De novo synthesis of photocatalytic bifunctional MIL-125(Ti)/gC₃N₄/RGO through sequential self-assembly and solvothermal route

In this study we have synthesized a heterostructured metal organic framework (MOF) consisting of self-assembled porous carbon nitride (gC₃N₄) and, reduced graphene oxide (RGO) with MIL-125(Ti) (CN-GO-MIL) through a simple synthesis route. As-synthesized CN-GO-MIL was characterized to determine its morphological, surface, structural, and optical properties. The synthesis produced a porous nanomaterial with efficient visible light capture and electron transport. CN-GO-MIL proved 2.23 and 1.23 times as effective as bare MIL-125(Ti) for Rhodamine B (RhB) degradation and chromium (Cr) reduction, respectively. We propose a governing photocatalytic degradation and reduction mechanism in which superoxide plays a major role in the photocatalytic degradation, followed by O₂¹, OH·, and holes, and identify methanol as a suitable hole scavenger for reduction of Cr. Moreover, Cr reduction can be best achieved at pH 2 in the presence of methanol. Performance of material in terms of apparent quantum yield (AQY), figure of merit (FOM), and catalyst surface efficiency (S.E), suggests 5% CN-GO-MIL is an efficient photocatalyst for degradation of RhB. Comparison of the AQY with previously reported MOF-based composites shows that the as synthesized 5% CN-GO-MIL can be regarded as one of best performing photocatalyst under visible light irradiation for abatement of organic and inorganic pollution.