Trapping guests within a nanoporous metal-organic framework through pressure-induced amorphization

Area of Science:

• Materials Science
• Chemical Engineering
• Nuclear Chemistry

Background:

• Nanoporous metal-organic frameworks (MOFs) are investigated for molecular capture and storage.
• The release of guest species from MOFs can be problematic, limiting their applications.
• Amorphization of MOF structures under pressure has been observed to affect guest species release.

Purpose of the Study:

• To investigate the effect of pressure-induced amorphization on the retention of molecular iodine (I2) within the ZIF-8 MOF.
• To explore the potential of this amorphization strategy for hazardous radiological byproduct management.

Main Methods:

• Thermogravimetric analysis (TGA) was used to study the sorption and release of I2.
• Pair distribution function (PDF) analysis was employed to examine the structural changes in ZIF-8 upon amorphization.
• Sorption and amorphization experiments were conducted on both vacant and I2-loaded ZIF-8.

Main Results:

• Amorphization of ZIF-8 after I2 sorption was found to inhibit the release of I2.
• The distorted pore apertures resulting from amorphization kinetically trap I2, significantly improving retention.
• PDF analysis confirmed that the local structure of trapped I2 remained unchanged, and amorphization occurred under similar pressure conditions for both vacant and guest-loaded frameworks.
• The pressure required for this enhanced retention is lower than that needed for traditional sorbents like zeolites.

Conclusions:

• Pressure-induced amorphization of ZIF-8 is an effective strategy to enhance the retention of molecular iodine.
• This approach offers a promising method for the capture, interim storage, and controlled release of hazardous materials like I2.
• The findings suggest new possibilities for MOFs in nuclear energy applications and beyond.