Facile synthesis a novel core–shell amino functionalized MIL-125(Ti) micro-photocatalyst for enhanced degradation of tetracycline hydrochloride under visible light

Abstract

Abstract Titanium-organic frameworks have been widely appreciated for its photoelectric catalytic properties. However, the weak utilization of visible light by titanium-organic frameworks limits the application. In this paper, a novel core–shell micro-photocatalyst (TPE-2NH2@MIL-125(Ti)) was successfully prepared by the simple one-step alcohol-thermal modification of the nitrogenous organic ligand ((E)-4′,4′’’-(1,2-diphenylethene-1,2-diyl)bis([1,1′-biphenyl]-4-amine), TPE-2NH2) on the surface of MIL-125(Ti) for tetracycline hydrochloride (TC) degradation under visible light. The as-obtained samples were characterized by field emission scanning electron microscopy, transmission electron microscopy, powder X-ray diffractometer, infrared spectra, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, UV–visible diffuse reflectance spectra, photoluminescence spectra, zeta potential, high performance liquid chromatography mass spectrometry and electrochemical measurements. The results showed that the hybrid materials had lower band-gap energy and higher electronegativity than pure MIL-125(Ti), as well as rapid and strong response to visible light. Under the irradiation of visible light, the final removal efficiency of TC by TPE-2NH2@MIL-125(Ti) reached about 90% with little interference from the environment pH and even better removal effect was obtained in real water samples. Mechanism studies showed that •O2− and h+ were the main active species in the catalytic process. The enhanced photocatalytic performance is mainly attributed to the rapid photoelectron transfer, Ti4+-Ti3+ interlayer electron transfer, and the synergistic effect between TPE-2NH2 and MIL-125(Ti). As far as we know, this current work first provides a convenient method to improve the photocatalytic performance of titanium metal–organic frameworks (MOFs) by surface coating with amino conjugated organic molecule, and provides a new idea for the degradation of organic matter by hybrid MOFs materials in wastewater.