Mechanical pressure-mediated Pd active sites formation in NaY zeolite catalysts for indirect oxidative carbonylation of methanol to dimethyl carbonate

The Cooperation of Pd center and Lewis Acid Sites to Achieve High Selectivity Towards Kinetic Carbonate Product for Oxidative Carbonylation Reaction

Dimethyl carbonate and dimethyl oxalate are competitive products of the carbonylation reaction of methyl nitrite (MN) under Pd-based catalysts. The chemo-selectivity is influenced not just by the thermodynamic constraints of reaction conditions but also by the electronic structures of catalysts. Lewis acid sites are extensively employed to modulate the electronic structures of Pd active sites for kinetic carbonate production, but their precise role remains unclear. Herein, we employed a combination of reaction kinetic, in situ DRIFTS experiments and DFT calculation, unveiling the indispensable role of Lewis acid sites in activating MN and facilitating the transfer of *OCH3 species, which is the key to obtain the kinetic carbonate outcome. The molecular understanding reveals the cooperation of Pd center and Lewis acid sites in directing selectivity towards carbonate product, which enables the rational design of higher-performance catalysts.

Enhanced Fenton-like process via interfacial electron donating of pollutants over in situ Cobalt-doped graphitic carbon nitride

The heterogeneous Fenton process suffers from low efficiency because of the low electron transfer cycle rate of Fe³⁺/Fe²⁺, which often consumes enormous amounts of hydrogen peroxide (H₂O₂) or other energy. Herein, we report a novel Co-based Fenton-like catalyst (in-situ-Co-g-C₃N₄) synthesized via the surface complexation method, in which Co species were modified in situ into the framework of the graphitic carbon nitride (g-C₃N₄) substrate through C-O-Co chemical bonding. The catalyst exhibited higher Fenton-like catalytic activity than pure g-C₃N₄ in the degradation of various pollutants under neutral conditions, as evidenced by the approximately 150-fold higher Fenton-like reaction rate constant of in-situ-Co-g-C₃N₄ than that of g-C₃N₄. Density functional theory (DFT) calculations and a series of experimental and characterization analyses revealed the interfacial reaction mechanism between H₂O₂, pollutants and in-situ-Co-g-C₃N₄. During the Fenton-like reaction, the electron-poor C center on the aromatic ring of g-C₃N₄ could capture the electrons deprived from pollutants, and subsequently deliver them to around the electron-rich Co center to efficiently reduce H₂O₂ to hydroxyl radicals (^•OH), enabling H₂O₂ to be used efficiently for the degradation of pollutants. This study provides a strategy for improving Fenton-like degradation efficiency by effectively utilizing the energy of organic pollutants.