Ball Milling Synthesis Of Covalent Organic Framework And Catalytic Performance

Covalent organic frameworks(COFs)are a new class of porous crystalline organic polymer with periodic arrangement,adjustable pore size and designable structure.COFs have been widely used in environment,energy,medicine,and other fields.The main method to synthesize COFs is solvothermal method,which requires harsh conditions.It is still challenging to prepare COFs using green and convenient methods.The ball milling method is a green and environmentally friendly preparation method based on solid-solid reaction.It has the potential application value of large-scale production.In this study,three kinds of COFs composite materials were prepared by ball milling and the interaction mechanisms with organic pollutants were jointly investigated through characterization and experiment.This study hopes to provide new ideas for the design and synthesis of COFs materials.The main conclusions are as follows:(1)The COFs photocatalyst(TpMA)with a ternary structure of“triazine group active center-photo-electron shift platform-electron withdrawing unit”was designed and synthesized by ball milling method,exhibiting good mesoporous structure and excellent thermal stability.Sulfathiazole with a concentration of 120 mg/L could be completely degraded by TpMA catalyst within 45 min under visible light irradiation.The rate of photo-degradation was 0.1498 min^-1,which was more than three times that of TpMA prepared by solvothermal method.In addition,TpMA still has high stability and strong anti-interference ability in cellulose wastewater and polyvinyl alcohol(PVA)wastewater.(2)A composite catalyst(Au@TpMA)with ultrafine Au NPs supported on COFs was prepared using COFs as excellent support and stable frameworks to limit the growth of gold nanoparticles(Au NPs).The content and diameter of Au NPs on the surface of COFs can be controlled by adjusting the amount of precursor.Au@TpMA catalyst has the characteristics of low dosage,efficient reduction of 4-nitrophenol,and high conversion rate in a short time.(3)The magnetic COFs-based composite(Fe₃O₄@TpMA)with superparamagnetic properties was prepared by mixing and grinding magnetic nanoparticles and COFs through ball milling method.Fe₃O₄@TpMA catalyst exhibited a higher degradation rate for methyl orange than single materials(e.g.Fe₃O₄ and TpMA)and mixed materials(e.g.Fe₃O₄+TpMA)under the activation of H₂O₂.The degradation mechanism is dominated by the heterogeneous reaction mechanism,and supplemented by the homogeneous Fenton reaction mechanism.(4)As a low-cost,flexible and simple preparation method based on solid-solid reaction,the ball milling can be used to prepare a single COFs material and COFs-based composites.It provides a new path for the preparation and modification of COFs,as well as a new idea for preparing organic-inorganic hybrid materials by ball milling.