Separation of TcO4– by a cationic covalent organic framework is achieved for the first time, showing advantages of extremely fast sorption kinetics, ultrahigh uptake capacity, good anion-exchange selectivity, and excellent radiation resistance.
The design and synthesis of uranium sorbent materials with high uptake efficiency,c apacity and selectivity, as well as excellent hydrolytic stability and radiation resistance remains ac hallenge.H erein, ap olyoxometalate (POM)organic framework material (SCU-19)w ith ar are inclined polycatenation structure was designed, synthesized through as olvothermal method, and tested for uranium separation. Under dark conditions, SCU-19 can efficiently capture uranium through ligand complexation using its exposed oxoatoms and partial chemical reduction from U VI to U IV by the lowvalent Mo atoms in the POM. An additional U VI photocatalytic reduction mechanism can occur under visible light irradiation, leading to ah igher uranium removal without saturation and faster sorption kinetics. SCU-19 is the only uranium sorbent material with three distinct sorption mechanisms,a sf urther demonstrated by X-ray photoelectron spectroscopy(XPS) and X-ray absorption near edge structure (XANES) analysis.
Enrichment of uranyl from seawater is crucial for the sustainable development of nuclear energy, but current uranium extraction technology suffers from multiple drawbacks of low sorption efficiency, slow uptake kinetics, or poor extraction selectivity. Herein, we prepared the first example of amidoxime appended metal-organic framework UiO-66-AO by a postsynthetic modification method for rapid and efficient extraction of uranium from seawater. UiO-66-AO can remove 94.8% of uranyl ion from Bohai seawater within 120 min and 99% of uranyl ion from Bohai seawater containing extra 500 ppb uranium within 10 min. The uranyl sorption capacity in a real seawater sample was determined to be 2.68 mg/g. In addition, the recyclability of the UiO-66-AO framework was demonstrated for at least three adsorption/desorption cycles. The origin for the superior sorption capability was further probed by extended X-ray absorption fine structure (EXAFS) analysis on the uranium-sorbed sample, suggesting multiple amidoxime ligands are able to chelate uranyl(VI) ions, forming a hexagonal bipyramid coordination geometry.
The catalytic oxidation of alkenes to α-diketones is unprecedented. A new oxidation of alkenes, catalyzed by a ruthenium complex, which allows an efficient route to α-diketones using TBHP as an oxidant is described. This methodology is highly functional group tolerant, is practically convenient, requires no additional ligand, and operates under mild conditions with short reaction times. Based upon experimental observations, a plausible mechanism is proposed.
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