Photocatalytic degradation of dyes using TpPa-COF-Cl₂ membrane

The degradation of organic pollutants using photocatalysis is a more environmentally friendly method because it uses solar energy. Covalent organic frameworks (COFs) are photocatalysts that are composed of covalent bonds of light elements and do not contain harmful metals. COFs have been studied in various fields, but their use in removing organic pollutants has not been fully investigated. In this study, the photocatalyst TpPa-COF-Cl₂ was made into a membrane and its activity against dyes was examined. TpPa-COF-Cl₂ slightly decolorized methyl orange.

-Synthesis of catalyst

①Mesitylene (4.5 mL), 1,4-dioxane (4.5 mL), acetic acid (3M, 1.5 mL), 1,3,5-triformylphloroglucinol (Tp), and 2,5-dichloro-p-phenylenediamine (Pa) (molar ratio Tp:Pa=1:1.5) were added, heated, and stirred to obtain TpPa-COF-Cl₂ powder.

②A mixture of 20 mg of TpPa-COF-Cl₂ powder, sodium alginate, and 1.7 mL of water was heated and stirred, spread on a glass plate, and immersed in a CaCl₂ solution (3 wt%) for 24 hours to synthesize 5 to 6 TpPa-COF-Cl₂ films.

-Dye degradation

One membrane was placed in 5 ppm methyl orange (MO) and left in the dark for 30 minutes to reach adsorption equilibrium, after which it was irradiated with a 450 nm LED lamp for 60 minutes and its absorbance was measured every 10 minutes.

-Result, Conclusion

SEM and TEM revealed that the powdered TpPa-COF-Cl₂ had a layered structure. In addition, an absorption edge at 600 nm was confirmed by DRS.

The TpPa-COF-Cl₂ membrane formed by the cross-linking reaction of alginic acid and calcium ions maintained its structure even after the photocatalytic reaction. The TpPa-COF-Cl₂ membrane decolorized approximately 5% of MO. Although the decolorization efficiency was inferior to that of the powder form, it was easier to remove the catalyst.