Evaluation of Influencing Factors in Tetravalent Uranium Complex-Mediated CO2 Functionalization by Density Functional Theory

Novel Styrene-Based Polyamine Sorbent for Efficient Selective Separation of Molybdenum

Tungsten (W) and molybdenum (Mo) are important strategic resources but the two coexist in both primary ore and waste. Before a single metal product is obtained, it is often necessary to separate the two. In this work, we reported two new polyamine resins (D301@PA and D301@TA), which can be obtained by an assembled amine (primary amine or tertiary amine) and traditional D301 resin by the dipping method. Then, the sorption experiments with the amine resins were carried out, and the selectivity and sorption capacity of the two new polyamine resins for MoS₄ ^2- have been significantly improved. Among them, D301@TA showed the highest sorption capacity of 414 mg·g^-1 and a separation factor of 108. Finally, the sorption mechanism can be inferred through scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, and X-ray photoemission spectroscopy (XPS); the Cl^- ions in the amine resin and the MoS₄ ^2- ions were subjected to ion exchange. This work provides a green and efficient approach for separating tungsten and molybdenum.

CO2 Cleavage Reaction Driven by Alkylidyne Complexes of Group 6 Metals and Uranium: A Density Functional Theory Study on Energetics, Reaction Mechanism, and Structural/Bonding Properties

Designing novel catalysts is essential for the efficient conversion of metal alkylidyne into metal oxo ketene complexes in the presence of CO₂, which to some extent resolves the environmental concerns of the ever-increasing carbon emission. In this regard, a series of metal alkylidyne complexes, [b-ONO]M≡CCH₃(THF)₂ ([b-ONO] = {(C₆H₄[C(CF₃)₂O])₂N}^3-; M = Cr, Mo, W, and U), have been comprehensively studied by relativistic density functional theory calculations. The calculated thermodynamics and kinetics unravel that the tungsten complex is capable of catalyzing the CO₂ cleavage reaction, agreeing with the experimental findings for its analogue. Interestingly, the uranium complex shows superior catalytic performance because of the associated considerably lower energy barrier and larger reaction rate constant. The M≡C moiety in the complexes turns out to be the active site for the [2 + 2] cyclic addition. In contrast, complexes of Cr and Mo could not offer good catalytic performance. Along the reaction coordinate, the M-C (M = Cr, Mo, W, and U) bond regularly transforms from triple to double to single bonds; concomitantly, the newly formed M-O in the product is identified to have a triple-bond character. The catalytic reactions have been extensively explained and addressed by geometric/electronic structures and bonding analyses.