Metal-Organic Frameworks-based Composites For Catalytic Transformation Of Biomass-derived Furanic Platform Molecules

The conversion of renewable biomass resources into fuels,polymers,and fine chemicals provides potential solutions to the shortage of fossil resources,environmental pollution and a possible crisis in energy supply.Furfural and 5-hydroxymethylfurfural?HMF?,typical represents of furanic biomass-derived platform molecules,are regarded as the bridges between raw biomass and high-valued chemicals.However,current catalytic systems often suffer from unsatisfied activities,selectivities and sabilities,and are mostly toxic,corrosive and costly,far from meeting the industrial regulations for scale-up production.Metal-organic frameworks?MOFs?are a new class of porous zeolite-liked materials formed by the self-assembly of inorganic metal cations and nitrogen-containing organic ligands.Compared with the traditional porous materials,MOFs have unique properties like tunable functional structures,high specific surface areas and pore volumns,which have shown great potential in heterogeneous catalysis.Based on the above backgrounds,aiming at providing solutions to the key problems encountered in tranformations of biomass-derived platform molecules?e.g.,furfural and HMF?,we have developed novel strategies for the synthesis of MOFs-based composites with unique structures by employing MOFs as supports or sacrificing templates.Moreover,the structure-performance relationships and plausible reaction mechanism have been investigated.The main contents of this thesis are as follows:Ru nanoparticles were uniformly distributed on the surface of the acidic MIL-101 to synthesize a series of Ru/MIL-101 catalysts.The 3 wt%Ru/MIL-101 catalyst exhibited outstanding catalytic performance in converting furfural to cyclopentanone under mild conditions?160oC,4 MPa H₂?and achieved a>96%yield of cyclopentanone.The catalyst could be reused six times without any substantial change in activity and selectivity.The excellent catalytic performance of the Ru/MIL-101 catalyst could be attributed to the homogeneously dispersed Ru namoparticles?4-5 nm?and the special structural and acid properties of MIL-101.A Fe-Co bimetallic catalyst was derived from MIL-45b that was employed as the sacrificing template.The Fe-Co bimetals existed as Fe₃Co₇ in the resulted catalyst.The as-synthesized catalyst had novel hollow sphere nanostructures and exhibited high efficiencies in oxidation conversion of HMF into DFF under mild conditions?100oC,1 MPa O₂?with a high DFF yield?>99%?,which could be comparable to that obtained with noble metal catalysts.The magnetic catalyst could be easily separated after reaction and reused up to six runs without any significant loss in reactivity.Studies indicated that the hollow structures favored the adsorption of HMF and quick desorption of the formed DFF from the catalyst surface and led to the highly efficient transformation of HMF into DFF.A sulfur doped Fe/C-S catalyst was prepared by a pyrolysis method using MIL-88B as a template and sulfur powder as a dopant.The as-synthesized catalyst possessed small quantities of acidic sulfur-derived functional groups with highly uniform octahedral nanoparticles featuring Fe₃O₄?111?exposed facets.The catalyst had high dehydration and oxidation activity and achieved quantitative yields for DFF from fructose.Studies indicated that the superior selectivity to DFF was related to the low adsorption energy of DFF on Fe₃O₄?111?facets as well as the existence of non-oxidative sulfur-derived functional groups that made the catalytic system less oxidative.A novel MOFs-templated strategy was developed for the encapsulation of ultrafine metal-oxides nanoparticles within mesorpores.Co,Fe,Cu,and Ni oxides nanoparticles were confined within the mesopores of KIT-6 and uniformly distributed with high metal loadings?up to 13.6 wt%?.The synthesis was facile,which only involved self-assembly of MOF precursors in the mesopores of KIT-6 and a subsequent calcination process to convert the MOF into metal-oxide nanoparticles.The as-synthesized Co@KIT-6 material exhibited superior catalytic activity in HMF transformation,achieving a complete HMF conversion and a>99%2,5-furandicarboxylic acid selectivity with TOF values as high as 150 h^-1,which was ca.3-150 times greater than those of the previously reported catalysts.Besides,the Co@KIT-6 catalyst could be reused up to six runs without any significant loss in reactivity.Studies indicated that the significantly improved activity and stability of the catalyst was attributed to the nano-confinement effects of the mesopores,which prevent ultrafine oxide nanoparticles from aggregating and leaching during the reaction.