The Modification And Visible-light-driven Photocatalytic Performances Of Covalent Triazine Frameworks

Covalent triazine frameworks(CTFs)as one of the typical covalent organic frameworks(COFs),which is composed of triazine units,thus offering them with high chemical and thermal stability,was regarded as a promising photocatalytic material.Nevertheless,the photocatalytic activity of CTFs is seriously limited by short charge carrier lifetime and insufficient sunlight absorption,which greatly inhibited its potential photocatalytic applications in energy and environment-related applications.In this work,covalent triazine framework(CTF-T1)has been synthesized by the terephthalonitrile trimerization reactions.And then,the as-prepared CTF-T1 sample was further modified in order to obtain more efficient photocatalytic materials.The physicochemical properties of the samples were characterized in detail.The photocatalytic activities of the as-prepared samples were evaluated by the photocatalytic sterilization,photocatalytic degradation of Rhodamine B and photocatalytic water splitting into hydrogen.Our main works include as follows:(1)the fabrication of Ag/AgBr/CTF-T1 ternary heterstructured composite,and the mechanism of the enhancement of photocatalytic sterilization activities.(2)The photo absorption of the noble metal loaded CTF-TI sample,and the mechanism of the enhancement of photocatalytic hydrogen production activities.(3)The correlations among the structures,photoelectric properties and photocatalytic hydrogen production activities on carbon quantum dots(CQDs)loaded CTF-TI composite photocatalyst.The main results and conclusions obtained from the present research are as follows:(1)Ag and AgBr were successfully deposited on CTF-TI through a simple deposition method and photoreduction method.Ag/AgBr/CTF-T1 was explored as a photocatalyst for both photocatalytic sterilization(Escherichia coli and Staphylococcus aureust)and degradation of rhodamine B.The photocatalytic sterilization activities of the CTF-T1 samples were greatly enhanced after depositing Ag/AgBr under visible light irradiation.This could be ascribed to the separation efficiency of photoexcited electrons and holes.The active species detection experiments indicated the h+,·OH,·O2-and H2O2 are the main species in the photocatalytic sterilization process.Moreover,Ag/AgBr/CTF-T1 composite showed a rhodamine B degradation rate of 100%within 80 min.(2)Ag,Au and Pt nanoparticles loaded CTF-T1 photocatalysts were prepared via the sodium borohydride reduction method,respectively.The photocatalytic hydrogen evolution activity of CTF-T1 was effectively improved after loading noble metals.The Pt-loaded CTF-T1 photocatalyst show much higher photocatalytic hydrogen evolution activity than the Ag-loaded CTF-T1 and Au-loaded CTF-T1.When the loaded contents of Pt was 3 wt%,the photocatalytic hydrogen evolution activity of the sample reached maximum.(3)Carbon dots loaded on the surface of CTF-T1 has been successfully prepared through an impregnation process,which displayed much higher photocatalytic activitiy for photocatalytic water splitting into hydrogen compared to the pristine CTF-T1.Notably,the highest photocatalytic activity obtained at C0.24/CTF-T1 is about 3 times higher than that of pristine CTF-T1 sample.The rate of hydrogen evolution reaches 2.0 ?mol h-1.The photocatalytic activity enhancement is mainly due to the low recombination of eletron-hole pairs inhibited by carbon dots effectively.