A Computational Study of Isopropyl Alcohol Adsorption and Diffusion in UiO-66 Metal–Organic Framework: The Role of Missing Linker Defect

Abstract

Defect engineering leads to an effective manipulation of the physical and chemical properties of metal–organic frameworks (MOFs). Taking the common missing linker defect as an example, the defective MOF generally possesses larger pores and a greater surface area/volume ratio, both of which favor an increased amount of adsorption. When it comes to the self-diffusion of adsorbates in MOFs, however, the missing linker is a double-edged sword: the unsaturated metal sites, due to missing linkers, could interact more strongly with adsorbates and result in a slower self-diffusion. Therefore, it is of fundamental importance to evaluate the two competing factors and reveal which one is dominating, a faster self-diffusion due to larger volume or a slower self-diffusion owing to strong interactions at unsaturated sites. In this work, via Monte Carlo and molecular dynamics simulations, we investigate the behavior of isopropyl alcohol (IPA) in the Zr-based UiO-66 MOFs, with a specific focus on the missing linker effects. The results reveal that unsaturated Zr sites bind strongly with IPA molecules, which in return would significantly reduce the self-diffusion coefficient of IPA. Besides this, for the same level of missing linkers, the location of defective sites also makes a difference. We expect such a theoretical study will provide an in-depth understanding of self-diffusion under confinement, inspire better defect engineering strategics, and promote MOF based materials toward challenging real-life applications.

Trace to the Source: Self‐Tuning of MOF Photocatalysts

“…[44] MOF-based OMS chemistry started with HKUST-1 (Hong Kong University of Science and Technology, BASF's Basolite C300 commodity). [205] A large body of research evidence suggests that OMS is a critical step in activating MOFs properties such as catalysis, [206][207][208][209][210] separation, [211][212][213][214] adsorption, [215][216][217][218][219] and sensing. [220,221] In this subsection, we will discuss how OMS-MOFs are a driver of photocatalytic activity.…”

Probing Structural Defects in MOFs Using Water Stability

“…Defective MOFs typically possess larger pores and a greater surface area or pore volume, leading to increased adsorption. Wang et al used computation to study the effect of missing linkers on isopropyl alcohol (IPA) adsorption and diffusion in UiO-66 . Their results showed that missing linkers and the resulting larger accessible porous volume can lead to a larger adsorption capacity of IPA but that IPA binds more strongly with uncoordinated Zr in defective regions, which results in a much slower self-diffusion.…”

From Synthesis Conditions to UiO-66 Properties: Machine Learning Approach

“…Defects in UiO-66 introduce another dimension to its characterization and profoundly influence diffusion, , adsorption, ,− and catalytic properties. ,, The defects in UiO-66 are primarily of two types: missing linker defects and missing cluster defects . While the latter is harder to quantify and often detected by powder X-ray diffraction (PXRD), the former can be measured using methods like thermogravimetric analysis (TGA) and nuclear magnetic resonance (NMR), with TGA being the preferred choice for its straightforwardness. ,, …”

“…Similarly, particle size and morphology assessments using self-assembled monolayer (SEM) and transmission electron microscopy (TEM) are generally reliable, but the specifics of the methodology can impact the results. 90 Defects in UiO-66 introduce another dimension to its characterization 91 and profoundly influence diffusion, 92,93 adsorption, 92,94−96 and catalytic properties. 65,92,97 The defects in UiO-66 are primarily of two types: missing linker defects 98 and missing cluster defects.…”