Engineering active sites in MOF, MOF-derived, and carbonbased materials for sustainable catalysis

Abstract

The performance of functional materials towards a wide variety of applications can be significantly improved by introducing an optimum porosity. Thus, developing a new class of porous materials is advantageous as a heterogeneous catalyst in various sustainable catalytic processes. Several outstanding and benchmark porous catalysts, such as zeolite, metal-oxide, activated carbon, metal-organic framework (MOF), coordination polymers, etc., have garnered the greatest research attention due to their special and unique properties of the porous framework. In this thesis, MOF and carbon-based materials were particularly focused on due to their high functional nature and their unique structural properties of carrying the homogeneously distributed metallic sites as active centers. Furthermore, their structural modifications also provide numerous opportunities to develop new classes of highly catalytically active heterogeneous catalysts. MOF is a class of porous coordination polymer comprised of a highly crystalline framework structure with a large surface area, exhibiting the properties of both inorganic and organic components within a single framework. The functional and tunability nature of MOF structure allows further modifications through its active site engineering by direct-synthesis modification (de Novo) and post-synthetic modification (PSM) of UIO-66 MOF. The metal node engineering by the Nb incorporation of UIO-66 catalyst was developed to improve the glucose to fructose isomerization reaction. Moreover, the UIO-66 modification in terms of the organic linker missing was employed in the noble metal-free catalytic transfer hydrodeoxygenation (CHDO) of vanillin. The desired catalytic activities were introduced by decoration metal NPs by PSM strategy. Cu and Pd NPs embedded Cu-BTC, Ce-BTC, and NH2- MIL-125(Ti) were synthesized and employed in reducing various unsaturated organic functional groups, hydrogenolysis of the lignin model compounds under mild reaction conditions, and formic acid mediated reductive formylation of nitrobenzene derivative in LEDs. The thermal instability of MOF frameworks has provided an opportunity to prepare metals/metal oxides embedded carbon materials. Several MOF-derived materials were prepared to obtain modulated and fascinated catalyst surfaces and the highly accessible metallic sites that served as the homogeneously dispersed active centres in the background of MOFderived graphitic carbon. Their catalytic applications were extended in the reductive formylation of nitrobenzene, Pd-free Sonogashira coupling reaction, and hydrodeoxygenation of vanillin and it’s homologous under mild reaction conditions. The reduction and reductive formylation of N-heterocyclic compounds such as quinoline and its homologous compounds was carried out using N-modified ordered mesoporous carbon-based Co embedded catalysts obtained by hard template mediated synthesis strategy. Furthermore, the reduction and reductive amination of LA, a lignocellulosic model compound, were carried out using formic acid over CoPd embedded-N-doped ordered porous carbon. Overall, the thesis provides strategies for developing simple, robust, and cost-effective MOFs and carbon-based catalytic materials for the sustainable production of biomass-derived chemicals/fuels and other important synthetic intermediates.