Understanding the adsorption process in ZIF-8 using high pressure crystallography and computational modelling

Abstract

Some porous crystalline solids change their structure upon guest inclusion. Unlocking the potential of these solids for a wide variety of applications requires full characterisation of the response to adsorption and the underlying framework–guest interactions. Here, we introduce an approach to understanding gas uptake in porous metal-organic frameworks (MOFs) by loading liquefied gases at GPa pressures inside the Zn-based framework ZIF-8. An integrated experimental and computational study using high-pressure crystallography, grand canonical Monte Carlo (GCMC) and periodic DFT simulations has revealed six symmetry-independent adsorption sites within the framework and a transition to a high-pressure phase. The cryogenic high-pressure loading method offers a different approach to obtaining atomistic detail on guest molecules. The GCMC simulations provide information on interaction energies of the adsorption sites allowing to classify the sites by energy. DFT calculations reveal the energy barrier of the transition to the high-pressure phase. This combination of techniques provides a holistic approach to understanding both structural and energetic changes upon adsorption in MOFs.

Long‐Term Photostability in Terephthalate Metal–Organic Frameworks

“…ZIF‐8 is composed by Zn 2+ ions tetrahedrally coordinated by four imidazolate rings with unit formula Zn 6 (mIm) 12 (mIm=2‐methylimidazolate). The structure contains one central nanopore per unit cell, with 2500 Å 3 volume and 11.6 Å pore diameter . ZIF MOF series containing imidazole based linkers has been widely used in different fields due to their robust structure, resistance to thermal changes and chemical stability .…”

Probing the Mechanochemistry of Metal–Organic Frameworks with Low-Frequency Vibrational Spectroscopy

“…19 In recent years, a number of studies, both experimental and theoretical, have been performed to study the role of pressure, temperature, and the nature of the gas molecules on the adsorption capacity of ZIF-8, including the apparently counterintuitive case of an increased pore window size upon pressure. [20][21][22][23][24][25] More specifically, using both in situ powder X-ray diffraction and molecular simulation, it has been shown that a "gate-opening" or "swing-effect" adsorption-induced structural change occurs in ZIF-8 at much lower pressures, where -similar to the 1.47 GPa phase described above -the imidazolate linkers rotate so as to increase the size of the accessible pore window. 21,26,27 These classes of motions, i.e.…”

Highly Ordered 3D Silicon Micro‐Mesh Structures Integrated with Nanowire Arrays: A Multifunctional Platform for Photodegradation, Photocurrent Generation, and Materials Conversion

“…The other converted material is ZIF‐8, which is a typical metal‐organic framework (MOF) with a porous 3D zeolite crystal structure. ZIF‐8 has been studied extensively and shows a great potential in catalysis, gas adsorption, and optics ,. Herein, solvothermal reaction was employed to convert the ZnO NWs into ZIF‐8 structures on the 3D Si substrate.…”