Synthesis And Photocatalytic Properties Of β-Ketenamine Covalent Organic Framework

Covalent organic frameworks（COFs）are a promising semiconductor photocatalysis material with a numbe r of unique properties,including an adjustable bandgap,π-πstacked structure,excellent visible light sensitivity（400-700 nm）,high specific surface area,high carrier mobility,superior p hysical and chemical stability,etc.It is widely used in the fields of pollutant deg radation,organic synthesis,and photocatalytic carbon CO₂ conversion.We developed a variety ofβ-ketoenamine connected COFs for photocatalytic CO ₂ reduction,photocatalytic BPA degradation and Cr（Ⅵ）reduction in this paper.The details are described as follows:（1）We synthesized two types of covalent organic frameworks ofβ-ketoenamine groups Tp Pa-SO₃H and Tp Pa.The photocatalytic properties of the two materials were evaluated through the experiment of photocatalytic reduction of CO ₂.The results show that the yields of Tp Pa-SO₃H and Tp Pa reducing CO ₂ to CO within 4 hours are416.61μmol g^-1and 380.68μmol g^-1,respectively.In addition,the Tp Pa-SO₃H photocatalyst showed chemical stabilities and reusability.The amount of CO produced is 415.23 and 409.15μmol g^-1 after two cycles of testing under visible light irradiation.XRD shows that the spectra of Tp Pa-SO₃H are basically consistent before and after the cycle.Therefore,the Tp Pa-SO₃H photocatalyst showed good stability and repeatability.To sum up,Tp Pa-SO₃H has good photocatalytic activity.This is because of the introduction of-SO₃H,which makes Tp Pa-SO₃H have a narrower bandgap,thus enhancing the visible light response range and greatly promoting the separation ability of pho to-generated electrons.（2）We synthesized two tr iazine covalent organic frameworks TpTt and Tri CF with different structure-activity relationships.The photocatalytic performance of the two materials was evaluated by degrading BPA and reducing Cr（Ⅵ）.The obtained results show that under simulated solar light irradiation,the TpTt exhibited outstanding catalytic efficiency compared with Tri CF.The photocatalytic degradation rate of 20 mg/L BPA by 10 mg TpTt reached more than 95%within 120 min.The photocatalytic reduction of Cr（Ⅵ）by 5mg TpTt reached 90%within 22 min.In addition,the TpTt photocatalyst shows good stability and reusability,and it can still keep high activity after four cycles of testing under visible light.It shows that the spectra of TpTt before and after the XRD cycle are basically the same.Therefore,the photocatalytic activity of TpTt is much higher than Tri CF,which is due to theβ-ketoenamine and triazine structure of TpTt.