Influence of ligands in Fe-MOFs on deriving iron oxide (α-Fe2O3) nanostructures for enhanced photocatalytic degradation and water splitting reactions

This study presents the synthesis of iron oxide (IO) nanostructures using iron metal-organic framework (Fe-MOF) as a template-precursor. It provides insights into how the ligands such as terephthalic acid (TA-MOF) and 2-aminoterephthalic acid (ATA-MOF) in Fe-MOFs influence the structural, morphological, and physiochemical properties of resulting IO (TA-IO and ATA-IO) systems compared to the conventionally obtained iron oxide (C-IO). The XRD results confirmed the formation of Fe-MOFs and hematite (α-Fe2O3) phase of the derived iron oxide systems with improved crystallinity and decreased crystallite size. The chemical environment analysis by XPS revealed the presence of multivalent Fe ions and O-vacancies, indicated the existence of defects-mediated electron-hopping between Fe2+ and Fe3+ states in the MOF-derived IO systems compared to C-IO. The microscopic images showed the MOF-templated anisotropic rod-like morphologies for the ATA-MOF-derived IO, while it is a bulky morphology for TA-IO and C-IO. An inherited broad range of visible light absorption with narrow band gap energy (∼2.16–2.18 eV) along with decreased recombination resistance is observed for the derived IO systems, influenced by the ligands. The solar-driven photocatalytic efficiency of ATA-IO in degrading Congo red (CR), rhodamine B (RhB) dye, and bisphenol A (BPA) is around 98, 100, and 91 %, while it is around 83, 85, and 71 % for conventional-IO. Similarly, an impressive H2 production at a rate of 987.2 µmol/g/h is observed for the ATA-IO, which is around 1.5 times higher than the conventional IO (671.1 µmol/g/h). The cyclic degradation of CR dye and H2 production by ATA-IO is consistent for several cycles compared to the C-IO, indicated the excellent stability of the inherited robust active sites in the ATA-IO system. The findings of this study reveal that MOFs can serve as a template-precursor for inheriting both morphology and physiochemical properties into metal oxides suitable for materials applications. [Display omitted]