Design,Preparation And Properties Of Functional Materials Based On Metal-organic Cages

Metal-Organic Cages（MOCs）are nano-sized,discrete（zero-dimensional）molecularassemblies formed by coordination self-assembly of metal ions and organic ligands.Because of its definite and adjustable atomic number,spatial configuration and size,MOCs have been widely used in catalysis,gas storage and separation,sensing and other fields.However,the close-packed structure of a single MOC will lead to mass transfer limitation,and the intrinsic performance of MOCs can not be fully exerted.Therefore,it is of great significance to select suitable carriers to achieve high spatial dispersion of MOCs and build high-performancefunctional materials based on MOCs.In this work,the tetrahedron MOCS:Co₄（LBA）₆（Cl O₄）₈(Co-LBA,LBA=[1,1’-biphenyl]-4,4’-diamine,N₄,N₄’-bis（2-pyridinemethylene）is formed by self-assembly of a bidentate organic ligand formed from benzidine and pyridine formaldehyde.Two kinds of r GO hybrid materials based on MOCs functionalization are obtained by using the electrostatic interaction between them to realize controllable assembly and derivatization,and theirperformances in selective separation of alkene/alkyne and catalytic oxygen reduction reaction are systematically studied.The main research results are as follows:（1）MOCs:Co-LBA with a window size（4?）between the kinetic diameters of acetylene（3.34?）and ethylene（4.18?）is synthesized.It is further dispersed on graphene oxide（GO）substrate by impregnation method,and a Co-LBA functionalized graphene material withhierarchical structure（Co-LBA@r GO）is obtained by calcination.In the Co-LBA@r GOcomposite,the Co-LBA keeps a cage structure and is highly dispersed among graphene layers,which makes the material have both microporous and mesoporous molecular diffusionchannels.Co-LBA@r GO shows remarkable selective adsorption capacity for acetylene under the synergistic effect of micropore selectivity for ethylene/acetylene separation andmulti-stage diffusion channels.When P/P₀is 0.5,the adsorption ratio of acetylene to ethylene reaches 12.5,which shows a potential application prospect for ethylene/alkyne separation.（2）Co-r GO,a supported Co-sub-nano cluster catalyst,is successfully prepared by using Co-LBA as the precursor and the matching of the structure between the precursor and thetarget sub-nano cluster.XRD,SEM,TEM and HADDF-STEM are used to characterize its structure and morphology,which confirmed the successful synthesis of sub-nano cluster catalyst Co-r GO.The electrocatalytic oxygen reduction performance of Co-r GO isinvestigated by LSV,CV and other electrochemistry.The half-wave potential of Co-r GO is0.82 V,and the number of transferred electrons is 3.84,which is close to the four-electron transfer path.Co-r GO material also shows good cycle stability.