Face-Capped M4L4 Tetrahedral Metal-Organic Cage: Iodine Capture and Release, Ion Exchange, and Electrical Conductivity

An (ML4)-L-4 type metal-organic cage (MOC-19) has been synthesized from the one-pot reaction of tri(pyridinylmethylene)phenylbenzeneamine (TPBA) with hydrated Zn(ClO4)(2) under mild conditions and characterized by single-crystal X-Ray diffraction. Iodine capture studies show that the porous crystals of MOC-19 exhibit a versatile behavior to accumulate iodine species not only in vapor (for I-2) but also in solution (for I-2 and I-3(-)), and anion-exchange experiments indicate the capacity to extract IO3- anions from aqueous solution. Enrichment of iodine species from KI/I-2 aqueous solution proceeds facilely, revealing a pseudo-second-order kinetics of I-3(-) adsorption. Furthermore, the electrical conductivity of MOC-19 single crystals could be significantly altered by I-2 inclusion.