Preparation Of Magnetic Biochar-supported Catalysts And Study On Catalytic Synthesis Of Spiro Compounds

In recent years,due to the requirements of low-carbon economy and sustainable development,the preparation of functional biomass-based carbon materials using cheap,accessible and renewable biomass as the raw material has attracted extensive attention.Biochar is mainly a kind of carbon material with rich pore structure and high carbon content prepared by high temperature pyrolysis of agricultural and forestry waste biomass under anaerobic or anoxic conditions.The overall structure is highly aromatic and has high stability,which is not easy to be oxidized.And that source of raw material is very wide,such as wood,reed,fruit shell,livestock manure,garbage,sludge and the like.The surface has high density of carbonyl,carboxyl and hydroxyl functional groups,which makes its surface modification can produce new economic catalyst.Biochar is a multifunctional carbon material.It has been widely reported in the fields of soil modification,adsorption,agricultural waste recovery,climate change mitigation,water resource protection and energy production.However,the research in organic synthesis has just started,with only a few reports.Therefore,using corncob as biomass to prepare biochar and loading magnetic materials(CoFe₂O₄),three magnetic catalysts were prepared,namely CoFe₂O₄/BC-SO₃H,CoFe₂O₄/BC/PDA-Ni,CoFe₂O₄/BC-ZrO_2.These materials have been characterized by infrared spectroscopy(FT-IR),X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),energy dispersive analysis(EDS),thermogravimetric analysis(TGA),pore and surface analysis(BET)and vibrating sample magnetometer(VSM)techniques were used for analyzing the prepared catalyst.The prepared catalysts exhibited excellent catalytic activity for synthesis of three types of spiro compounds.In the second chapter,CoFe₂O₄/BC-SO₃H was prepared and applied as heterogeneous catalyst for the synthesis of biologically important spiro-pyrazolo[3,4-b]pyridine derivatives via one-pot three-component reaction with readily available 1H-pyrazol-5-amine,isatin and 3-oxo-3-phenylpropanenitrile as the starting materials.In addition,the catalyst can be recovered easily from the reaction mixture by simple magnetic attraction and reused for five consecutive cycles without any significant loss in activity.In the three chapter,a facile and versatile strategy has been developed for preparation of a novel magnetic biochar catalyst with NiNPs sandwiched between the PDA modified CoFe₂O₄core–shell structure(CoFe₂O₄/BC/PDA-Ni).The prepared catalyst exhibited excellent catalytic activity for synthesis of spirooxindole-dihydropyridines derivatives by a one-pot three-component reaction of isatin,barbituric acid and 6-amino uracil or 1H-pyrazol-5-amine.Furthermore,the catalyst could be conveniently separated from the reaction solution by using an external magnet and recycled at least six times without notable reduction in its activity.In the four chapter,a novel magnetic biochar supported catalyst was prepared via a simple synthetic route(CoFe₂O₄/BC-ZrO₂).The prepared catalyst exhibited excellent catalytic activity for synthesis of Spirobenzodiazepine derivatives via one-pot three-component reaction of phenylenediamines,isatin and furandiones.The catalyst could be readily recovered and reused several times without an obvious decay of catalytic performance.A total of 97 compounds were synthesized,all of which were analyzed and identified by IR,¹H NMR,¹³C NMR and mass spectrometry.