An Important Photocatalysis Oxidation: Selective Oxidation of Aniline to Azobenzene over a {P₄Mo₆}-based Crystalline Catalyst Under Visible-light Irradiation at Room Temperature

Abstract

Selective oxidation of aniline to azobenzene with a higher economic value is significant for modern industrial production. However, the high reaction temperature and undefined catalytic reaction center always limit the promotion of this reaction. Here, we designed and synthesized a new [P4MoV 6O31]12–-based cobalt-containing complex (Hbiz)5{Co(H2O)3[Co(H2O)2]2}{Co[Mo6O12(OH)3(PO4)(HPO4)3][Mo6O12(OH)3(PO4)2(HPO4)2]}·3H2O (1; biz = benzimidazole) under solvothermal conditions. Using 1 as the photocatalyst, the visible-light-driven conversion of aniline to azobenzene at room temperature was realized for the first time (conversion rate 97%, selectivity 96% of azobenzene, reaction time of 12 h). Additionally, real sunlight irradiation can produce a comparable outcome in 48 h. The mechanism investigation manifested that the Mo and Co centers in 1 acted as Brönsted and Lewis acid centers, synergistically promoting the aniline oxidation reaction. This research advances the application of polyoxometalate-based photocatalysts while also offering a sustainable and effective method for producing azobenzene.

N–N-Bridged Polynuclear POM-Based Coordination Polymers Based on a V-Type Ligand: Proton Conduction and Magnetism

“…The Cu–O and Cu–N bond lengths are 1.919(8)–2.397(14) and 1.972(11)–2.010(11) Å, respectively. All molybdenum ions are in a +6 oxidation state, as confirmed by the XPS data of Mo 3d with peaks at 232.4 and 235.5 eV …”

Assembly of Lanthanide-Containing 3D [MnMo9O32]6–-Based Metal–Organic Frameworks and Oxidative Desulfurization Performance

“…All three Pr­(III) ions exhibit tricapped trigonal prism configurations based on the continuous shape measurements (CShM) conducted via the Shape software (Figure S4), with details compiled in Table S5. , In the [MnMo 9 O 32 ] 6– anion, both the central Mn and nine Mo ions exhibit O 6 octahedral coordination environments, and the oxidation states of Mn and Mo are identified as +4 and +6, respectively, according to bond valence sum (BVS) calculations (Table S6). The binding energies of 232.6 and 235.7 eV in the X-ray photoelectron spectroscopy (XPS) of compound 2 correspond to 3d 5/2 and 3d 3/2 of Mo VI , while those of 642.5 and 645.3 eV can be assigned to the 2p 3/2 and 2p 1/2 of Mn IV (Figure S5), − which provide further proof of the valences of Mn and Mo. The Mn–O and Mo–O bond lengths are in the ranges of 1.883–1.903 and 1.685–2.295 Å, respectively, while the Pr–O/N bond lengths range from 2.443 to 2.847 Å, which are consistent with those reported of similar compounds. ,− The Mn–O–Mo bond angles are between 99.6 and 102.5°.…”

A new {P4Mo6}-based complex as a highly efficient heterogeneous catalyst for the oxidation of alkylbenzenes under mild conditions

“…According to previous research results, the oxidation process of diphenylmethane mainly involves the formation of peroxyl radicals and carbon radicals. 26,40 To clarify the mechanism of the catalytic reaction, butyl hydroxytoluene (BHT) was introduced into the reaction system as an oxygen radical scavenger, and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) as a carbon radical scavenger. The experimental results showed that the introduction of BHT and TEMPO resulted in a significant decrease in the conversion of the reaction (Fig.…”

“…For example, our group used the Co-based {P 4 Mo 6 } complex obtained under solvent conditions to realize the photocatalytic oxidation process of aniline to azobenzene at room temperature. 40 Han's group used a {P 4 Mo 6 }-based catalyst constructed with Al( i ) to synthesize 1,5-benzodiazepine drugs under solvent-free conditions. 41 However, the application of {P 4 Mo 6 }-based CPs in the field of catalytic oxidation of saturated C–H bonds has not been explored.…”