Preparation Of Functionalized Metal Organic Frameworks And Their Applications In Catalytic Biomass Conversion

Fossil resources will run out eventually,renewable resources to replace which to produce liquid fuels and chemical raw materials of organic chemicals are urgent demanded.Biomass is considered as a source of widespread,most abundant,low pollution,and the only renewable organic carbon resource,which has drawn much attention for being a substitute for chemical raw materials.In this thesis,we design and prepare four series and ca.20 catalysts of unfunctional and functional metal-organic frameworks materials for efficient synthesis of organic molecules with wide application including lactic acid?La A?,5-ethoxymethylfurfural?EMF?,ethyl levulinate?EL?,5-hydroxymethylfurfural?HMF?,and so on from biomass-derived carbohydrates.Aiming at the existence problems of solid acidic catalysts,we have designed the specific and targeted catalyst,investigated the preparation methods,characterization of catalysts structures,as well as the catalyst reusability.Two different classes of catalysts or catalytic systems with excellent structure propertied and stable and efficient catalytic performance have been screened and developed to be capable of producing above-mentioned molecules in high selectivity.Innovative results and main conclusions are discussed and listed as follows:1.Unfunctional metal-organic frameworks materials for production of La A from monosaccharideMIL-101?Fe?was optimized and screened for the catalytic transformation of glucose and fructose into La A.The as-synthesized MIL-101?Fe?with moderate acidic density and strength was demonstrated to contribute greatly to the pronounced catalytic performance in glucose-to-La A conversion?25.4% yield?,as compared with other catalysts like MIL-101?Al,Cr?and series Ui O-66?Zr?.The effects of reaction conditions including temperature,reaction time,and substrate were explored.2.Efficient catalytic conversion of carbohydrates into EMF over one-pot MIL-101?Cr?-SO₃H?x?A series of MIL-101-SO₃H?x?polymeric materials were prepared and further used for the first time as efficient heterogeneous catalysts for the conversion of fructose-based carbohydrates into EMF in a renewable mixed solvent system consisting of ethanol and THF.The influence of-SO₃ H content on the acidity as well as on the catalytic activity of the porous coordination polymers in EMF production was also studied.High EMF yields of 67.7% and 54.2% could be successively obtained from fructose and inulin in the presence of MIL-101-SO₃H?100?at 130 °C for 15 h.The catalyst could be reused for five times without significant loss of its activity and the recovery process was facile and simple.This work provides a new platform by application of porous coordination polymers?PCPs?for the production of the potential liquid fuel molecule EMF from biomass in a sustainable solvent system.3.Efficient conversion of furfural alcohol?FA?to EL with one-pot MIL-101?Cr?-SO₃HCatalytic ethanolysis of FA to EL with MIL-101?Cr?-SO₃ H,prepared by simple one-pot hydrothermal treatment,is presented for the first time.The as-prepared catalyst with high surface area,hydrothermal and chemical stability,good dispersion,and feasible accessibility of-SO₃ H Br?nsted acid sites was found to show superior performance to other sulfonic acidfunctionalizedsolid catalysts.Besides the special textural properties,the obtained good catalytic activity of 79.2% EL yield and 100% FA conversion were also dependent on the density and strength of the Br?nsted acid and the reaction parameters.A slight loss of catalytic activity after five consecutive recycles and the hot filtration experiment confirmed the good stability of MIL-101?Cr?-SO₃ H.Two coexisting reaction paths for the ethanolysis of FA to EL catalyzed by MIL-101?Cr?-SO₃ H were proposed,wherein 2-ethoxymethylfuran?2-EMF?was observed to be the dominant intermediate.4.Efficient conversion of glucose to HMF using meso-MIL-101?Cr?-SO₃H?MMS?synthesized by PSM sulphonationMMS was synthesized by using hydrothermal method and chlorosulfonation.The resulting mesoporous material with high SBET,large pore size and pore volume was efficient for producing HMF from glucose,and an optimized HMF yield of 51.4% at a glucose conversion of 95% was obtained within 10 h at 140 °C.The effects of reaction temperature,time,catalyst amount,solvents and substrate type on conversion of glucose to HMF were also investigated.The excellent structure properties were found to play a key role in glucose-to-HMF conversion.5.Mesoporous acidic MIL-101?Cr??MMS?synthesized by PSM sulphonation for efficient conversion of FA to ELEnlarging the microporous of MOFs to the meso-structure improved the accessibility of acidic sites for substrates.With the regulable of CTAB/Cr³⁺ and Cl SO₃ H sulphonation,different mesopore size and acidic properties of MMSs were synthesized and applied to the ethanolysis of FA to EL for the first time.The optimal catalytic activity of 83.8% EL yield and full FA conversion demonstrated the appropriate mesopore size and accessible acidic density contributed to the superior performance of the MMS?0.3?-0.15.The high turnover frequency?TOF?value?14.8 h-1?was comparable to the commercial Nafion NR50?18.3 h-1?and far beyond the classical Amberlyst-15?1.9 h-1?confirming the superior integrated performance.Furthermore,the two co-existence reaction paths with 2-EMF and 4,5,5-triethoxy-2-pentanone-1-one?TEP?as intermediates are most the possibility.6.Heteropolyacid encapsulated in metal-organic framework as catalysts for fructose dehydration to HMFMOFs,is known for its very large pore size,large surface area and good stability and heteropolyacid is soluble in organic solvent with strong acidity.However,in view of the applications of MOFs in catalysis for the microporous are still limited and the drawback of heteropolyacid,the combination of the POM and MOFs is imperative.HMF has been considered a renewable chemical platform for the production of liquid fuels and fine chemicals.Heteropolyacid,encapsulated in MOFs is evaluated as a potential catalyst for the selective dehydration of fructose and glucose to HMF.The results demonstrate that PMA/Ui O-66?Zr?is effective for HMF production from fructose in DMSO.This is the first example of the application of a metal-organic framework in carbohydrate dehydration.