title: Hybrid polyoxotungstate/MIL-101 materials: synthesis, characterization, and catalysis of H2O2-based alkene epoxidation.
abstract: Polyoxotungstates [PW(4)O(24)](3-) (PW(4)) and [PW(12)O(40)](3-) (PW(12)) have been inserted into nanocages of the metal organic framework MIL-101. The hybrid materials PW(x)/MIL-101 (x = 4 or 12) containing 5-14 wt % of polyoxotungstate have been obtained and characterized by elemental analysis, N(2) adsorption, FT-IR, Raman, and (31)P NMR MAS spectroscopic techniques. Their catalytic performance was assessed in the selective oxidation of alkenes with aqueous hydrogen peroxide under mild reaction conditions ([H(2)O(2)] = 0.1-0.2 M, 50 degrees C, MeCN). PW(x)/MIL-101 enclosing 5 wt % of polyoxotungstate demonstrated fairly good catalytic activities in the epoxidation of various alkenes (3-carene, limonene, alpha-pinene, cyclohexene, cyclooctene, 1-octene), the turnover frequencies (TOF) and alkene conversions were close to the corresponding parameters achieved with homogeneous PW(x). For the oxidation of substrates with aromatic groups (styrene, cis- and trans-stilbenes), a higher level of olefin conversion was attained using PW(12)/MIL-101. Moreover, confinement of PW(12) within MIL-101 nanocages allowed us to reach higher epoxide selectivities at higher alkene conversions. The hybrid PW(x)/MIL-101 materials were stable to leaching, behaved as true heterogeneous catalysts, were easily recovered by filtration, and reused several times with the maintenance of the catalytic performance.
authors.affiliation: Boreskov Institute of Catalysis, Lavrentiev Avenue 5, Novosibirsk, 630090, Russia.
authors.forename: Nataliya V
authors.initials: NV
authors.lastname: Maksimchuk
authors.forename: Konstantin A
authors.initials: KA
authors.lastname: Kovalenko
authors.forename: Sergey S
authors.initials: SS
authors.lastname: Arzumanov
authors.forename: Yurii A
authors.initials: YA
authors.lastname: Chesalov
authors.forename: Maxim S
authors.initials: MS
authors.lastname: Melgunov
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Stepanov
authors.forename: Vladimir P
authors.initials: VP
authors.lastname: Fedin
authors.forename: Oxana A
authors.initials: OA
authors.lastname: Kholdeeva