Single Dispersion of Fe(HO)-Based Polyoxometalate on Polymeric Carbon Nitride for Biomimetic CH Photooxidation.

Direct methane conversion to value-added oxygenates under mild conditions with in-depth mechanism investigation has attracted wide interest. Inspired by methane monooxygenase, the KNaFe(HO){[γ-SiWOFe(HO)]}·25HO polyoxometalate (Fe-POM) with well-defined Fe(HO) sites is synthesized to clarify the key role of Fe species and their microenvironment toward CH photooxidation. The Fe-POM can efficiently drive the conversion of CH to HCOOH with a yield of 1570.0 µmol g and 95.8% selectivity at ambient conditions, much superior to that of [Fe(HO)SiWO] with Fe(HO) active site, [FeSiWO(OH)] and [PWOFe(OH)(HO)] with multinuclear Fe-OH-Fe active sites. Single-dispersion of Fe-POM on polymeric carbon nitride (PCN) is facilely achieved to provide single-cluster functionalized PCN with well-defined Fe(HO) site, the HCOOH yield can be improved to 5981.3 µmol g . Systemic investigations demonstrate that the (WO)-Fe(HO) can supply Fe═O active center for C-H activation via forming (WO)-Fe-O···CH intermediate, similar to that for CH oxidation in the monooxygenase. This work highlights a promising and facile strategy for single dispersion of ≈1-2 Å metal center with precise coordination microenvironment by uniformly anchoring nanoscale molecular clusters, which provides a well-defined model for in-depth mechanism research.