Construction And Catalytic Carbon Dioxide Conversion Of Tetracarboxylic Acid Based Metal-organic Frameworks

Metal-Organic Frameworks(MOFs),as a kind of crystalline porous materials,could be a new kind of arising catalysts due to their high porosity,large surface area and contrivable,modifiable and tunable inner cavities through the different selection of constructive units.On the other hand,environment issue has become an obstruction for the human development.The conversion of carbon dioxide to valuable fuels or chemicals,achiving the utilization as a resource,not only could mitigate the green house effect,but also benefit for the equilibrium of natural carbon resource.Based on these considerations,it is highly desirable and significant to design new MOFs materials with high activity,selectivity and stability for carbon dioxide catalytic conversion.In this paper,we have employed a series of porous MOFs catalysts through the coordination-oriented assembly between the active transition metals and ?-conjugate tetraphenyl ethylene and porphyrin tetracarboxylate units,which are chemically stable and easy-modified to exhibit diverse structures.According to the catalytic mechanism of MOFs materials,new types of heterogeneous catalytic systems have been developed and the catalytic conversions of carbon dioxide have also achieved in a high yield and selectivity.(1)Through hydrothermal method,a discrete metal-organic nanotube Ni-TCPE1 has been synthesized by incorporating of the tetrakis(4-carboxyphenyl)ethylene moiety and Ni2+ions with an interior channel diameter of 21 A,representing the largest discrete single-walled metal-organic nanotube reported to date.The cycloaddition of carbon dioxide to epoxides to produce cyclic carbonates has been employed in heterogeneous state,and the results indicate that cooperative weak interactions were existed between the inner cavity of Ni-TCPE1 and substrates.Meanwhile,the large cavity could decrease the restriction of substrates,achieving the activation of epoxides under the synergy of opening metal sites.(2)By incorporating tetrakis(4-carboxyphenyl)ethylene moiety with active Ag+ ions endowing the specific alkynophilicity,a three-dimensional framework Ag-TCPE has been synthesized.It contains large quadrilateral channels of 15.4 × 15.4 A2 along the c direction and decentralized Ag chains with unsaturated sites along the inner walls.Ag-TCPE represents an efficient catalytic capability in a heterogeneous manner for the carboxylative cyclization of propargylic alcohols with carbon dioxide and afforded 99%conversion.Moreover,effectively utilize the alkynophilicity of Ag+ centers of Ag-TCPE to ?-activation and ?-activation of the substrates enables successful tandem conversion of the phenyl-acetylene and carbon dioxide to a-alkylidene cyclic carbonates in a single-system catalysis reaction.(3)To develop the regulate functionality of ligands,the incorporation of excellent photocatalytic porphyrin units and Ni2+ ions has obtained a three-dimensional framework Ni-TCPP(Ni)with large channels of 32 A.The photocatalytic conversion of carbon dioxide into formate anion has been achieved through the synergy effect of light-harvesting units and metal clusters.Introduce fac-Ir(ppy)3 as photosensitizer into the system could regulate the light absorption ability and effeciency of the system.A isostructural Ni-TCPP(Ir)has been further synthesized using TCPP(Ir)ligands and the influence of metal ions to the light transfer of catalyst has also been investigated.