The Design And Synthesis Of Three-dimensional COF Materials And Electrocatalytic Nitrogen Reduction To Produce Ammonia Based On Metalloporphyrins

As we all know,metalloporphyrin molecules have many unique functional characteristics due to their diverse ligand porphyrin structures and easy adjustment of central metal ions.They have shown huge research and application prospects in many frontier fields such as optoelectronic optical detection,biological imagination,porous framework materials,catalysis,etc.In this paper,with specific metal porphyrin compounds as the basic unit,detailed research and exploration have been carried out in the field of the construction of three-dimensional covalent organic framework materials(COFs)and the electrocatalytic reduction of nitrogen to produce ammonia,as showing follows:First,the construction of the three-dimensional COFs based on metalloporphyrins was designed and verified in detail.Metalloporphyrin molecules with amino groups were condensed with terephthalaldehyde to form corresponding two-dimensional COFs,and then the metal ions in the center of the internal porphyrin ring were complexed with liner molecules containing lone pair of electrons at both ends to form a three-dimensional COFs.The results showed that the optimal conditions for this reaction were used 4,4-bipyridine as the "supporting column",acetonitrile and distilled water(volume ratio 1:1)as the solvothermal reaction solvent,in a sealed tube at 100? and prepared in advance two-dimensional metal porphyrin COFs were allowed to react together for 72 h.The corresponding characterization results showed that the final material was not a uniform and regular three-dimensional morphology,only a small part of the metal porphyrin two-dimensional COFs was converted into the corresponding three-dimensional COFs.The entire experimental design circuit and synthesis method need to be further optimized and adjusted.Secondly,by introduced different central metal ions and side chain substitution groups,a series of metalloporphyrin molecules were designed and synthesized,and then their catalytic efficiency in electrocatalytic nitrogen reduction ammonia product-ion experiments was investigated in detail.The experimental results showed that the cobalt porphyrin molecule with a methoxy group substitution had the highest Faraday efficiency(32.07%)and the highest average ammonia yield(1.067 ?gNH3 mgcat.-1 h-1)in the ammonia production process with nitrogen reduction at a voltage of-0.24 V(vs.RHE),The reason for this phenomenon was mainly due to:1)when the cobalt porphyrin molecule with methoxy substituent was used as an electrocatalyst,the hydrogen evolution reaction efficiency as the competition reaction during the nitrogen reduction process was the weakest;2)compared with other substituent groups,when methoxy was used as a substituent,the corresponding metal porphyrin molecule had the most suitable steric hindrance for electrocatalytic reduction of nitrogen to produce ammonia.This strategy of influencing electrocatalytic nitrogen reduction and ammonia production through substitution groups may provide a new perspective for the application and development of metalloporphyrins in the field of catalysis.