Design, Synthesis And Photocatalytic Activity Of Boron-doped Carbon Nitride-based Nanomaterials For Alcohol Oxidation

Solar power under the atmospheric pressure of O₂ as oxidant alcohol selective oxidation reaction,to produce aldehyde ketone and so on product is one of the most ideal reaction path,however,achieve highly active or selective conversion process is still a big challenge,the key lies in how to preparation for alcohol oxidation and O₂activation of photocatalytic materials.Graphitic carbon nitride（g-C₃N₄）,a non-metallic polymer,has visible light response,stable properties and a high conduction band position conducive to the reduction of O₂.It has been proved that it can effectively activate O₂ to produce reactive oxygen species for selective oxidation of alcohol.However,the low oxidation capacity of g-C₃N₄ valence band,poor charge separation and lack of catalytic sites to activate O₂ still limit the photocatalytic oxidation performance of g-C₃N₄.Therefore,in this paper,boron doped carbon nitride（BCN）ultrathin nanosheets were prepared to regulate their energy band structure,and heterojunctions were constructed based on BCN to improve charge separation,and catalytic sites for activating O₂ were introduced to comprehensively realize the photocatalytic selective alcohol oxidation with high activity and selectivity.In particular,the following two work have been carried out:（1）Nickel phthalocyanine（NiPc）-Iron phthalocyanine（FePc）/BCN Z-scheme heterojunction materials were constructed for selective oxidation of high efficiency alcohols.Firstly,g-C₃N₄ nanosheets were mixed with Na BH₄ and calcined to prepare B-doped g-C₃N₄（BCN）with more suitable energy band structure for alcohol oxidation.Then,J-type aggregates of subnanometer NiPc-FePc were assembled on BCN through H bond interaction,and a new NiPc-FePc/BCN Z-scheme heterojunction with matching size was obtained.By changing Ni:Feratio,the optimum NiPc-FePc/BCN photocatalyst can greatly improve the oxidation conversion of benzyl alcohol under visible light conditions,and the selectivity of benzaldehyde is close to 100%.Experimental and theoretical results show that the Z-scheme electron transfer in NiPc-FePc/BCN series promotes charge separation.At the same time,theoretical calculation and experimental results show that the synergistic effect of NiPc and FePc promotes the catalytic reduction of O₂ to produce reactive free radicals,and leads the selective oxidation of BA together with the holes produced by BCN.This study provides a new Z-scheme photocatalytic system for green organic synthesis.（2）BCN modified by Iron oxide（FeOOH）species for efficient selective oxidation of alcohols.Inspired by the activation of O₂ by Fe,the central metal of FePc,the activation of O₂ by FeOOH was used to promote the charge separation ability of BCN.The highly dispersed ferric species（Fe-BCN）were modified on BCN by freeze-drying method.Fe-bcn with 1%Femodification increased the yield of benzaldehyde to 1054.7μmol g^-1 h^-1,and the selectivity was close to 100%.The O₂-temperature programmed desorption curve shows that the adsorption and activation capacity of Fe-BCN is greatly improved,and^·O₂^-free radicals are generated by electrons,thus promoting charge separation and prolonging the life of the hole,thus greatly improving the oxidation capacity of benzyl alcohol.