Multiunit Catalysts with Synergistic Reactivity: Three-Dimensional Polyoxometalate-Based Coordination Polymers for Highly Efficient Synthesis of Functionalized -Benzoquinones.

The rational design of highly efficient catalysts for the synthesis of functionalized -benzoquinones (-BQs) is of great significance for the manufacture of bioactive compounds. Herein, two 3D crystalline polyoxometalate-based coordination polymers (POMCPs) are used as heterogeneous catalysts for the synthesis of -BQs, which are H[Cu(ttb)(HO)][Cu(ttb)Cl][PWO]·4HO () (Httb = 1-(tetrazol-5-yl)-4-(triazol-1-yl)benzene) and [ClCu(trz][ClCu(trz)][Cu(HO)][PWO] () (trz = 1,2,4-triazole). Both compounds were characterized by elemental analysis, IR, XPS, solid diffuse reflective spectroscopy, TG analysis, and single-crystal X-ray diffraction. In , Keggin anions [PWO] locate in 1D square channels constructed from wave-like Cu-ttb layers to form a 3D POMCP by coordinating to Cu ions, and in , [PWO] anions situate in eight-membered Cu-trz channels via Cu···O interactions to yield a 3D POMCP structure. The catalytic activities of and have been evaluated in the selective oxidation of alkylphenols/alkoxybenzenes/methylnaphthalene, especially in the oxidation reaction of 2,3,6-trimethylphenol (TMP) to 2,3,5-trimethyl--benzoquinone (TMBQ, vitamin E key intermediate), with HO as oxidant. By using catalysts and under optimal conditions, the yield of TMBQ can reach 99% and 96% within 10-20 min, respectively. Both catalysts demonstrated high turnover frequencies (300 h for and 600 h for ) and the truly heterogeneous nature. and catalyzed the synthesis of -BQs on the basis of effective cooperative catalytic activities by POMs and metal nodes.