Unveiling the Mechanism of Water‐Triggered Diplex Transformation and Correlating the Changes in Structures and Separation Properties

Abstract

Recently, great attention has been devoted to the initial and final structures of single‐crystal to single‐crystal (SCSC) transformations and dissolution‐recrystallization structural transformations (DRSTs), whereas the isolation and characterization of crucial intermediates and the unequivocal mechanism of the dynamic conversion process receive comparatively little consideration. Herein, a CuII‐based porous coordination polymer (PCP), which possesses a Kagomé lattice, is solvothermally synthesized. Triggered by water, the 2D Kagomé lattice (PCP‐1) primarily undergoes a reversible SCSC transformation to a distorted Kagomé intermediate (PCP‐2), which is followed by a DRST process to form a 3D NbO framework (PCP‐3) in situ. To the best of our knowledge, this is the first demonstration of a mixed SCSC and DRST transformation process. Notably, the sequential transformations result in the formation of the intermediate and the final product, which could not be obtained by direct synthesis. Regarding the intermediate, we have characterized the transformation separately and propose a plausible mechanism. More interestingly, the adsorption isotherms of water, methanol, and ethanol for the activated materials are distinctly different from one another. PCP‐2′ can uptake all three vapors with different adsorption capacities; however, the 3D transformed material PCP‐3′ only significantly absorbs water, which is concomitant with an amorphous‐to‐crystalline transformation, leading to the selective extraction of water from alcohol.

Mechanisms of Solvent‐Mediated Structural Transformations for Dynamic Crystals of Supramolecular Coordination Systems

“…Zang et al have revealed that a hexagonal crystalline Cu II ‐based PCP‐1 (PCP=porous coordination polymer), with the 2D Kagomé lattice, undergoes a solvent‐mediated structural transformation to form a strip‐like PCP‐3 crystal with a 3D NbO framework . The whole process follows the core‐on‐shell mechanism.…”

“…Zang et al have revealed that ah exagonal crystalline Cu IIbased PCP-1 (PCP = porous coordination polymer), with the 2D KagomØ lattice,u ndergoes as olvent-mediated structural transformation to form as trip-like PCP-3 crystal with a3 DN bO framework. [14] The whole process follows the core-on-shell mechanism. Crystals of PCP-1 in water first lose their transparency,a nd then the edges of the hexagon will be dissolved, and finally the green strip-like crystalsP CP-3 are recrystallized in situ ( Figure 5).…”

Structural Transformation Pathways of Alkaline Earth Family Coordination Polymers Containing 3,3′,5,5′‐Biphenyl Tetracarboxylic Acid

“…Very few studies exemplify the step-by-step crystal growth process. [18,19] Due to large radii, high and various coordination numbersof alkaline earth metal ions, the relatedCPs are difficult to be predesigneda nd directional synthesized. Especially for Sr 2 + and Ba 2 + ,t hey have received much less attention compared to other transition metal ions.…”

[(18‐Crown‐6)K][Fe(1)Cl(1)4]0.5[Fe(2)Cl(2)4]0.5: A Multifunctional Molecular Switch of Dielectric, Conductivity and Magnetic Properties

“…Functional materials featuring abrupt change of their physical and/or chemical properties in response to temperature fluctuation, pressure variation, light, electric/magnetic field, and other external stimuli have attracted great attention in the fields of molecular motors, optoelectronic technology, digital processing, sensors, etc . Most recent studies have been reported to design such materials, and a large number of materials possessing single‐switchable electrical, optical, or magnetic properties have been studied. However, with the development of science and technology, a simple function material has not fully satisfied the needs of application.…”