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Highly Selective H 2 O 2 ‐Based Oxidation of Alkylphenols to p ‐Benzoquinones Over MIL‐125 Metal–Organic Frameworks
Author(s) -
Ivanchikova Irina D.,
Lee Ji Sun,
Maksimchuk Nataliya V.,
Shmakov Alexander N.,
Chesalov Yurii A.,
Ayupov Artem B.,
Hwang Young Kyu,
Jun ChulHo,
Chang JongSan,
Kholdeeva Oxana A.
Publication year - 2014
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201301098
Subject(s) - chemistry , catalysis , metal organic framework , adsorption , inorganic chemistry , leaching (pedology) , alkyl , metal , selectivity , titanium , raman spectroscopy , heterogeneous catalysis , crystallite , fourier transform infrared spectroscopy , amine gas treating , nuclear chemistry , organic chemistry , chemical engineering , physics , environmental science , soil science , optics , soil water , crystallography , engineering
The titanium‐based metal–organic framework MIL‐125 and its amine‐functionalized analog, MIL‐125_NH 2 , have been synthesized and characterized by elemental analysis, XRD, SEM, TEM, N 2 adsorption measurements, and spectroscopic techniques, including FTIR, Raman, and DR UV/Vis spectroscopy. Catalytic properties of MIL‐125 and MIL‐125_NH 2 were evaluated in the selective oxidation of two representative alkyl‐substituted phenols, 2,3,6‐trimethylphenol and 2,6‐di‐ tert ‐butylphenol, with the clean oxidant H 2 O 2 . With both MIL‐125 and MIL‐125_NH 2 , the selectivity toward the corresponding p ‐benzoquinones was 100 %. Samples of MIL‐125 with different sizes of crystallites (0.5, 1.5, and 5 μm) demonstrated similar reaction rates, thus indicating the absence of diffusion limitations. The efficiency of the oxidant utilization and stability of the MIL‐125 structure increased upon decreasing the amount of water in the reaction mixture. Even if the structural integrity of MIL‐125 was destroyed by the reaction medium, the metal–organic framework acted as a precursor for the highly active, selective, and recyclable catalyst. The MIL‐125‐derived materials were stable toward titanium leaching, behaved as true heterogeneous catalysts, and could easily be recovered by filtration and reused several times without the loss of the catalytic properties.