Application Of Porous Organic Polymers In Photocatalytic Organic Tandem Reactions

The rapid development of the society is inevitably accompanied by increasingly severe environmental pollution and resource depletion.It is of epoch-making practical significance to explore how to balance the relationship between social development,environmental protection and green and sustainable energy.Trying to explore green,efficient and sustainable new energy is the top priority of human survival and development.Hydrogen energy has become one of the most potential clean energy sources in the 21st century due to its characteristics of high heat and low pollution,and has gradually attracted extensive attention of researchers.It is of practical and theoretical importance and significance to take advantage of hydrogen energy more efficiently or convert it to other high value-added chemicals.Porous organic polymers（POPs）,as a new type of porous materials,exhibit great promise in the field of photocatalysis（such as photocatalytic hydrogen evolution,photocatalytic organic reactions,etc.）because of their excellent photoelectric properties,structural diversity and tunability.Therefore,this study innovatively proposes to combine the photocatalytic hydrogen production with the photocatalytic organic reaction in one-pot,realizing the efficient utilization of hydrogen through the in-situ reaction.We mainly employed the Schiff base reaction,Knoevenagel condensation reaction and Aldol condensation reaction to prepare a series of new covalent organic porous polymers with different linkages,and carried out in-depth and systematic research on the photocatalytic hydrogen evolution tandem nitrobenzene reduction reaction,which mainly includes the following main content:（1）A novel covalent organic framework material（ETTA-BDF-COF）based on the imine linkage of benzodifuran units and tetrastyrene units was designed and synthesized.The excellent crystallinity,physical and chemical stability and good optoelectronic properties were confirmed by a set of characterizations,such as powder X-ray diffraction,solid-state nuclear magnetic resonance etc.The maximum hydrogen evolution rate of the COF material is 680.32μmol g^-1 h^-1under visible-light irradiation,and its use in photocatalytic hydrogen evolution tandem reaction was tried and studied.（2）A series of novel vinyl-linked covalent porous organic polymers were designed and synthesized.First,a series of fluorine-functionalized POP materials were successfully synthesized by Knoevenagel condensation reaction,and their structures and properties were systematically characterized by means of XPS,solid-state NMR and FT-IR.The effect of fluorine content on the hydrogen production efficiency was explored in detail via photocatalytic water-splitting reactions,and the application of such materials in photocatalytic tandem reactions was systematically studied.（3）A novel fully conjugated vinyl-bridged covalent organic framework material（TMT-BT-sp²c-COF）was designed and characterized by powder X-ray diffraction,Fourier transform infrared spectroscopy,scanning electron microscopy and thermogravimetric analysis.The photocatalytic hydrogen evolution together with the in-situ reduction experiments were carried out and studied in detail.Remarkably,the conversion rate of nitrobenzene can reach 95%with excellent reusability and stability.