Single Dispersion of Fe(H₂O)₂‐Based Polyoxometalate on Polymeric Carbon Nitride for Biomimetic CH₄ Photooxidation

Abstract

Direct methane conversion to value‐added oxygenates under mild conditions with in‐depth mechanism investigation has attracted wide interest. Inspired by methane monooxygenase, the K9Na2Fe(H2O)2{[γ‐SiW9O34Fe(H2O)]}2·25H2O polyoxometalate (Fe‐POM) with well‐defined Fe(H2O)2 sites is synthesized to clarify the key role of Fe species and their microenvironment towards CH4 photooxidation. The Fe‐POM can efficiently drive the conversion of CH4 to HCOOH with a yield of 1570.0 μmol gPOM−1 and 95.8% selectivity at ambient conditions, much superior to that of [Fe(H2O)SiW11O39]5− with Fe(H2O) active site, [Fe2SiW10O38(OH)]214‐ and [P8W48O184Fe16(OH)28(H2O)4]20− with multi‐nuclear 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(H2O)2 site, the HCOOH yield can be improved to 5981.3 μmol gPOM−1. Systemic investigations demonstrate that the (WO)4−Fe(H2O)2 can supply Fe = O active center for C−H activation via forming (WO)4−Fea−Ot···CH4 intermediate, similar to that for CH4 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.This article is protected by copyright. All rights reserved