐66 to Ti 3 C 2 T x MXene to reduce U(VI) and generate ·O 2 – , further leading to a stable crystal phase of (UO 2 )O 2 ·2H 2 O. Furthermore, the photogenerated holes are extracted by MnO x nanoparticles in MnO x /UiO‐66/Ti 3 C 2 T x to oxidize water.