Metal–Organic Nanosheets (MONs): Exfoliation by Mechanical Grinding and Iodine Capture

Abstract

AbstractAn electron‐rich π‐conjugated organic linker H4BPDP (BPDP = biphenyl dipyrrole tetracarboxylic acid) is designed and subjected to metal‐assisted self‐assembly to afford a layered metal–organic framework (MOF), i.e., Cd‐BPDP. Single crystal X‐ray structure determination and analysis show that two corrugated layers of the MOF are intertwined to yield thick strands of porous 2D metal–organic nanosheets (MONs). It is shown that the latter can be delaminated by ultrasonication‐induced liquid‐phase exfoliation and mechanical grinding techniques, as evidenced by Tyndall light scattering and comprehensive microscopy investigations that include field emission scanning electron microscopy (FESEM), atomic force microscopy, and high‐resolution transmission electron microscopy. The MONs accessed by grinding permit notable capture of iodine when compared to the bulk layered MOF, i.e., Cd‐BPDP; the extent of iodine capture can be correlated with the magnitude exfoliation, which is essentially determined by the duration of grinding. The observed notable iodine capture is attributed to i) a large increase in surface area with exfoliation, ii) ability of the e‐rich π‐conjugated organic linker to form a charge‐transfer complex with iodine, and iii) the presence of free and uncoordinated carboxylic acids of the linker that reinforce binding of iodine through charge transfer. Thus, a notable capture of iodine by 2D MONs generated by mechanical exfoliation of a layered MOF constructed from an e‐rich π‐extended organic linker is compellingly demonstrated.