Single Dispersion of Fe(H<sub>2</sub>O)<sub>2</sub>‐Based Polyoxometalate on Polymeric Carbon Nitride for Biomimetic CH<sub>4</sub> Photooxidation
Jing Ren, Baifan Wang, Hua‐Qing Yin, Peng Zhang, Xinhui Wang, Yangjian Quan, Shuang Yao, Tong‐Bu Lu, Zhiming Zhang
Abstract
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 K 9 Na 2 Fe(H 2 O) 2 {[γ‐SiW 9 O 34 Fe(H 2 O)]} 2 ·25H 2 O polyoxometalate (Fe‐POM) with well‐defined Fe(H 2 O) 2 sites is synthesized to clarify the key role of Fe species and their microenvironment toward CH 4 photooxidation. The Fe‐POM can efficiently drive the conversion of CH 4 to HCOOH with a yield of 1570.0 µmol g POM −1 and 95.8% selectivity at ambient conditions, much superior to that of [Fe(H 2 O)SiW 11 O 39 ] 5− with Fe(H 2 O) active site, [Fe 2 SiW 10 O 38 (OH)] 2 14− and [P 8 W 48 O 184 Fe 16 (OH) 28 (H 2 O) 4 ] 20− 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(H 2 O) 2 site, the HCOOH yield can be improved to 5981.3 µmol g POM −1 . Systemic investigations demonstrate that the (WO) 4 −Fe(H 2 O) 2 can supply Fe═O active center for C−H activation via forming (WO) 4 −Fe a −O t ···CH 4 intermediate, similar to that for CH 4 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.