One Atom Can Make All the Difference: Gas-Induced Phase Transformations in Bisimidazole-Linked Diamondoid Coordination Networks

Abstract

Coordination networks (CNs) that undergo gas-induced transformation from closed (nonporous) to open (porous) structures are of potential utility in gas storage applications, but their development is hindered by limited control over their switching mechanisms and pressures. In this work, we report two CNs, [Co(bimpy)(bdc)] n (X-dia-4-Co) and [Co(bimbz)(bdc)] n (X-dia-5-Co) (H 2 bdc = 1,4-benzendicarboxylic acid; bimpy = 2,5-bis(1H-imidazole-1-yl)pyridine; bimbz = 1,4-bis(1H-imidazole-1-yl)benzene), that both undergo transformation from closed to isostructural open phases involving at least a 27% increase in cell volume. Although X-dia-4-Co and X-dia-5-Co only differ from one another by one atom in their Ndonor linkers (bimpy = pyridine, and bimbz = benzene), this results in different pore chemistry and switching mechanisms. Specifically, X-dia-4-Co exhibited a gradual phase transformation with a steady increase in the uptake when exposed to CO 2 , whereas X-dia-5-Co exhibited a sharp step (type F-IV isotherm) at P/P 0 0.008 or P 3 bar (195 or 298 K, respectively). Single-crystal X-ray diffraction, in situ powder XRD, in situ IR, and modeling (density functional theory calculations, and canonical Monte Carlo simulations) studies provide insights into the nature of the switching mechanisms and enable attribution of pronounced differences in sorption properties to the changed pore chemistry.

Shape‐Memory Effect Enabled by Ligand Substitution and CO2 Affinity in a Flexible SIFSIX Coordination Network

“…Whereas grafting of functional groups onto linkers affects flexibility and sorption profiles, single atom substitution has little impact upon host structure yet can still profoundly impact flexibility and sorption profiles. Specifically, the “linker engineering” detailed herein, was found to modulate switching between flexible and ‘rigid‘ phases, rather than gate‐opening pressure and/or isotherm shape modification as seen previously for the same ligand pair [19b] . From a property perspective, the “memorized” α′ (open) phase induced by CO 2 sorption exhibited excellent CO 2 /N 2 (15/85) separation performance at 298 K and 1 bar, conditions that would be infeasible for the activated β (non‐porous) form.…”

High-Capacity Iodine Adsorption and Nonporous to Porous Structural Transformation in an Originally Nonporous Coordination Polymer

“…21,22 There are also a few reports on the guest adsorption by nonporous crystals in the field of CPs. 19,20,[26][27][28][29][30] Studies on flexible metal-organic frameworks (MOFs) showed that the pore size would be enlarged when absorbing guest molecules. 31,32 They usually transform from narrow pores to larger pores, with only a few extreme examples transferring from nonporous to porous stages.…”

Engineering Colossal Anisotropic Thermal Expansion into Organic Materials through Dimensionality Control

“…Modulating the solid-state property of thermal expansion (TE), which describes the response of a material to a change in temperature, − is of utmost importance for fabricating materials with extraordinary performance. − Depending on the intended application, specific TE behaviors are often required. For example, materials that exhibit large TE behavior are useful for thermomechanical actuators and sensors. − On the other hand, materials that undergo smaller changes in response to temperature alterations are useful in ceramics and aerospace applications. , In the field of semiconductor and composite materials, the TE behavior of all the components needs to be adequately matched to avoid device failure when temperature changes occur. − One significant challenge that materials scientists face lies in controlling a material’s structure, and this control is critical because structure directly influences properties. − Control over solid-state structure is often accomplished by directing atomic or molecular self-assembly and packing in all dimensions. − However, depending on the atomic or molecular building blocks, some dimensions may not be easily self-assembled with the assistance of strong interactions.…”