Particle size effects on vapour uptake and release dynamics in metal-organic frameworks

Area of Science:

• Materials Science
• Chemical Engineering
• Adsorption Science

Background:

• Metal-organic frameworks (MOFs) are porous materials with tunable properties.
• Particle size significantly influences the performance of MOFs in adsorption and release applications.
• Understanding guest molecule diffusion in MOFs is crucial for optimizing their use.

Purpose of the Study:

• To investigate the effect of particle size on the adsorption and release dynamics of volatile semiochemicals in MIL-68(In) and ZIF-8.
• To elucidate the relationship between MOF structure, particle size, and guest diffusion mechanisms.
• To provide insights into designing MOFs for controlled release applications.

Main Methods:

• Synthesis and characterization of MIL-68(In) and ZIF-8 with varying particle sizes.
• Adsorption experiments to quantify the uptake of volatile semiochemical guests.
• Release kinetic studies to measure the rate of guest molecule desorption.
• Analysis of diffusion pathways and barriers within the MOF structures.

Main Results:

• Reduced particle size of MIL-68(In) and ZIF-8 increased the adsorption capacity for volatile semiochemical guests.
• Isobutyl acetate release rate increased with particle size for MIL-68(In) but decreased for ZIF-8.
• Diffusion through channels in ZIF-8 was faster than diffusion between discrete pores in MIL-68(In).

Conclusions:

• Particle size is a critical parameter affecting both adsorption and release of guests in MOFs.
• The distinct diffusion mechanisms in MIL-68(In) (pore-based) and ZIF-8 (channel-based) lead to opposing size-dependent release trends.
• These findings highlight the importance of considering MOF structural features and particle size for targeted applications in controlled release systems.