Recently, photoelectro-Fenton (PEF) technology has been widely employed to treat contaminants of emerging concerns (CECs) owing to their high efficiency and wide range of applications. The development of stable catalysts that offer a wide working pH range, high metal cycling ability, and reduced iron sludge formation is one of the main goals that have yet to be tackled. Layered double hydroxides (LDH) with an improved specific surface area and recyclability have aroused much attention as catalysts in pollutant degradation. Traditional synthesis techniques of LDHs are complicated and have poor control of the morphology. Therefore, a template-based synthesis where the growth of the LDH layers is centered around uniformly dispersed metal nodes, generating evenly expanded two-dimensional layers has gained recent importance. Herein a template-based conversion of MIL-101(Fe) to generate NiFe LDH as an efficient catalyst for PEF degradation is reported. A straightforward hydrothermal synthesis is adapted where the morphology of the NiFe LDH was controlled by adjusting the hydrolysis temperature and time, thereby limiting the degree of template etching. The XRD pattern showed an increase in crystallinity with increased hydrolysis temperature, and peaks at 11.6°, 23.2°, 34.5°, and 59.9° corresponding to (003), (006), (012), and (110) of NiFe LDH were observed. The major diffraction peak of MIL-101(Fe) at 8.9° was also observed at lower hydrolysis time suggesting the formation of core-shell MOF/LDH composites. The chemical and physical properties of the samples are probed using UV-vis, FTIR, Raman, SEM, XPS, and TEM. The catalytic properties and the organic pollutant degradation efficiency will be evaluated via PEF reactions. Compared to conventionally synthesized LDHs, these template-derived samples offer more active sites, prevent stacking and aggregation, and offer higher mass transfer rates. LDH derived at different hydrolysis conditions, namely core-shell and hollow structures will be compared based on their activity towards the CECs degradation. The CEC degradation pathway, the interaction of H2O2 with the active Fe sites, and the different radicals generated during the PEF reaction will be further assessed by DFT studies, and as such this study will provide new practical insights into the development of MOF-derived LDH catalysts for Fenton-like systems.

MIL-101(Fe) template-directed growth of NiFe LDH as an efficient catalyst for the heterogenous photoelectro-Fenton process

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