Ting Zhang

Developing single-atom catalysts with porous micro-/nanostructures for high active-site accessibility is of great significance but still remains a challenge. Herein, we for the first time report a novel template-free preassembly strategy to fabricate porous hollow graphitic carbonitride spheres with single Cu atoms mounted via thermal polymerization of supramolecular preassemblies composed of a melamine–Cu complex and cyanuric acid. Atomically dispersed Cu–N3 moieties were unambiguously confirmed by spherical aberration correction electron microscopy and extended X-ray absorption fine structure spectroscopy. More importantly, this material exhibits outstanding catalytic performance for selective oxidation of benzene to phenol at room temperature, especially showing phenol selectivity (90.6 vs 64.2%) and stability much higher than those of the supported Cu nanoparticles alone, originating from the isolated unique Cu–N3 sites in the porous hollow structure. An 86% conversion of benzene, with an unexpectedly high phenol selectivity of 96.7% at 60 °C for 12 h, has been achieved, suggesting a great potential for practical applications. This work paves a new way to fabricate a variety of single-atom catalysts with diverse graphitic carbonitride architectures.

Abstract Developing highly efficient catalyst for selective oxidation of benzene to phenol (SOBP) with low H 2 O 2 consumption is highly desirable for practical application, but challenge remains. Herein, we report unique single-atom Cu 1 -N 1 O 2 coordination-structure on N/C material (Cu-N 1 O 2 SA/CN), prepared by water molecule-mediated pre-assembly-pyrolysis method, can efficiently boost SOBP reaction at a 2:1 of low H 2 O 2 /benzene molar ratio, showing 83.7% of high benzene conversion with 98.1% of phenol selectivity. The Cu 1 -N 1 O 2 sites can provide a preponderant reaction pathway for SOBP reaction with less steps and lower energy barrier. As a result, it shows an unexpectedly higher turnover frequency (435 h −1 ) than that of Cu 1 -N 2 (190 h −1 ), Cu 1 -N 3 (90 h −1 ) and Cu nanoparticle (58 h −1 ) catalysts, respectively. This work provides a facile and efficient method for regulating the electron configuration of single-atom catalyst and generates a highly active and selective non-precious metal catalyst for industrial production of phenol through selective oxidation of benzene.

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.

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.