Synthesis and applications of novel graphitic carbon nitride/metal-organic frameworks mesoporous photocatalyst for dyes removal

Abstract

Metal-organic frameworks (MOFs) have been attracted considerable attention for their applications in gas storage/separation, adsorption as well as catalysis. In this study, a facile solvothermal method was employed to prepare MOFs and graphitic carbon nitride (g-C3N4) hybrids, and a g-C3N4/Ti-benzenedicarboxylate (MIL-125(Ti)) heterostructures photocatalyst was successfully synthesized. The as-obtained materials were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption-desorption isotherm, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflection spectroscopy (UV-vis DRS), and photoluminescence (PL) spectroscopy. It is indicated that the hybrids have large surface area, mesoporous structure, thermal stability, and enhanced visible-light absorption. Compared with pure MIL-125(Ti) and g-C3N4, the composites exhibited more efficient photocatalytic performance for Rhodamine B degradation from aqueous solution under visible-light irradiation. The optimal g-C3N4 content in g-C3N4/MIL-125(Ti) composite was determined to be 7.0wt%, and the corresponding photodegradation rate for RhB was 0.0624min-1, about 2.1 and 24 times higher than that of pure g-C3N4 and MIL-125(Ti), respectively. The indirect dye photosensitization, the Ti3+-Ti4+ intervalence electron transfer, and the synergistic effect between MIL-125(Ti) and g-C3N4 were the three reasons for improved photo-degradation performance. Therefore, it is reasonable to believe that metal-free semiconductor/MOFs photocatalysts have great potentiality in environmental remediation.