Cyclobenzil hydrazones with high iodine capture capacities in solutions and on interfaces

Porous molecular crystals (PMCs) are solution-processable materials with promising applications in thin films and devices. However, some PMCs are only virtually porous, as their pores collapse when desolvated. We demonstrate the productive use of virtual porosity when non-volatile I2 guest acts as the probe. We prepared a series of cyclotetrabenzil hydrazones with progressively larger cavities. Their measured surface areas of up to 131 m2 g−1 are negligible compared with the values predicted from crystal structures. Nevertheless, they effectively capture I2 from aqueous and organic media and at the organic-aqueous interface, with capture capacities scaling with virtual void volumes. The pyridine-functionalized system is a notable outlier, engaging up to 21 I2 molecules and showing capture capacity of 4.15 g g−1, unprecedented among non-polymeric materials. These findings could impact the management of radioactive I2 and help in ensuring the integrity of protective coatings of nuclear reactors and waste containment vessels.