Preparation And Catalytic Performance Of Carbonaceous Catalysts Derived From Porphyrin Polymers

Porphyrin polymer is formed by connecting porphyrin and organic linker through various reactions or directly connected and polymerized during the synthesis of porphyrin.It has a rich pore structure,a large specific surface area,a stable structure and structural adjustability.Porphyrin polymer materials have attracted widespread attention in various fields,including o rganic catalysis,gas storage and separation,water oxidation,and electrochemical sensing.The porphyrin monomer and organic linker can be designed cleverly to achieve the predetermined effect,making it an ideal adjustable system.The porphyrin polymer c an be modified by its porosity,electron transport,and metal content adjustability.In recent years,carbon materials formed by pyrolysis of porphyrin polymers and their derivatives have been widely reported,showing great potential in the field of electr ocatalysis.The main content of this paper includes the following two parts:（1）Based on the porosity of the porphyrin polymer and the adjustability of the metal content,in this paper,a conjugated cobalt porphyrin porous polymer Co/PCP was synthesized by Suzuki coupling reaction and used as a precursor for controlled heat treatment under an inert atmosphere to prepare Metal-nitrogen-carbon catalyst Co₃O₄@PNC-x.The effect of heat treatment temperature on the performance of the catalyst was explored,and a series of characterizations of Co₃O₄@PNC-400 were carried out.The catalytic performance of Co ₃O₄@PNC-400 for the catalytic oxidation of toluene to benzaldehyde at 110 ^oC and 1MPa O₂ and the catalytic performance of the catalytic oxidation of cyclohexane to KA oil were studied.The experimental results showed that the conversion rate of the catalyst to oxidized toluene reached22%,the selectivity to benzaldehyde reached 85.9%;the conversion rate of cyclohexane oxidation was 16.5%,and the selectivity of KA oil was 90.5%.After the reaction,the catalyst was recovered,and it was found that the structure of Co₃O₄@PNC-400 remained stable,and its performance was not significantly reduced after repeated toluene oxidation experiments for five times.Based on the experimental results and literature reports,we proposed a possible reaction mechanism for Co₃O₄@PNC-400 to oxidize toluene.（2）Based on the principle of the Diels-Alder method to synthesize porphyrin,we skipped the step of synthesizing porphyrin an d directly synthesized the porphyrin conjugated microporous polymer CMP and the metal cobalt porphyrin conjugated microporous polymer Co-CMP in one step.Then the CMP was carbonized at a high temperature to obtain the metal-free carbon catalyst C-CMP-x（x represents the pyrolysis temperature）,and then a series of metal-free catalysts obtained from the pyrolysis are modified on a glassy carbon electrode for electrocatalytic oxygen evolution reaction（OER）.The experimental results show that C-CMP-900 exhibits very good electrocatalytic oxygen evolution performance in alkaline environment.The overpotential with a current density of 10 m A·cm^-2 is 370 m V（lower than the commercial Ru O₂ catalyst）,corresponding to the Tafel slope It is 47.5m Vdec^-1;after1000 cycles of testing,the overpotential only increased slightly.Finally,the electro-reduction of nitrobenzene was carried out on the C-CMP-900 catalyst,which showed a very low limit of detection.The detection limit of nitrobenzene was 0.015u M;within the test range,Compared with the literature,C-CMP-900 has a higher sensitivity,reaching 2.75 u A/u M.