Extreme Flexibility in a Zeolitic Imidazolate Framework: Porous to Dense Phase Transition in Desolvated ZIF‐4

Abstract

Desolvated zeolitic imidazolate framework ZIF-4(Zn) undergoes ad iscontinuous porous to dense phase transition on cooling through 140 K, with a2 3% contraction in unit cell volume.T he structure of the non-porous,l ow temperature phase was determined from synchrotron X-ray powder diffraction data and its density was found to be slightly less than that of the densest ZIF phase,Z IF-zni. The mechanism of the phase transition involves ac ooperative rotation of imidazolate linkers resulting in isotropic framework contraction and pore space minimization. DFT calculations established the energy of the new structure relative to those of the room temperature phase and ZIF-zni, while DSC measurements indicate the entropic stabilization of the porous room temperature phase at temperatures above 140 K.

Significant Enhancement of C2H2/C2H4 Separation by a Photochromic Diarylethene Unit: A Temperature‐ and Light‐Responsive Separation Switch

“…Such asmart material can be constructed with some specific elements on MOFs that are responsive to external stimuli, and accordingly shows dynamical alteration in their physical properties. [16][17][18][19] In view of this,controlling CO 2 uptake in MOFs has been achieved by heat, or light, or am agnet. [20] However, until now no case of using external stimulus to modulate adsorption selectivity in MOFs has been reported.…”

A Stable Amine‐Functionalized Microporous Metal–Organic Framework for Thermodynamically and Kinetically Selective Gas Separations

“…This abnormal N 2 adsorption behavior reveals the flexibility of Co 2 (abim)(im) 3 framework. A similar phenomenon was also clearly observed and extensively studied on ZIF‐4, which has a similar structure to the Co 2 (abim)(im) 3 . As reported, ZIF‐4 undergoes a reversible transformation from a porous to dense phase on cooling through 140 K. We believe that Co 2 (abim)(im) 3 also undergoes a similar structure transition.…”

The ZIF system zinc(II) 4,5-dichoroimidazolate: theoretical and experimental investigations of the polymorphism and crystallization mechanisms

“…ZIF-7 [33,34,43]) or may not (e.g. ZIF-8 [30,31] and ZIF-4 [44]) occur with a change of symmetry. In contrast, a similar step is not seen in the low-pressure region in case of the cubic material, demonstrating that static orientational linker disorder can affect framework dynamics.…”