| Metal-Organic Frameworks(MOFs),are an emerging class of crystalline porous materials formed by the self-assembly of organic bridging ligands and metal ions or metal cluster,which have been widely studied in adsorption,separation,catalysis,luminescence,induction,etc.Common inorganic secondary building units in MOFs include octahedral hexa-carboxyl tetra-nuclear cluster,tetragonal paddle-shaped tetra-carboxylic di-nuclear cluster,trigonal prismatic hexa-carboxylic tri-nuclear cluster and cubic octahedron twelve-carboxyl hexa-nuclear cluster.The coordination number of trigonal prismatic hexa-carboxylic trinuclear cluster unit represented by MIL-100 can be increased from 6 to 9,which not only enrich the structure type but also improve the stability of the material.The metal of the blocking unit can be either a transition metal(scandium,vanadium,chromium,iron,cobalt,nickel,etc),or an alkaline-earth metal(magnesium)and a main group metal(indium),or even some mixed metals,which greatly broaden the function of the materials.In addition,the blocking unit can easily produce empty metal coordination site which is favorable for adsorption and catalysis,and the properties of pore surface can be modified by coordination modification.Herein,10 kinds of MOFs with different structures were successfully synthesized by solvothermal method in the premise of tri-nuclear nickel cluster as the blocking unit.The main works are summarized as follows:1.3,5-di(4-carboxylphenyl)benozoic acid(DCPB)and tri-prismtri-nuclear nickel cluster[Ni3O]were chosen to assemble the compounds with three-dimension malleable structure which contains both large and small cage cavities.By introducing pyridine(Py)or its derivative molecules(amino and carboxyl functionalized,such as AP,IA)on the axial site of blocking unit,the surface of the inner pores can be well modified.For these modified materials[Ni3(μ3-O)(DCPB)2(X)3](X=Py,IA,AP,IA/AP)(1-4),the chemical stability is greatly improved,and it also exhibits better CO2/N2 adsorption selectivity.2.By selecting Terphenyl-3,3",5,5"-tetracarboxylic acid(TPTC)and isonicotinic acid as the bridging ligands,we synthesized two MOFs with different topological structures,[Ni(TPTC)(H2O)2]4·H2O](5)(NbO type)and[Ni3(TPTC)(IA)2(μ2-H2O)2(CH3OH)2](6)(the Schlafli symbol is{32.42.52}{34.46.58.68.72}),via solvothermal method.Compound 6 possesses higher chemical stability and higher CO2/N2 selective adsorption performance than compound 5.3.We used 4,4-sulfonyl dibenzoic acid(DABO)and 2,4,6-tri(4-pyridyl)-1,3,5-triazine(TPT)to synthesize two compounds with different dimensions,[Ni3(μ3-O)(DABO)3(TPT)2(H2O)](7)and[Ni3(μ3-O)(DABO)1.5(CH3COO)3(TPT)]·C3H9N(8).The two-dimensional compound 8 has higher chemical stability and larger specific surface area than one-dimensional compound 7.4.Two distinct compounds with dissimilar topology,[Ni3(μ3-O)(TCPE)5(Py)3(9)and[Ni3(μ3-O)(TCPE)4(PBA)4(H2O)]·0.5(C2H7N)](10),were synthesized with tetra(4-carboxyphenyl)ethylene(TCPE)and pyridine(Py),4-pyridyl-4-phenylbenzoic acid(PBA),respectively.In comparison,the 4,6-connected compound 9 has a larger cavity and greater adsorption capacity for CO2,but 4,8-connected compound 10 exhibits higher stability. |
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