Searching for an efficient single-atom catalyst for benzene hydroxylation to phenol is of critical importance, but it still remains a challenge. Herein, a single-atom catalyst with unique Cu-N 2 moieties (Cu 1-N 2 /HCNS) was prepared and confirmed by HAADF-STEM and EXAFS. Turnover number (TON) over Cu 1-N 2 /HCNS (6,935) is 3.4 times of Cu 1-N 3 /HCNS (2,034) under the same reaction conditions, and both exhibit much higher phenol selectivity (close to 99%) and stability compared with Cu nanoparticles and nanoclusters. Experiments and DFT calculations reveal that atomically dispersed Cu species are active sites for benzene hydroxylation to phenol, and the Cu-N 2 is more active than Cu-N 3 owing to its much lower energy barrier concerning the activation of H 2 O 2 led by its unique coordination state of local atomic structure. We envision that this work opens a new window for modulating coordination environments of single metallic atoms in catalysis design.

Introducing single-atom metals (SAMs) is a promising strategy to improve photocatalysis of polymeric carbon nitride (PCN), but current studies are limited to loading SAMs on the surface of PCN to serve as active sites. Herein, we report an intercalation-structured hollow carbon nitride sphere composed of carbon nitride nanosheets (HCNS) with atomically dispersed Cu1N3 moieties embedded within nanosheets (Cu1@HCNS) prepared by a facile molecular assembly approach. It exhibits far superior photoredox catalysis to the pristine HCNS and the modified HCNS with Cu1N3 moieties anchored on the surface of nanosheets (Cu1/HCNS) for solar hydrogen production (3261 μmol g–1 h–1 rate with 7.1% of apparent quantum yield), in which the embedded single-atom Cu acts as a modifier to effectively modulate the electron structure and remarkably promote interfacial charge transfer of PCN rather than act as active sites to facilitate surface reaction. It can be extended to the nonoxygen coupling of benzylamine and derivants to corresponding imines, and the unexpectedly high reaction rate is achieved. The promoting effect strongly depends on the location of single-atom Cu in the PCN, and the coordination method is a very effective strategy to introduce single-atom metals in terms of the improvement in photocatalysis of PCN owing to the intensified metal–PCN interaction. This work opens up a window for further improving the photocatalytic efficiency of carbon nitride in terms of solar fuel production and clean organic synthesis.

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A mesoporous/microporous titanium silicalite with controllable pore diameter was synthesized in an easy and new route by using cetyltrimethylammonium bromide (CTAB) as a mesoporous template and tetrapropylammonium hydroxide (TPAOH) as a microporous template. This route leads to the formation of mesopores prior to the crystallization of microporous MFI topology. The porosity formation sequence makes the two types of channels, which are micropores with MFI topology and mesopores with wormlike morphology, distribute homogeneously. The pore diameter of the mesopores can be adjusted from the maximum center of 2.6 nm to that of 6.9 nm by tuning the molar ratio of CTAB to silicon from 0.125 to 0.20. The mesoporous/microporous titanium silicalite catalysts were evaluated in the epoxidation of cyclohexene, and showed excellent catalytic activities, with respect to the conventional microporous TS-1, because of the enhanced diffusion property in the mesopores and higher titanium content near the external surface of the former.