Synthesis of a (3,7)-Connected Metal–Organic Framework by Post-Synthetic Linker Reorganization for High Iodine Adsorption

Abstract

Introducing complexity into metal–organic frameworks (MOFs) with specific topologies is attractive for modulating the porosities and functions of these materials for targeted applications. In this work, we report the construction of a novel multicomponent MOF via post-synthetic linker reorganization. By incorporating the ditopic azobenzene-4,4′-dicarboxylic acid (H₂AzoBDC) linker into MOF-177 crystals, which consist of 6-connected (6-c) Zn₄O(CO₂)₆ secondary building units (SBUs) and tritopic 1,3,5-tris(4-carboxyphenyl)benzene (H₃BTB) linkers, through a post-synthesis process, we obtained a rare (3,7)-c multicomponent MOF, [Zn₄O(BTB)(AzoBDC)₂(Et₂NH₂)] (WUST-3) based on a 7-c Zn₄O cluster and both linkers. The significant changes in connectivity and topology of WUST-3 can be attributed to the reorganization of two geometrically distinct linkers with a large linker length ratio. Impressively, WUST-3 shows exceptionally high adsorption capacity for iodine (3.34 g g^–1) in cyclohexane due to its porous structure with ionic moieties in the pore and the electron-rich, π-conjugated walls of the channel, which form strong and multiple host–guest interactions with iodine.