Synthesis And Application Of Magnetic Metal-Organic Framework Catalysts In Organic Synthesis

Metal–organic frameworks?MOF_s?,a kind of compound with three-dimensional porous structure,constructed from metal ions or metallic clusters and multidirectional organic linkers have attracted considerable attention as an emerging class of potentially useful porous crystalline materials for several reasons: their large specific surface areas;tunable pore distributions;more active;outstanding thermal mechanical;high acid–base catalytic activities;and ease of functionalization and design.By virtue of these special properties,MOF_s have unquestionable potential for practical applications in a wide range of fields,such as gas adsorption/storage,separations,chemical sensors,thin-film devices,photoluminescence,drug carriers,or biomedical imaging.Recently,the use of MOF_s as heterogeneous catalysts in organic synthesis has a wide range of applications at present.However,it is difficult to ensure complete separation and recycling of MOF-based heterogeneous catalysts from the reaction solutions.Therefore,if MOF_s are combined with magnetic components,the resulting magnetic MOF_s will show magnetic susceptibility.So the research of magnetic MOF_s becomes more necessary.We prepared a series of highly active and easily recyclable MOF-based porous magnetic core–shell materials?CoFe₂O₄@SiO₂@IRMOF-3,Co Fe2O4@SiO2@MOF-5,CoFe₂O₄@SiO₂@Cu-BTC?.The structure and property of the prepared catalysts was characterized by SEM,TEM,XRD,FT-IR,N₂ adsorption-desorption,TG and VSM.Finally,we used them as efficient catalysts for the synthesis of functionalized dihydro-2-oxopyrroles,3,4,5-substituted furan-2?5H?-ones,1,3-oxazines respectively.The foremost achievements are as followings:We used CoFe₂O₄@SiO₂@IRMOF-3 as an efficient catalyst and methanol as solvent for the synthesis of functionalized dihydro-2-oxopyrroles in a one-pot,four-component reaction of a dialkyl acetylenedicarboxylate,an aryl amine,formaldehyde,and optionally a second amine at room temperature.The catalyst not only exhibites higher activity but also shorten the time and achieve higher yields.CoFe₂O₄@SiO₂@MOF-5 as an magnetically recoverable catalyst and water as solvent were used to synthesize 3,4,5-substituted furan-2?5H?-ones in a one-pot three-component reaction of a dialkyl acetylenedicarboxylate,aryl amine,and aromatic aldehydes at room temperature.Next,we examined the substrate scope and limitations of this three-component reaction under the optimized conditions.A series of 3,4,5-substituted furan-2?5H?-ones were obtained in short time and high-yield.A novel and effective method was explored for the synthesis of 1,3-oxazines via the reaction of dialkyl acetylenedicarboxylate,aryl amine,and formaldehyde by using CoFe₂O₄@SiO₂@Cu-BTC as an efficient and recyclable catalyst and ethanol as a green solvent with so many advantages such as short time,good yield,and in keeping with the conception of green chemistry.