Synthesis Of Metal-Organic Compounds And Selective Hydrogenation Performance Of ?,?-unsaturated Aldehyde Over MOF-Derived Materials

The selective catalytic hydrogenation of a,P-unsaturated aldehydes is common in the industrial production of fine chemical products and has been receiving widespread attention.Among them,citral has a series of possible reaction pathways because of its many functional groups,so the product is more complicated.Carbon-oxygen double bonds have higher activation energy than carbon-carbon double bonds,so hydrogenation of carbon-oxygen bonds is very challenging.When carbon-carbon double bonds are linked or conjugated with other substituents(such as benzene rings,furan rings,etc.),selective hydrogenation of carbon-carbon double bonds becomes challenging due to steric hindrance and electronic effects.The selective hydrogenation of carbon-carbon double bonds is also a research hotspot.Metal-organic Frameworks(MOFs)are a new kind of porous solid materials,which are formed by bridging metal ions or metal clusters with organic ligands.In the past two decades,it has attracted widespread attention,especially one of the applications of MOFs and their derivatives in the field of catalysis.In this paper,two V-type pyrimidine nitrogen-rich ligands were designed and prepared,and five new metal-organic framework compounds were synthesized by using them and a series of carboxylic acids and metal salts.Its structure and physical and chemical properties were characterized accordingly,and some applications of MOFs in catalysis were explored.The main contents are as follows:1.Two new nitrogen-rich ligands,bem and be2am,were reacted with different carboxylic acids and metal salts to synthesize 5 new metal-organic compounds.The bem and terephthalic acid solvothermal method produces compound 1 with a double-penetrated pcu topology.Under similar synthetic conditions,replacing isophthalic acid with isophthalic acid gave zero-dimensional compound 2 with Lewis acid-base sites.An amino group was introduced into the nitrogen-rich ligand,and two three-dimensional MOFs(compounds 3 and 4)with the same structure were synthesized using this ligand and phthalic acid,respectively.Compounds 3 and 4 have abundant uncoordinated nitrogen atoms and also have a large specific surface area.Coordination of be2am with the longer carboxylic acid H2bpndc yields compound 5,which is a metal-organic nanotube with a one-dimensional structure,and its internal pore diameter can reach 1.76 nm.2.Co@CN-X(X is the calcination temperature)catalyst prepared by pyrolysis of compound 4 as a precursor under nitrogen atmosphere,and its catalytic performance for selective hydrogenation of citral was investigated.The results show that the catalyst Co@CN-700 has good catalytic performance for the selective hydrogenation of citral.At 100?,2 MPa,and 90 minutes,the conversion rate reached 97.8%,and the yield of unsaturated alcohols reached 68.3%,and has good cycle stability.In addition,the catalyst can be easily separated using an external magnetic field,and can be reused multiple times without significant loss of catalytic efficiency.3.Using compound 4 as a carrier,a supported catalyst Pd(X)/MOF was prepared by the impregnation method,where X is the supported amount.The Pd nanoparticles were about 3.3 nm after loading,and reached 4.05 nm at 3 wt%loading.The catalytic performance of cinnamaldehyde hydrogenation shows that Pd(2)/MOF has the best activity.At 40?,1 MPa,and 70 minutes,the conversion rate reaches 100%,the selectivity reaches 80.2%,and the catalyst can be recycled.4 Times.