Semiconducting Metal–Organic Frameworks Decorated with Spatially Separated Dual Cocatalysts for Efficient Uranium(VI) Photoreduction

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 (MnOx/UiO‐66/Ti3C2Tx) with spatially separated dual cocatalysts (MnOx nanoparticles and Ti3C2Tx MXene nanosheets) is successfully developed for efficient U(VI) photoreduction without sacrificial agents. As co‐catalysts, MnOx nanoparticles favor the trapping of holes, while Ti3C2Tx 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 MnOx/UiO‐66/Ti3C2Tx to remove U(VI). Impressively, the U(VI) removal ratio via MnOx/UiO‐66/Ti3C2Tx reaches to 98.4% in the U(VI) solution after 60 min, with a photoreaction rate constant of 0.0948 min−1. Moreover, MnOx/UiO‐66/Ti3C2Tx 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 Ti3C2Tx MXene to reduce U(VI) and generate ·O2–, further leading to a stable crystal phase of (UO2)O2·2H2O. Furthermore, the photogenerated holes are extracted by MnOx nanoparticles in MnOx/UiO‐66/Ti3C2Tx to oxidize water.

Sulfur edge in molybdenum disulfide nanosheets achieves efficient uranium binding and electrocatalytic extraction in seawater

“…17–19 Thanks to the efforts from many research groups, various adsorbents with binding sites for uranium have been developed, such as amidoxime functionalized groups, polyphenols and phosphate groups. 20–23 Despite these advancements, the sluggish kinetics hindered the practical application of the adsorption method for uranium extraction in seawater. 24–26…”

MXene-Derived 3D Defect-Rich TiO2@Reduced Graphene Oxide Aerogel with Ultrafast Carrier Separation for Photo-Assisted Uranium Extraction: A Combined Batch, X-ray Absorption Spectroscopy, and Density Functional Theory Calculations

“…Compared with existing absorption materials, TiO 2 (M)@RGO aerogel exhibited good uranium removal ability (Table S1). ,− Based on the above analysis, we believe that the TiO 2 (M)@RGO aerogel is a promising photocatalyst candidate for U­(VI) extraction.…”

Electrocatalytic Removal of Low-Concentration Uranium Using TiO2 Nanotube Arrays/Ti Mesh Electrodes

“…In the past 2 decades, a variety of methods have been used to remove uranium from water, including adsorption, bio-reduction, electrocoagulation, photocatalytic reduction, − and photoelectrochemical reduction. , However, these methods were mainly used for the removal of high concentrations of uranium, and few studies have effectively removed the relatively low concentrations (less than 1.5 μM) of calcium–uranyl–carbonate complexes in groundwater. Recently, a promising electroreduction method has been developed to remove and recover both uranyl–carbonate complexes and calcium–uranyl–carbonate complexes from groundwater .…”