Preparation And Catalytic Performance Of Porous Carbon Nitride Materials

Polymerized carbon nitride（PCN）is a kind of metal free semiconductor material,which has good chemical stability and thermal stability,non-toxic,rich raw materials and easy preparation.It also has visible light absorption,appropriate conduction band valence band position and tunable electronic properties.However,the practical application of carbon nitride is still restricted by the problems of fast recombination speed,small specific surface area and limited visible light absorption.Therefore,the preparation of carbon nitride semiconductor materials with high specific surface area and high crystallinity is of great significance in the field of catalysis.The catalytic conversion of fossil resources or the use of green solar energy for the production of fine chemicals and drug molecular components has always been a challenging topic.Due to its unique electronic structure and semiconductor properties,carbon nitride can not only coordinate with metals for thermal catalysis to produce various drug molecular products,but also use solar energy to produce green hydrogen energy for the reduction of olefins to prepare related fine chemicals Fine chemicals.However,the low specific surface area and poor crystallinity of carbon nitride still hinder its high catalytic application.Therefore,the preparation of porous crystalline carbon nitride with high specific surface area is the focus of this paper.The work of this paper is mainly described from the following three aspects1.Porous carbon nitride supported copper nanotubes（Cu/PCN-MNT）were prepared by self-assembly of Cu（NO₃）₂·3H₂O and melamine without template.Scanning electron microscopy（SEM）and transmission electron microscopy（TEM）images show that the material is composed of PCN nanotubes with a diameter of about 5-50 nm,and contains various mesoporous structures with a size of about 5-10 nm.The unique porous tubular structure has more active sites than the original PCN.N-（4-methoxyphenyl）pyrimidin-2-amine was obtained from the coupling reaction of pyrimidin-2-amine with 1-iodo-4-methoxybenzene in 62%yield.2.In order to expand the engineering application prospect of porous carbon nitride materials containing copper,based on the preparation of porous carbon nitride supported copper nanotubes（Cu/PCN-MNT）,the preparation process was scaled up to gram scale,the amount of precursor melamine was scaled up to 50 times,and the amount of Cu（NO₃）₂·3H₂O was scaled up to 40 times.TEM characterization showed that the catalyst was still porous and the size was about 50 nm.Taking the coupling reaction of n-methylpyrimidin-2-amine and 1-iodobenzene as the model reaction,the reaction conditions of 1 mmol small amount and the activity test of the catalyst were carried out.The yield of the product reached 82%and the related substrates were expanded.Finally,the yield of the product reached at least 60%when the amount of the template reaction substrate was 10 times and 50 times.In the cyclic reaction experiment,the catalyst can be used more than five times.It has a certain engineering application prospect.3.Although the specific surface area and thermal catalytic activity of porous carbon nitride containing copper were improved by composite method,the crystallinity of porous carbon nitride was found to be poor by XRD characterization,and its activity in photolysis of hydrogen by solar energy was still low,On this basis,CaCO₃ and KCl were used as hard templates to grind with melamine.The precursor was calcined at 580℃ for 4h,and then the CaCO₃ and KCl were washed away by dilute hydrochloric acid to obtain porous and crystalline carbon nitride（PPCN）.The performance test results show that the hydrogen production rate of PPCN is about 2.5 mol·g-1·h-1.The hydrogen production activity of KPCN is about 3 times higher than that of crystalline KPCN.After compounding with Pd particles,the material can be used for olefin hydrogenation reaction with water as hydrogen source at room temperature and atmospheric pressure.At the same time,hole oxidation is used to expand the alcohol substrate and produce valuable hydrogenation and oxidation products.Both hydrogenation and oxidation have good activity.