Synthesis and alcohol catalytic properties of TEMPO functionalized Zr-based MOFs
ZHUANG Jin-liang1, LIU Xiang-yue1,2, DU Xuan3
1. Key Laboratory of Functional Materials and Chemistry of Guizhou Province, School of Chemistry and Materials, Guizhou Normal University, Guiyang 550001, China;
2. College of Chemistry, Fuzhou University, Fuzhou 350108, China;
3. Key Laboratory of Green Process and Engineering, CAS, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
Abstract：A strategy based on grafting organocatalytic units as side-chain on the organic linkers, a TEMPO radical decorated terphenyl-dicarboxylic acid linker was synthesized. By employing acetic acid as modulator, TEMPO radical decorated UiO-68-TEMPO nanocrystals were synthesized by using H2tpdc-TEMPO as organic linker and ZrOCl2 as metal source under solvothermal conditions. UiO-68-TEMPO are monodispersed nanocrystals with side in the range of 800-1200 nm, with high BET areas (up to 1320 m2/g), and contain a large number of TEMPO radicals as evidenced by solid-state EPR spectrum. UiO-68-TEMPO nanocrystals enable selective oxidation of a broad range of alcohols, including primary aromatic alcohols, secondary aromatic alcohols, and heterogeneous atomic alcohols, with high efficiency and selectivity. The catalytic activity of UiO-68-TEMPO nanocrystals remains 75% after catalysis for four cycles. Finally, a plausible catalytic mechanism for the oxidation of benzyl alcohol by UiO-68-TEMPO was proposed, that is the TBN co-catalyst produces NO2/NO redox mediator, which enables the oxidation of TEMPO radicals to oxoammonium cations by O2, and finally oxidize benzyl alcohol to benzaldehyde.
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