Boosting Photocatalytic Performance in Mixed-Valence MIL-53(Fe) by Changing Fe^II/Fe^III Ratio

Abstract

One of vital issues that inhibit photoactivity of metal−organic frameworks is the poor electrical conductivity. In this work, one-dimensional mixed-valence iron chains are used to improve this poor situation in . A series of mixed-valence MIL-53(Fe) photocatalysts were obtained through heating at different temperatures in vacuum. The effect of Fe II coordinatively unsaturated metal sites (CUS) and one-dimensional mixed-valence iron chains on their photocatalytic property was discussed. The experimental results indicated that mixed-valence MIL-53(Fe) with a reference Fe II /Fe III ratio of 0.2725 displayed the best photocatalytic performance, which showed 96.28 and 95.01% removal efficiencies of RhB and TC-H in 100 min, respectively. Moreover, MIL-53(Fe) heated in vacuum displayed better catalytic activity than MIL-53(Fe) heated in air for RhB and TC-H degradation. Based on the analysis of various characterizations, the reinforced catalytic activity can be attributed to the charge mobilities in mixedvalence Fe II /Fe III chains. It is worth mentioning that the method is also applicable to MIL-88(Fe) and MIL-101(Fe). Additionally, mixed-valence MIL-53(Fe) can also perform the catalysis reaction in the nighttime by activating persulfate (PS) to produce free radicals. Interestingly, it was found that the Fe II CUS lost in activating PS can be supplemented by self-reduction of photogenerated electrons during illumination in the daytime, so as to achieve a more stable cycle. This work demonstrated that the photoactivity of MIL-53(Fe) can be improved by adjusting the ratio of Fe II /Fe III and the feasibility of using as an all-dayactive catalyst.

Photocatalytic Activities of FeNbO4/NH2-MIL-125(Ti) Composites toward the Cycloaddition of CO2 to Propylene Oxide

“…It was proven that the NH 2 -MIL-125(Ti) photoreaction proceeds via the (LMCT) ligand to metal charge transfer [16]. Upon light irradiation, generated electrons from the linker are transformed to Ti 4+ to facilitate its reduction to Ti 3+ [37,38] while methanol acts as an electron donor (Figure 7a). Evidently, there are two competing processes involved; the first indicates much of the CO 2 molecules were adsorbed into the NH 2 -MIL-125(Ti), the second involves the formation of a carbon dioxide radical anion which facilitates the cycloaddition to epoxide.…”

Morphology evolution of acetic acid-modulated MIL-53(Fe) for efficient selective oxidation of H2S

“…For the O 1s spectra, the two deconvoluted peaks at 530.2 eV and 531.7 eV can be ascribed to Fe-O and C=O (Fig. 5C) [45,46]. It is found that with the increase of HAc content, the Fe-O peak also shows an increasing trend, reflecting that the introduction of HAc facilitates the formation of Fe-O sites.…”

A Review of MOFs and Their Composites‐Based Photocatalysts: Synthesis and Applications

“…Among them, Fe 3+ ion is considered as an excellent candidate due to its high thermal stability and good structure stability. [ 160,161 ] For instance, the coordinatively unsaturated Fe 3+ ions were injected into PCN‐224 (Fe/PCN‐224) through a simple method by Shi and co‐workers to boost the photocatalytic performance of the PCN‐224. [ 162 ] In this report, the PCN‐224 was first prepared via a hydrothermal reaction route; the Fe 3+ ions were then introduced into the PCN‐224 unit by a one‐step precipitation method under 120 °C for 12 h; finally, the Fe/PCN‐224 composites photocatalysts with a uniform polyhedral morphology ( Figure a) were successfully fabricated.…”