Abstract
The aim of the project is the synthesis of lanthanum metal organic frameworks with azole based linkers as catalysts for the oxidation of olefins to aldehydes and epoxides. The organic struts of azole based linkers 4-((1-(4-carboxyphenyl)-1H-1,2,3-triazol-4-yl)methoxy)-3- methoxybenzoic acid (18), 5-((1-(4-carboxyphenyl)-1H-1,2,3-triazol-4- yl)methoxy)isophthalic acid (23), 5-(4-((3,5-dicarboxyphenyl)methyl)-1H-1,2,3-1-yl) isophthalic acid (26) and 4,4ˈ-(2H-tetrazole-2,5-diyl)dibenzoic acid (28) were successfully synthesized using copper-catalyzed click chemistry reaction of azides and alkynes. Their structures were confirmed using nuclear magnetic resonance spectroscopy (NMR), high resolution electrospray ionization mass spectrometry (ESI-MS), and elemental analysis. The metal organic frameworks were synthesized by mixing lanthanum nitrate hexahydrate and the azole based linker organic struts in dimethylformamide solvent using solvothermal technique. Other synthesis methods such as solvent evaporation and diffusion techniques were also attempted for the synthesis of crystalline metal organic frameworks. The slow evaporation method of synthesis provided UJMOF-1 (La-triazole 18 MOF) as a crystalline product suitable for single X-ray diffraction analysis. All the attempted synthesis methods for UJMOF-2, UJMOF-3 and UJMOF-4 did not provide crystalline product suitable for single crystal X-ray diffraction analysis. However, the solvothermal synthesis for all the MOFs provided microcrystalline powder solid products. The products were characterized using different characterization techniques such as acid digestion 1H NMR, EA, IR, ESI-MS, SEM-EDX, PXRD, ICP-OES, BET, TGA and DSC methods, which provided substantial support for the formation of the proposed lanthanum based metal organic frameworks. The MOFs showed good catalytic activities for the oxidation of olefins to aldehydes and epoxides, using hydrogen peroxide and tert-butyl hydroperoxide, respectively, as oxidizing agents in the presence and absence of additives after heating at 70-80 °C in acetonitrile solvent for 24 hours.
Ph.D. (Chemistry)