Melem Nanorectangular Prism-Modified {Mo₇₂Fe₃₀} Nanocapsule as a Visible-Light-Assisted Photocatalyst for Catalase-Like Activity

In this work, the as-prepared 2,5,8-triamino-tri-s-triazine (Melem), which possesses nanorectangular prism morphology, the desired surface area, and photoluminescence properties, was combined with the Keplerate {Mo72Fe30} nanocapsule to produce a new heterojunction-like photocatalyst (M/K nanohybrid). After full characterization of the as-prepared M/K nanohybrid, its photocatalytic activity toward hydrogen peroxide (H2O2) dismutation was assessed under visible-light irradiation. To study the significance of independent variables, a response surface methodology based on a central composite design was employed to determine the optimal conditions for decomposition of the H2O2 process. Efficient H2O2 decomposition occurred within 3 h using a small amount of photocatalyst at pH = 3 and room temperature under a reptile light, rendering a high turnover number of up to ∼53000. The visible-light-assisted photochemical property of the M/K nanohybrid was confirmed by both the action spectra and dark-light experiments. Kinetic studies using the M/K nanohybrid revealed a first-order kinetic with a rate constant (k1 = 3 × 10–4 s–1) 100-fold larger than that of the free cluster {Mo72Fe30} and an activation energy (64.14 kJ mol–1) half the amount obtained by the free cluster. A synergistic effect between the {Mo72Fe30} nanocapsule and the Melem nanorectangular prism through a type II heterojunction-like mechanism sounds reasonable for promoting the photocatalytic activity of the as-prepared M/K nanocomposite. A nonradical molecular mechanism evidenced by the kinetic results and scavenging experiments was postulated. The title hybrid exhibited prominent reusability in photocatalysis, but disintegration of the Keplerate by H2O2 raised some concerns regarding the nature of the true catalyst!