Oxidation Of Alcohols To Esters Using Cobalt-base Material Prepared By Pyrolysis Of ZIF-67

Recently, the use of metal organic frameworks (MOFs) as sacrificial template for thepreparation of nanoporous carbon materials has received considerable attention consideringthe easy decomposition feature of MOFs under high temperatures. Now, MOFs-pyrolyzedmaterials have been applied widely in the fields of electrochemical catalysis, gas adsorption,and separation, etc. However, none of these materials has been reported as catalyst forliquid-phase organic reactions. In this thesis, we developed an novel method for thepreparation of nanoscale metal-based materials from thermolysis of MOFs as highly activecatalysts for liquid-phase catalytic reactions. Because the metal ions in the MOFs areseparated by organic ligands, which will prevent the metal ions from aggregation during theMOF decomposition process, highly dispersed and small metal nanoparticles could beobtained.A zeolite-imidazole type MOF ZIF-67was used as sacrifice template for the directsynthesis of cobalt-based nanomaterials by pyrolysis in Ar. The materials were characterizedby PXRD, elemental analysis, and TEM etc. The characterization data showed that thecobalt-based nanomaterial mainly consisted of cobalt and nitrogen-doped graphite. Cobaltnanoparticles were distributed evenly without serious aggregation.The prepared materials were utilized as catalysts for the oxidative esterification ofalcohols. So far, the reported catalytic systems often involve noble-metal as catalysts andbases as additives, requiring high oxygen pressures or high temperatures. The as-synthesizedcobalt-based nanomaterials by pyrolysis of ZIF–67showed excellent activities andselectivities to the desired esters under base-free and ambient conditions, compatibility with avariety of substrates including the primary aromatic alcohol, aliphatic alcohols, and diols. Thecatalyst prepared by pyrolysis of MOF at800℃exhibited the highest catalytic activity, whichwas mainly due to the suitable carbonization degree, cobalt particle size, and specific surfacearea of the materials. Additionally, the scale-up experiment showed that this catalyst isprospective in the large-scale synthesis. Furthermore, the catalyst was reusable after a simpleH2-reduction treatment. To the best of our knowledge, a catalytic system employingMOF-derived metal nanometerials as catalyst for the liquid-phase transformation has not been reported to date. This methodology provides a new approach for the synthesis of novelcatalysts for liquid-phase catalytic transformations.