Controlled Assembly of Ru-Containing Polyoxometalates for Photocatalytic Activity of the Primary Amine Coupling Reaction

Abstract

Three Ru-induced structural interconversion polyoxometalates (POMs), Na 13 H 5 [Ru 4 (H 2 O) 2 (Cl) 2 (WO 2 ) 4 (AsW 9 O 33 ) 4 ]• 43H 2 O (1), K 5 Na 9 H 8 [Ru 2 (WO 2 ) 4 (AsW 9 O 33 ) 4 ]•50H 2 O (2), and KNa 13 H 14 [(WO 2 ) 4 (AsW 9 O 33 ) 4 ]•34H 2 O (3), were successfully synthesized and thoroughly characterized. Interconversion of structures was accomplished by changing the number of active sites for compounds 1− 3. All three compounds contain one {As 4 W 40 O 140 } unit, showing similar structural characteristics except for the active center number (Ru).Interestingly, compound 1 [turnover number (TON)= 486; turnover frequency (TOF)= 20 h −1 ] showed highly efficient photocatalysis in achieving oxidative coupling of primary amines. Compound 2 (TON = 406, TOF = 17 h −1 ) was also found to promote the oxidative coupling with relatively poor efficiency; however, compound 3 (TON = 178; TOF = 7.4 h −1 ) had no obvious contribution to the coupling reaction system, and a chain of evidence indicates that the catalytic performances are strongly dependent on element contents of active sites. Furthermore, the Ru-containing POM-based photocatalysts are conveniently recyclable and reusable during the photocatalytic processes. This study demonstrates the possibility of tuning the catalytic efficiency and stability of POM-based photocatalysts by well designing and controlling their structures. The possible reaction mechanism for the photocatalysis synthesis of imine product is also proposed based on experimental studies.

Controlled Assembly of a Dawson-like Antimoniotungstate-Supported Trefoil-type Trimer with Good Proton Conductivity Performance

“…Also, the formation of compound 1 also provides a feasible synthetic approach for the construction of large clusters based on lacunary Dawson-like compounds in the future. Combining the bond valence sums (BVSs) calculated (Table S5) and XPS analysis (Figure a,b and Figure S9), we effectively demonstrate that Ru atoms are in the valence state of +3, and Sb and ordered W atoms display +3 and +6 oxidation states, − respectively.…”

Tetrazine‐Linked Covalent Organic Frameworks With Acid Sensing and Photocatalytic Activity

“…During the reaction of benzylamine and C 6 H 5 ─CH═NH intermediate in the presence of H 2 O 2 , benzaldimine and ammonia are formed. [ 96 ]…”

Photocatalytic Reduction of Nitrobenzene to Aniline by an Intriguing {Ru(C6H6)}-Based Heteropolytungstate

“…Aniline derivatives are generally obtained by the catalytic reduction of nitroaromatic compounds. However, the previous process of nitroarene reduction involved the usage of stoichiometric inorganic reductants and released a lot of waste, which failed to comply with requirements of environmentally friendly development. − At present, photocatalysis technology, which harnesses light as a driving force to conduct a reaction, has become a research hot spot with the advantages of being green and cost-effective − ; a variety of photocatalytic materials have been exploited for the purpose of aniline production, which brought significant advances in the study of nitrobenzene reduction, although with some shortcomings such as the unstable structure, poor selectivity, and poor light responsiveness that prevented them from progressing. ,− Therefore, the development of highly efficient and stable heterogeneous photocatalysts for the selective reduction of nitrobenzene to synthesize aniline in a mild environment is of great importance.…”