Design and Synthesis of Porous Smart Materials
Primary author: Qiang Zhang
Co-author(s): Matthew Hurlock
Primary college/unit: Arts and Sciences
Zirconium Metal-Organic Frameworks (Zr-MOFs) have recently emerged as a distinct family of porous materials. Generally, Zr-MOFs are formed from Zr clusters made of six Zr atoms bonded together by oxygen atoms forming secondary building units (SBUs). Though many Zr-MOFs have been synthesized over the last decade none have shown a cluster coordination of more than 12 ligands. Coordination through only one oxygen atom of the carboxylic acid suggests that a coordination of up to 24 ligands could be achieved greatly increasing the number of structures Zr-MOFs can form. Current investigations have shown steps toward reaching this goal.
The new Zr-MOF WSU-5 (Washington State University-5) was synthesized through solvothermal methods from ZrCl4 and the tetracarboxylate linker H4ETTC. Utilizing post-synthetic modification, WSU-5 was transformed into WSU-6 and WSU-7 through the insertion of 1,4-benzenedicarboxylic acid (BDC) and 2,6-napthalenedicarboxylic acid (NDC), respectively. Crystallographic analysis show that WSU-5 is comprised of 8-connected Zr6-SBUs and the 4-connected ligands H4ETTC. Therefore, WSU-5 possesses the uncommon (4,8)-connected interpenetrated scu-c topology. The insertion of BDC into WSU-5 coordinated four BDC ligands into each SBU. This formed the (4,12)-connected WSU-6 with the new mjh topology. Interestingly, when NDC was inserted into WSU-5, six NDC ligands coordinated to the Zr6-SBUs. Two through bidentate coordination and four though monodentate coordination. The (4,14)-connected WSU-7 was generated, which exhibits a new topology, jkz. The Zr6-SBUs of WSU-7 is the first Zr-MOF to contain 14-connected Zr6-SBUs. The insertion alters the luminescent properties which can be used as sensors.