Defect and Particle-Size Engineering as Mechanistic Drivers for Dye Uptake in a Zirconium Metal-Organic Framework

Area of Science:

• Materials Science
• Nanotechnology
• Environmental Chemistry

Background:

• Precise control over metal-organic frameworks (MOFs) particle size and defect density is crucial for adsorption applications.
• Acid modulation is a key strategy for tuning MOF structural properties and adsorbate-adsorbent interactions.

Purpose of the Study:

• To investigate the influence of defect density and particle size on dye adsorption mechanisms in UiO-66 MOFs.
• To explore the effect of varying acetic acid concentrations during synthesis on MOF properties and adsorption performance.

Main Methods:

• Synthesis of UiO-66 MOFs using different acetic acid concentrations (75, 150, 300 equiv).
• Characterization of MOF particle size, surface area, and defect levels.
• Adsorption studies using methyl orange, methylene blue, and curcumin as probe molecules.
• Kinetic and isotherm modeling to understand adsorption mechanisms.

Main Results:

• Increasing acid concentration led to larger particle sizes (190-450 nm) but decreased dye adsorption capacity.
• Surface area and defect levels showed a non-linear dependence on acid concentration.
• Adsorption kinetics varied by dye and MOF sample, with PSO model fitting MO and MB adsorption well.
• Methyl orange showed the highest uptake, while methylene blue had the lowest.

Conclusions:

• Acid-modulated defect and particle-size engineering offers a mechanistic approach to tune dye adsorption in MOFs.
• This provides a pathway for the rational design of adsorbents with tailored interaction profiles for dye removal.
• Reaction time did not significantly affect structural properties or adsorption performance.