Evaluating Iodine Uptake in a Crystalline Sponge Using Dynamic X-ray Crystallography.

Area of Science:

• Materials Science
• Inorganic Chemistry
• Crystallography

Background:

• Crystalline sponge materials offer porous frameworks for guest molecule encapsulation.
• Understanding guest-host interactions is crucial for designing functional porous materials.
• Previous studies on related materials showed different iodine species formation.

Purpose of the Study:

• To investigate the uptake of gaseous iodine into a specific crystalline sponge material.
• To determine the kinetics, location, and chemical state of iodine within the material's pores.
• To compare the iodine uptake and speciation with related materials lacking guest molecules.

Main Methods:

• Dynamic X-ray diffraction was employed to monitor iodine uptake in real-time.
• Thermogravimetric analysis quantified the amount of iodine absorbed.
• Crystallographic analysis determined the precise location and interactions of iodine guests.

Main Results:

• An iodine uptake of 6.0 wt% (0.43 I2 per formula unit) was achieved within 90 minutes.
• Crystallography revealed iodine molecules interacting at three distinct sites within the pores.
• Coordinated I3- ions were identified as the primary iodine species formed within the crystalline sponge.

Conclusions:

• The crystalline sponge material [(ZnI2)3(tpt)2]·0.7triphenylene·0.3PhNO2·0.7C6H12 demonstrates efficient gaseous iodine uptake.
• The presence of triphenylene guests influences the formation of I3- ions, contrasting with I42- in guest-free analogues.
• Dynamic X-ray diffraction is a powerful tool for studying guest inclusion and host-guest chemistry in porous materials.