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Metal-decorated oxide semiconductors are overwhelming photocatalysts for nonoxidative coupling of methane (NOCM). However, the overall NOCM mechanism remains an unopened black box, which hinders the design of high-performance catalysts. Herein, we systematically studied a series of noble metal (Ag, Au, Pt, Pd, Cu, and Ni)-decorated oxides (NaTaO3, CaTiO3, LiNbO3, and TiO2) for NOCM. We proposed that the active sites for H abstraction and C–C coupling of CH4 are spatially separated. Specifically, NaTaO3 only completes the initial H abstraction of CH4 activation, while metal nanoparticles are responsible for the final C–C coupling. Noble metals dominate NOCM by significantly decreasing the energy barrier of CH4 dissociation and promoting C–C coupling. Among various metals, Ag is preferential for the weak adsorption of ·CH3 intermediates and subsequent metal-induced C–C coupling. This contributes to Ag/NaTaO3 the highest C2H6 yield of 194 μmol g–1 h–1 and stoichiometric H2 with 11.2% quantum efficiency. This work provides a molecular-level insight into the CH4 coupling mechanism on metal-decorated photocatalysts.

Heterophase junction composite semiconductors have been documented to exhibit better photocatalytic activity than the corresponding single-phase semiconductors for chemical reactions such as the hydrogen evolution and the degradation of pollutants. However, how to further improve the photocatalytic activity of these materials is a great challenge from the perspective of theory and practice. Herein, we report the synthesis of the rutile/anatase micro-heterophase junction from nanoscale anatase TiO 2 by a rapid thermal treatment followed by liquid nitrogen quenching (RQ). The RQ micro-heterophase junction sample showed excellent photocatalytic hydrogen evolution activity, which has 4−5 times higher hydrogen production rate than that of nude anatase and P25-TiO 2 , and 2 times better hydrogen production rate than the anatase/rutile TiO 2 heterophase sample with comparable Brunauer−Emmett−Teller (BET) surface area and phase composition obtained through slow thermal treatment and natural cooling (SN) process. The enhanced photocatalytic capacity of the RQ sample is attributed to the formation of a rutile/anatase micro-heterophase junction and its modification of the heterophase interface in the treatment process. Especially, the RQ-TiO 2 sample shows a stronger electron paramagnetic resonance (EPR) signal of Ti 3+ than the pristine anatase, rutile TiO 2 , and SN-TiO 2 , implying the formation of Ti 3+ ions at the interface between anatase and rutile components. This results in moving down the Fermi level of the rutile phase by 330 meV. This increases the Fermi level difference between anatase and rutile, increases the build-in electric field (BIEF) of the anatase/rutile heterophase junction, and the separation as well as the transfer of photogenerated charge carriers more effective through the rutile/anatase heterophase interface. This work provides not only a facile method for the preparation of the rutile/anatase micro-heterophase junction from anatase but also finds a pathway to regulate the BIEF with a self-doped low-valence metal ion.

A palladium-catalyzed cascade radical cyclization and carbonylation of 1,7-enynes with perfluoroalkyl iodides and alcohols has been described. This procedure provides a facile and efficient approach for the construction of 3,4-dihydroquinolin-2(1H)-one skeletons by using benzene-1,3,5-triyl triformate (TFBen) as the CO source. This method enables the incorporation of both perfluoroalkyl and carbonyl units into the 3,4-dihydroquinolin-2(1H)-one skeletons, producing a variety of 3,4-dihydroquinolin-2(1H)-one derivatives in moderate to high yields and with excellent E/Z selectivity.