Chemoselectivity Inversion of Responsive Metal-Organic Frameworks by Particle Size Tuning in the Micrometer Regime

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Flexible metal-organic frameworks (MOFs) exhibit unique gated adsorption properties.
• Designing MOFs for selective guest molecule adsorption is challenging.
• Existing strategies focus on chemical modification, lacking a universal approach.

Purpose of the Study:

• To demonstrate the tunability and reversal of gate opening selectivity in MOFs.
• To establish particle size engineering as a strategy for controlling MOF adsorption behavior.
• To investigate the effect of crystal size on the selective adsorption of guest molecules in DUT-8(Zn).

Main Methods:

• Synthesis and characterization of DUT-8(Zn) with varying particle sizes.
• Adsorption/desorption studies using dichloromethane and alcohols as guest molecules.
• Analysis of phase transitions (open to closed pore phases) in response to guest molecules.

Main Results:

• DUT-8(Zn) microcrystals exhibit selective gate opening for dichloromethane over alcohols.
• Downsizing DUT-8(Zn) to micron size unexpectedly reverses this selectivity.
• Smaller DUT-8(Zn) crystals preferentially adsorb alcohols while suppressing dichloromethane uptake.

Conclusions:

• Particle size engineering is a viable strategy to control and reverse the selective gated adsorption of flexible MOFs.
• This finding offers new design principles for MOFs in selective adsorption and sensing applications.
• The study highlights the critical role of crystal size in modulating MOF properties.