The development of visible-light photocatalysts for the selective oxidative coupling of amines to imines is an area of great interest. Herein, four hybrid compounds based on polyoxometalate anions and tris­(bipyridine)ruthenium cations, Ru­(bpy)3[M6O19] (M = Mo, W) 1–2, [Ru­(bpy)3]2[Mo8O26] 3, [Ru­(bpy)3]2[W10O32] 4, are prepared and characterized by X-ray diffraction (single-crystal and powder), elemental analysis, energy-dispersive X-ray spectroscopy (EDS) analysis, infrared (IR) spectroscopy, and solid diffuse reflective spectroscopy. Single-crystal structural analysis indicates that polyoxometalate anions and tris­(bipyridine)­ruthenium cations interact with each other through extensive hydrogen bonds in these compounds. These hybrid species with strong visible-light-harvesting abilities and suitable photocatalytic energy potentials show excellent photocatalytic activity and selectivity for the oxidation of amines to imines at room temperature in air as an oxidant. Among them, compound 1 with the [Mo6O19]2– anion has the highest catalytic activity, which can swiftly convert >99.0% of benzylamine into N-benzylidenebenzylamine with a selectivity of 98.0% in 25 min illumination by a 10 W 445 nm light-emitting diode (LED). Its turnover frequency reaches 392 h–1, which is not only better than the homogeneous catalyst [Ru­(bpy)3]­Cl2 but also much superior to those achieved over most of reported heterogeneous catalysts. Moreover, it shows a wide generality for various aromatic amines, accompanied by the advantages of good recyclability and stability. The photocatalytic oxidation mechanism of amines to the corresponding imines over polyoxometalate-based hybrid compounds was fully investigated.

The selective oxidation of organic sulfides is a pivotal avenue to prepare sulfoxides that can act as synthetic intermediates of fine chemicals, bioactive molecules, and asymmetric catalysis ligands. To construct...

Selective oxidation of alkyl-substituted phenols offers an ideal pathway to synthesize p-benzoquinones (p-BQs), but it is known to be inefficient because of the parallel competing reactions. Aiming at the design and synthesis of more powerful heterogeneous catalysts for highly efficient synthesizing functionalized p-BQs, herein, we report two crystalline catalysts with supramolecular networks based on Dawson-type polyoxometalates 2), where ptz = 5-(4-pyridyl)-1H-tetrazole and ina = isonicotinic acid. Structural analysis shows that 1 is formed by the supramolecular contact between one-dimensional POM inorganic chains and two kinds of trinuclear Cu-organic clusters, while 2 is formed by supramolecular stacking of ladder-like one-dimensional chains that are composed of ribbonlike nonanuclear Cu-organic clusters and POM anions. Both supramolecular catalysts exhibit high catalytic activity in H 2 O 2 -based oxidation of phenols/aromatics to p-BQs. Strikingly, in the synthesis of trimethyl-p-benzoquinone (TMBQ, an intermediate of vitamin E) by oxidizing 2,3,6trimethylphenol, the conversion, selectivity, and oxidant efficiency can reach >99, 97.9, and 85.0% for 1, as well as 95.4, >99, and 79.8% for 2 within 5 min, respectively. Also, the catalytic activities of 1 and 2 presented by the turnover frequency are 12 000 (the highest thus far) and 7632 h −1 , respectively. Detailed structure−activity analysis revealed that the higher performance of 1 is attributed to the more active-site accessibility due to the supramolecular interactions between POM and Cu organic units in the framework. Moreover, the observed yield of TMBQ has not decreased and the skeleton of catalysts has not changed in >10 cycles. The reaction mechanism was also systematically studied, and the parallel dual center, namely, Cu-site and POM, -driven reaction processes (radical and oxygen transfer) were illuminated.