Surface Modifying Mil-125(Ti) by Devisable Poly(Amino) Conjugate Molecule to Significantly Enhance its Visible Light Photo-Degradation Properties

A novel core/shell nanocomposite was successfully synthesized through surface coating MIL-125(Ti) with a poly(amino) conjugate molecule (4′,4‴,4⁗′,4⁗‴-(ethene-1,1,2,2-tetrayl)tetrakis([1,1′-biphenyl]-4-amine)) by the facile one-step solvothermal method for improving the photocatalytic properties under visible light. The nanocomposite was detailed characterized through TEM, SEM, XRD, FT-IR, BET, EDS and XPS. Photoelectrochemical characterizations showed that the nanocomposites exhibited lower band gap as well as excellent migration and separation efficiency of photo-generated charges compared with the original MIL-125(Ti). The optimized nanocomposite (TNMT-2) exhibited an excellent photo-degradation effect for a representative organic contaminant tetracycline hydrochloride and the total tetracycline hydrochloride removal efficiency can reach 96.5 % under visible light illumination, and higher removal efficiency was received in practical water treatment. In addition, TNMT-2 nanocomposite showed great reusability, stability, and applicability. Furthermore, the photo-degradation mechanism and the photo-degradation pathways of tetracycline hydrochloride were investigated. The relationship between the photocatalytic properties of the nanocomposite and the structure of the organic molecular were explored, and electron-donating groups as well as large π–π conjugate structure were the two most important factors. This study indicates that by designing the molecular structures, the photocatalytic properties of Ti-based MOFs can be easily regulated and TNMT-2 nanocomposite is an effective visible light catalyst for organic pollutants with great applicable potential.