Tailoring structural and defect properties of hydrothermally-synthesized MIL-100(Fe) via mineralizers for improved xylenol orange adsorption

A simple mineralizer regulation strategy is developed to tune the structure of hydrothermal MIL-100(Fe). • NaHCO 3 enhances the surface area of MIL-100 (Fe), affording superior XO adsorption performance. • Synergistic pore adsorption, hydrogen bonding, Fe 3+ coordination and π-π stacking enable efficient XO removal. Metal-organic frameworks (MOFs) are promising crystalline porous solids, whose functional properties are highly dependent on their crystallinity, defect states and pore characteristics. In this work, hydrothermal synthesis was employed to prepare MIL-100(Fe) materials modulated by three different mineralizers: sodium carbonate, acetic acid, and sodium bicarbonate; mineralizer-free pristine MIL-100(Fe) was used as the reference sample. The addition of mineralizers effectively modulates the crystal structure and porosity of MIL-100(Fe). All mineralizer-modified samples exhibit larger specific surface area compared with the pristine material. Among them, NaHCO 3 -regulated MIL-100(Fe) achieves the best adsorption performance toward xylenol orange (XO), which originates from its optimized porous structure. Adsorption experimental data fit well with the pseudo-second-order kinetic model and Langmuir isotherm model. The maximum monolayer adsorption capacity calculated by the Langmuir model reaches 155.28 mg/g, which is competitive with many reported adsorbents. Synergistic adsorption mechanisms, including pore-filling effect, hydrogen bonding, Fe 3+ complexation and π-π stacking interactions, have been elucidated. This work presents a facile mineralizer-mediated strategy for tuning the solid-state structural features of MIL-100(Fe), offering experimental insights for the structure-performance optimization of Fe-based MOF solids. Download: Download high-res image (357KB) Download: Download full-size image