MOFs With Multi-aromatic Ring Structural Organic Ligands Applied In Selective Adsorption And Photo/Electroreduction Catalysis For CO₂

Metal-organic framework（MOF）is a new type of porous material,composed of secondary building units（metal ions or metal clusters）and organic ligands,with a high specific surface area,easily tunable pore structure and dense catalytic active sites.At present,MOF materials usually undergo a catalytic reduction reaction in a pure carbon dioxide atmosphere.In this thesis,we investigated MOFs with parallel multi-aromatic ring structural organic ligands applied in selective CO₂ adsorption and the photo/electrocatalytic reduction in a mixed atmosphere with a low CO₂concentration.2,4,6-tri（4-carboxyphenyl）-1,3,5-triazine with abundant N atoms,strong optical active1,3,6,8-tetra（4carboxyphenyl）pyrene and highlyπ-conjugated 5,10,15,20-tetrakis（4-（1H-imidazol-1-yl）phenyl）porphyrin,the three organic ligands were selected to design and synthesize MOF materials with different structures and enhance the photo/electrical reduction activity and selectivity of materials.We investigated CO₂adsorption and photo/electroreduction catalytic performances of these materials,especially the catalytic reduction activity in a mixed atmosphere.The specific work is as follows:（1）Cu-TATB was synthesized by hydrothermal method using 2,4,6-tri（4-carboxyphenyl）-1,3,5-triazine as an organic ligand.Two different pores of Cu-TATB are formed in space,one is an open channel,and the other is an octahedral cage channel.The open channel is conducive to gas transmission,and the cage channel is easy to capture and separate CO₂ molecules.Therefore,Cu-TATB shows good selectivity for CO₂ adsorption.At 298 K and 1 atm,the adsorption capacity of CO₂ is 59.04 cm³/g,while the N₂ adsorption capacity is 8.40 cm³/g.And the selectivity reaches 27 in the mixed gas of N₂/CO₂（50/50,V/V）.（2）Two MOFs（Co-TBAPy and Cu-TBAPy）with different structures was synthesized by the coordination of 1,3,6,8-tetra（4-carboxyphenyl）pyrene with different transition metal salts(Co²⁺,Cu²⁺).Among them,two-dimensional layered Co-TBAPy showed high photocatalytic activity for CO₂ reduction after ultrasonic stripping,and the yield of HCOOH reaches 5.88 mmol/g within 10 h,which can stabilize the catalytic activity for 30 h.Even under the simulated fuel gas conditions（CO₂:14.7%）,the yield of HCOOH still reaches 4.83 mmol/g within 10 h.Cu-TBAPy can reduce CO₂ to formic acid,and the FE_HCOOH is 78.9%at-1.1 V（vs.RHE）.MOFs with pyrenyl derivatives as ligands can be well used in both photocatalytic and electrocatalytic fields.（3）The porphyrin-based derivative modified by imidazole group has great CO₂adsorption performance and electron transfer ability.Ni-TIPP with two-dimensional interpenetrated structure was synthesized by using 5,10,15,20-tetrakis（4-（1H-imidazol-1-yl）phenyl）porphyrin and nickel acetate.The MOF has good CO₂ adsorption performance and electrocatalytic reduction performance.At 273 K,the CO₂ adsorption capacity is 20.19 cm³/g.Ni-TIPP exhibits Faradaic efficiency for CO about 80.1%at-1.0 V（vs.RHE）.