Breathing Transition\nand Effective Iodine Adsorption\nin a Temperature-Responsive Zn-Based Flexible Metal–Organic\nFramework

A porous and flexible Zn-MOF was synthesized under solvothermal\nconditions by using the ligand 2,5-furandicarboxylic acid (2,5-FDA).\nThis flexible Zn-MOF demonstrates a temperature-triggered breathing\neffect. At low temperature (100 K), we obtained the high-symmetry\nMOF denoted as <b>SM-A</b> with a unit cell volume of 1958 Å<sup>3</sup>, characterized by triangular narrow pore (np) channels. Upon\nincreasing the temperature from 100 K to 298 K, the lower symmetry\nreferred to as <b>SM-B</b> was obtained, featuring rhombic large\npore (lp) channels, along with an expanded unit cell volume of 7823\nÅ<sup>3</sup>. This temperature-induced phase transition involves\n distortion of the channels and a change in the dimensionality of\nthe framework from 3D (<b>SM-A</b>) to 2D (<b>SM-B</b>). The flexible behavior and phase transition were thoroughly justified\nwith the help of single-crystal X-ray diffraction and differential\nscanning calorimetry. Additionally, BET analysis revealed a surface\narea of 85.504 m<sup>2</sup>/g, with mesopores of 3.05 nm. Leveraging\nthe large-pore channels, <b>SM-B</b> at room temperature was\nemployed as an adsorbent for the removal of hazardous iodine in both\nthe vapor and the solution phases. The discovery of such dynamic MOFs\nholds potential and may pave the way for novel strategies in advanced\napplications.