| Metal-organic frameworks(MOFs),constructed by the metal contained secondary units and organic bridging ligands in the form of coordination bonds,are a series of crystalline organic-inorganic hybrid materials,which possess permanent pores.The structural composition determines its superiority on porosity,uniform channel,crystallinity and flexible structures,which have been applied for gas absorption,separation,sensing,drug transport,catalysis,and so on.Amongst them,photocatalysis is a relatively new and popular field.The MOF is considered to be a highly ordered arrangement of electron donors and acceptors.After photo excitation,the charge separation state will be formed,which is the basis of the application of MOF to photocatalysis.Combined with the highly flexible and adjustable structure characteristics of MOF,it has become a high-quality research object to explore the structure activity relationship in photocatalysis process.The large-scale use of fossil fuels has brought global energy crisis and environmental problems.Searching for clean and sustainable alternative energy has been an urgent demand for the rapid development of society,which has attracted the attention of researchers.Photocatalytic water splitting has always been considered as a measure to solve the dilemma.However,the process of the industrialization of overall water splitting is still obstructed.On the one hand,the efficiency of overall water splitting is inhibited by the high dynamic impediment of the half-reaction of water oxidation.On the other hand,the product oxygen is not only in low-value,but also leads to the trend of inverse reaction.This also requires the timely separation of products in the catalytic process,which aggravates the cost of photocatalysis.Based on the above points and existing former experiences in the laboratory,we start our work as follows:(1)we chose the MOF composite(Pt/PCN-777)containing s-triazine as the building strut to replace the oxidative half reaction of oxygen production with a higher valued benzylamine oxidation.The generated hydrogen is left in the gas phase,and the product of the oxidation of benzylamine remains in the liquid phase,which realizes the separation of the products and inhibits the inverse reaction,and then improves the overall efficiency of the reaction.(2)through the electrochemical characterization,we reveal the mechanism of the reaction,that is,after photo-excitation,the electrons in PCN-777 are quickly transferred to Pt cocatalyst.The Pt reduced the proton to produce hydrogen,while the hole oxidized benzylamine to generate benzylamine cationic radical,which will be further converted into N-benzylbenzaldimine.(3)through the characterization of photoelectrochemistry and theoretical calculation,we demonstrated that the s-triazine group plays an important role in promoting the efficieny of charge separation among the MOF composite,thus improving the overall activity.This paper is based on the basic understanding of MOF based photocatalytic materials.Through the continuous exploration of the correlation between the intrinsic properties of MOFs and the catalytic performance,the feasibility viewpoint and scheme for future in-depth application are further developed,which will be enlightening to the fields of catalysis and materials in the future. |
