Designed synthesis of perylene diimide-based supramolecular heterojunction with g-C₃N₄@MIL-125(Ti): insight into photocatalytic performance and mechanism

A new supramolecular semiconductor perylene diimide (PDI)-functionalized g-C₃N₄@MIL-125(Ti) (is nominated as PC@MIL-125(Ti)) was prepared through in situ growth of MIL-125(Ti) on PDI-functionalized g-C₃N₄ (PC) sheets. This heterojunction was used for photodegradation of methyl orange (MO) pollutants under visible light illumination. This process was sensitive to the pH of solution, dosage of PC and the presence of the various scavengers. The 30PC@MIL-125(Ti) as optimum photocatalyst indicated synergistic effects on photodegradation of MO, where the maximum photocatalytic efficiency was obtained 100% under 90 min irradiation that was higher than pure PC and MIL-125(Ti). Herein, the PDI component acts as a powerful light harvester and improves absorption of visible light where PC@MIL-125(Ti) has a lower bandgap than g-C₃N₄@MIL-125(Ti). Moreover, proper contact between PDI and g-C₃N₄ sheets constructs the highway for easy and fast electron transfer that verified by photoluminescence analysis. The sum of these factors resulted in the superior photocatalytic ability of this heterojunction, where the TOC analysis confirmed 91% mineralization for MO. Besides, according to the results of LC-MASS analysis, the azo cleavage and dealkylation were main photodegradation pathways. By considering superior photocatalytic performance of this heterojunction, this work can be a guideline for the development of PDI-based supramolecular organic–inorganic photocatalyst.