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

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 7.0 wt%, and the corresponding photodegradation rate for RhB was 0.0624 min−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.