伏再辉教授课题组最新研究成果在Applied Catalysis B发表

本网讯 近日，石化新材料与资源精细利用国家地方联合工程实验室伏再辉教授课题组最新研究成果在权威杂志Applied Catalysis B: Environmental（影响因子：7.435）在线发表。全文摘要如下：The formation of photoactive species in the Keggin-type XPMo_12-nV_nO₄₀polyoxometalates (POMs, n = 1-3, X = H⁺, tetramethyl (TMA). tetrabutyl (TBA) or cetyltrimethyl (CTMA) ammonium cation (Q⁺))-HCl system was researched in details by UV–vis and its photo-catalysis performance evaluatedviathe oxidation of cyclohexane by dioxygens (O₂) in acetonitrile (MeCN) under visible light irradiation The results showed that the V^V-O-M (M for V^Vor Mo^IV) sites of POM can capture HCl to form a protonated photoactive species (PA, POM-(V^VOHM)⁺Cl⁻) and the solvent MeCN likely participates the formation of such PA speciesviaweak coordination. This PA species, with a characteristic absorption band of 475 nm, a⁵¹V-NMR chemical shift of −550 ppm and an oxidative potential of higher than 0.9 V, should be responsible for the present photo-catalysis oxidation. The formation of PA species was accelerated significantly with increasing the V atoms incorporated into POMs, but hampered seriously in the presence of slight excess water due to the replaced effect of water for the coordinated HCl and MeCN. Notably, such impediment effect of water was weakened obviously over the Q⁺-containing POMs due to a hydrophobicity of these POM's. As a result, most of the Q⁺-containing POMs showed a higher activity for this photo-catalysis reaction in MeCN-HCl-H₂O media than the H⁺-containing counterparts. Isotope tracing test of water-containing heavy oxygen¹⁸O (97%) in photo-catalysis reaction indicated that the oxygen atoms in water had partly contribution to the formation of cyclohexanol (ca.8.2%) and especially cyclohexanone (ca. 33.3%), which can drastically restrain chlorinated side reactions and thus improve cyclohexanone selectivity. Based on these findings, a free-radical mechanism initiated by the Cl atoms generated in the excited POM-(V^VOHM)⁺Cl⁻species was proposed.