Effect Of Metal Ionicsubstitutionon Stability And Gas Adsorption For D¹⁰ MOFs

The emerging microporous Metal-organic frameworks?MOFs?are promising ascost-effective and efficient materials for gas adsorption and separation,fluorescence detection,proton conductivity and catalytic due to their high specific surface area,high porosity and structural designability.The MOFs with novel structure constructed by the d¹⁰Zn²⁺ and Cd²⁺ could be synthesized easily,but the disadvantages of low coordination orientation and insufficient rigidity of the metal nodes restrict their application.In order to solve this problem,we choose thenon d¹⁰ transition metal ions to replace the Zn²⁺ or Cd²⁺in the metal nodes,so as to enhance the coordination orientation and the rigidity of the metal nodes.Firstly,we synthesized tetra nuclear FJU-61 and FJU-62.FJU-61 with Al₂O₃ topology was constructed by triangular tetra-nuclear Cd and H4ttpm based on 4,6-connected mode,In FJU-62,a chain with tetranuclear cadmium and H4ttpm through 4.6-connection mode to form a three-dimensionalframework material.Four mixed metallic MOFs:FJU-61-Cu?FJU-61-Co?FJU-62-Cu and FJU-62-Co were obtained by replacing Cd²⁺ through non d¹⁰ Cu²⁺ and Co²⁺.All of Cd²⁺coordinating with solvents in FJU-62 was substituted by Cu²⁺ to get FJU-62-Cu,however,only Cd²⁺coordinating with four solvents was replaced by Co²⁺ to get FJU-62-Co,which showed that the substitution ability of Cu²⁺ is stronger than that of Co²⁺ and the more coordination solvents are,the more easier the substitution reaction occurs.Compared with the FJU-61 and FJU-62,which have no stable pore structure,the BET surface ofFJU-61-Cu,FJU-61-Co,FJU-62-Cu and FJU-62-Coincreased significantly,whichis 369.72 m2 g-1?304.59m2 g-1?423.02 m2 g-1 and 113.50 m2 g-1 espectively.The IAST selectivity of FJU-61-Co and FJU-62-Co for 15:85 CO2/N2is high,which is 103.54 and 102.57 respectively.In addition,we synthesizedFJU-60,in which4-connected H4ttpm was bridged by8-connected octanuclear Zn,forming a 3D framework with flu net,and obtained four mixed metallic MOFs by metal metal ion substitution.The band gap of the substituted FJU-60-X was 2.17?Co?,2.78?Cu?,2.69?Ni?and 2.71?Ru?eV,which wa significantly lower than FJU-60?3.05?,indicating that metal substitution can effectively regulate the band gap of MOFs.The catalystic activity of FJU-60-1000 being pyrolysised at 1000 ?,whose onset potential and number of transferred electrons is-0.185 V and 3.92,is good.However,the electrocatalytic oxygen reduction performance of the pyrolysis products of metal substituted FJU-60-X was significantly poor,indicating that the metal substitution reaction on the MOFs node could not effectively improve the electrocatalytic properties of ORR.