Construction Of The Active Sites Based On Metal-organic Frameworks (MOFs)for Catalyzing The Transformation Of Biomass-derived Furfural

Furfural?FUR?,a significant bio-based platform chemical,is regarded as one of versatile and important building blocks for generating a series of value-added products by selective oxidation,oxidative esterification,catalytic hydrogenation,aldol condensation and oxidative condensation.The key to realize the efficient valorization of furfural is to design and develop the highly active catalyst.Metal-organic frameworks?MOFs?is a kind of porous material with periodic multi-dimensional network structure.In recent years,it has attracted wide attentions in the field of heterogeneous catalysis.The purpose of this paper is to build the catalytic active sites from the MOFs,so as to attain new heterogeneous catalyst system,and further promote the conversion of biomass platform chemical furfural so that a low-cost,rapid and environment-friendly way for the efficient valorization of furfural is developed.The specific research content can be divided into the following three parts:?1?A series of heterogeneous catalysts?Au@UIO-66-X?were prepared by loading gold nanoparticles onto UIO-66 and functionalized UIO-66-X?X=-NH₂,-SO₃H,-COOH,-NO₂?,and applied to the oxidation process of furfural and aliphatic alcohols.It is found that Au@UIO-66 catalyst can efficiently catalyze the oxidative esterification of furfural with methanol,of which the conversion of furfural can reach99.9%,and the selectivity of methyl-2-furoate can reach 99.9%.In the process of oxidation of furfural and ethanol,based on UIO-66 vector functional treatment,can achieve the effective regulation of oxidative esterification and condensation of two competition process,Au@UIO-66-SO₃H catalyst can make the furfural conversion rate reached 74%,the selective oxidation of the condensation products of up to 96%.The Au@UIO-66 catalyst could lead to the oxidation and esterification of the reaction,the conversion of furfural reached 44%and the selectivity of ethyl furfurate was 40.2%.In addition,we optimized the preparation method of the catalyst,using X-ray ray diffraction?XRD?,High resolution scanning electron microscopy?HRSEM?,high resolution transmission electron microscopy?HRTEM?,X-ray ray photoelectron spectroscopy?XPS?,Fourier transform infrared spectroscopy?FT-IR?,Inductively coupled plasma emission spectrometer?ICP-OES?and the structure of the new system the preparation and circulation after using Au@UIO-66-X catalysts.The related structural characterization and cyclic catalytic performance test showed that Au@UIO-66-X had good stability under the established reaction conditions.?2?The MOF-5 supported platinum nanoparticles catalyst?Pt@MOF-5?was prepared by the impregnation hydrogen reduction method and applied to the catalytic oxidation of furfural and ethanol.It is found that under optimal conditions,the conversion of furfural can reach84.1%,and the selectivity of target product 3-?2-furan?acrolein can reach 90.1%.After five cycles,the activity of catalyst remains basically unchanged.In addition,we use X-ray ray diffraction?XRD?,High resolution scanning electron microscopy?HRSEM?,High resolution transmission electron microscopy?HRTEM?,X-ray ray photoelectron spectroscopy?XPS?,Fourier transform infrared spectroscopy?FT-IR?,Inductively coupled plasma emission spectrometer?ICP-OES?and other structures of the new preparation and after recycling Pt@MOF-5 catalysts,the results show that Pt@MOF-5 with high activity and stability can be attributed to the platinum nanoparticles?2 nm?uniform embedded in the pores of MOF-5.?3?2D Co-MOFs and 2D Ni-MOFs were synthesized.Heat treated 2D Co-MOFs obtained two highly active catalytic species?ACS-I and ACS-II?,which can efficiently catalyze the oxidative condensation of furfural with aliphatic alcohols.The heat treatment temperature of catalyst ACS-I corresponding to 300 ^oC,it can make the furfural conversion was 63.4%,the selectivity of 2-methyl-3-?2-furyl?acrolein was 99.5%;the heat treatment temperature of catalyst ACS-II corresponding to 700 ^oC,it can make the furfural conversion was 84.9%,the selectivity of 2-methyl-3-?2-furyl?acrolein was 99.7%;X-ray ray diffraction?XRD?,High resolution scanning electron microscopy?HRSEM?,High resolution transmission electron microscopy?HRTEM?,X-ray ray photoelectron spectroscopy?XPS?and Fourier transform infrared spectroscopy?FT-IR?,Inductively coupled plasma emission spectrometer?ICP-OES?.The characterization results show that the catalytic active species of ACS-I is achieved by removing the Co Center axial coordination water the molecule,ACS-I in 2D layer to keep the MOFs and make the central metal Co exposed the catalytic active sites;ACS-II is a carbon based nano Co_xO_y-N composite material removal organic framework derived.