Iron-Based nanoporous Metal-Organic frameworks with Side-Chain amino substituents for Efficiency-Regulated oxygen evolution reaction

Abstract

Nanoporous iron-based MOFs, possessing notable attributes such as adjustable structure, considerable porosity, and large surface area, exhibit considerable promise for various applications in the field of photocatalysis. However, the effect of the ligand substitution ratio on the photocatalytic reaction process is currently unknown. In the current investigation, a series of iron-based MOFs MIL-101(Fe)-X with various ratios of amino substituents (X = H: NH2 = 1:0, 1:0.5, 1:1, 1:2, 1:4, 0:1) were synthesized using the solvothermal method. The morphology and structure were characterized using SEM, TEM, XRD, XPS, BET, FT-IR, etc. Their efficacy as water oxidation catalysts under AM1.5G (solar light) irradiation was investigated. The findings of the study indicated that MIL-101(Fe) with an X value of 1:2 exhibited the highest surface area of 380.4 m2/g. This resulted in the exposure of a greater number of active sites, leading to enhanced charge separation efficiency and exceptional oxygen evolution activity when illuminated by simulated sunlight. The oxygen evolution rate under solar light was measured to be 11.7 mmol·h−1·g−1. This research confirmed the effect of substituent variation on the oxygen evolution rate by modulating the substitution ratio of side-chain ligands on MOFs, thereby altering their microstructure and charge distribution. The incorporation of a suitable quantity of amino groups, that act as strong electron-donating groups, facilitated the effective separation of electron-hole pairs generated during the photocatalytic process. However, an excessive introduction of amino groups can result in a reduction in both pore structure and surface area, thereby impeding the efficiency of the photocatalytic oxygen evolution reaction.