Cucurbit[7]uril encapsulated dye-sensitized enhanced solar photocatalysis using positively charged sheet-like anatase TiO2 mesocrystals

• Published in: Applied surface science Vol. 488; pp. 911 - 920
• Main Authors: Mohanan, Deepu, Sumina, N.B., Thomas, Reny Thankam, Mohamed, A.P., Hareesh, U.S., Ray, Alok K., Pillai, Saju
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-09-2019
• Subjects: CB7; Dye-sensitized charge transfer; Host-guest inclusion complex; Mesocrystals; Solar photocatalysis; Visible active TiO2; Wastewater treatment; Solar photocatalysis; Dye-sensitized charge transfer; Mesocrystals; Host-guest inclusion complex; CB7; Wastewater treatment; Visible active TiO2
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2019.05.323

Recent progress in the field of advanced oxidation process (AOP) has triggered the use of surface engineered visible light active TiO2 as a competent photocatalyst material in solar photocatalysis. Herein, we adopted host-guest inclusion complexation for the site-directed immobilization of a model cationic dye, Rhodamine B (RhB) on to the surface of oxygen-rich positively charged TiO2, resulting in rapid mineralization of the dye pollutant under solar irradiation. Relatively recent macrocyclic host, cucurbit[7]uril (CB7) is used as the host for the formation of inclusion complex with RhB. In this study, solar photocatalysis of dye encapsulated system results in 97% mineralization of dye molecules within 10 min with an excellent kinetic rate of 351 × 10−3 min−1. Here, the formation of CB7-RhB inclusion complex enables direct anchoring of encapsulated dye molecules through carboxylic (-COOH) groups of RhB, which in turn facilitate heterogeneous electron transfer resulting in instantaneous and direct cleavage of the chromophore. The binding of CB7 encapsulated RhB to microwave-assisted sonochemically synthesized TiO2 (MST) surface via monodentate ester-like linkage was established by XPS and FT-IR analysis. Gas chromatography (GC) and high-resolution mass spectrometry (HR-MS) substantiate the complete mineralization of RhB and the intactness of CB7 molecular structure after photodegradation, confirming the reusability of CB7/MST as an efficient and economically viable photocatalytic system. Encapsulation of pollutant dye to CB7 host proves to be an excellent approach to facilitate the photoelectron transfer to the photocatalyst and faster mineralization of dye molecules under solar irradiation. Thus, our approach would be a feasible solution for environment-friendly remediation of dye pollutants.
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•Host-guest inclusion complex helps in the efficient immobilization of RhB dye pollutant on TiO2 mesocrystals (MST).•Synergistic effect of CB7 encapsulated RhB and visible light active MST photocatalyst in the rapid mineralization of dye pollutant has been studied.•A mechanistic investigation on the heterogeneous electron transfer has been carried out using XPS and FTIR.•Complete mineralization of RhB and the intactness of CB7 was confirmed from GC and HR-MS analysis.•The reusability studies of CB7/MST dispersion were carried out.