Surface oxygenation of non-oxide boosts oxidation activity on polyoxometalate subunits: An enhanced Venus flytrap mechanism

Abstract

Typically, the interfacial wettability of catalysts, coupled with electronic modulation, is vitally controlled through surface treatments that boost catalytic performance. Simulation of the biomimetic catalytic process, for instance, a Venus Flytrap mechanism, is deemed as one of the most prospective but particularly challenging protocols to achieve efficient redox catalysis. Herein, a green oxidative desulfurization (ODS) system was readily fabricated, which constituted a modular moiety ionic liquid ([Bmim]Br) triggered PW12O40 (BHPW) anchored on oxygenated graphitic carbon nitride (o-CN). The BHPW/o-CN activates the reaction at 50 °C and is almost two times higher activity than that of BHPW/CN, combined ultrastability with handy synthetic availability for the deep oxidation of carbon–sulfur (C–S) bonds. Oxygen content serves as a descriptor for the catalytic performance. We demonstrate through mimicking CS2- and thiophene-TPD that the adsorption and pre-activation of C–S bonds on the hydrophilic CN surface are critically important for proceeding ODS reaction. Further, systematic characterization containing FT-IR, XPS, and UV–vis indicates the nature of the electron acceptor raised by the oxygen moieties for a plausible mechanism of C–S bonds and spilling to reactive centers. 1H NMR and H–D isotopic exchange analysis confirm the transfer of a proton from HPW to protonated [Bmim]– functional groups triggering the active sites for C–S bonds oxidation. Additionally, density functional calculation revealed the electronic modification of the CN properties shows conclusive activation and synergistic electron transfer mechanism for C–S. The catalyst realizes deep ODS of real diesel at 70 °C with negligible decay in successive cycles. Importantly, the extension of this protocol to other non-oxide (boron nitride) and active phases (molybdenum oxide and polyoxometalates) gives to the present widespread versatility and applicability.