Tailoring adsorption induced switchability of a pillared layer MOF by crystal size engineering

Abylgazina, Leila; Senkovska, Irena; Ehrling, Sebastian; Bon, Volodymyr; Petkov, Petko St.; Evans, Jack D.; Krylova, S. N.; Крылов, А. С.; Kaskel, Stefan

doi:10.1039/d0ce01497d

“…Type Ia characterizes narrow micropores of width <~1 nm, while type Ib is less steep and indicative of a broader pore-size distribution and some larger pores up to~2. are related to the composition (here the metal node), reflecting the different hinge energetics in terms of the activation barrier and latent heat (L) for closing the empty framework [29]. A rigidification through downscaling was also observed for DUT-98 [30].…”

Section: Box 2 Background Information On Adsorption Isothermsmentioning

confidence: 96%

“…Pronounced effects of crystal downsizing were observed for the prototypical gating framework DUT-8 [26][27][28][29]. DUT-8(M) loses framework flexibility and retains a metastable open pore structure after removal of guest molecules (Figure 2A) if the crystal size is below a critical dimension (d crit~5 00 nm for M = Ni and~200 nm for M = Zn).…”

Section: Trends In Chemistrymentioning

confidence: 99%

“…For the creation of the internal grain boundaries, the desolvation stress plays a critical role. A higher interaction of the solvent with the internal surface can easily contract even the nanocrystals while a mild supercritical desolvation will allow the retention of a metastable phase stabilized by surface effects [29]. It can be expected that the size of microdomains formed after desolvation (gate closing) is highly correlated with the surface tension (desorption stress) of the evaporating solvent and the removal rate.…”

Section: Trends In Chemistrymentioning

confidence: 99%

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From Macro- to Nanoscale: Finite Size Effects on Metal–Organic Framework Switchability

Ehrling

¹

,

Miura

²

,

Senkovska

³

et al. 2021

Trends in Chemistry

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Switchable metal-organic frameworks (MOFs) standt out for potential applications in energy storage, separation, sensing, and catalysis. The understanding of MOF switchability mechanisms has progressed significantly over the past two decades. Nanostructuring is essential for the integration of such materials into thin films, hierarchical composites, and membranes and for biological applications. However, downsizing below critical dimensions causes dramatic changes in the dynamic behavior and responsiveness towards external stimuli. We discuss the most important experimental findings and derive general guidelines and hypotheses of relevance for the impact of crystal size on switchability. Understanding nanostructure thermodynamics and implications for the tailoring of dynamic porous systems requires an interdisciplinary approach, advanced physical characterization techniques, and new modeling strategies to cover a wider range of time and length scales. MOF Switchability and FunctionalityMOFs are among the most porous systems, with great potential in diverse applications such as energy storage, separation, air purification, and many more [1,2]. An outstanding feature, compared with other, traditional porous materials, is their ability to transform (switch) between different phases with well-defined crystalline structures triggered by external stimuli, often by guest inclusion [3,4]. The latter leads, in some cases, to important improvements in gas separation or storage due to ultrahigh selectivity [5] or high deliverable capacity [6]. The terms 'flexible MOF', 'soft porous crystals', and 'switchable MOF' are used synonymously [7,8]. An important aspect indicated by the term 'switchability' is the stepwise (first order) character of the structural transition between two phases (bistability). Recently, even multistable systems have emerged, leading to remarkable recognition effects [9,10]. These phase transitions induced by external stimuli (e.g., changes in temperature, external pressure, gas pressure, vapor pressure, or electromagnetic radiation) are associated with a latent heat of transformation, L, governing the energetics of the bulk phase transition. An activation barrier (E A or ΔG ǂ ) governs the kinetics and potential windows for metastable states. Nucleation (for nucleation theory see Glossary and see supplemental information online for additional Glossary terms) of the new solid phase is an important characteristic of the solid-solid phase transition. Nevertheless, the fluid kinetics of adsorption and, potentially, fluid nucleation kinetics may also play a role. HighlightsSwitchable metal-organic frameworks (MOFs) conquer advanced applications in energy storage, sensing, gas separation, catalysis, and biomedicine. They benefit from unique adsorption characteristics and responsive behavior leading to anomalously high separation selectivity and deliverable storage capacity.Nanostructuring provides an effective means to tailor the responsive behavior of switchable MOFs. The characteristic switching pressure d...

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“…The exact reason for such phenomena is still a matter of investigation but similar behavior has been also reported for DUT-8(Zn). 23 A description of such phenomena in ordinary language requires nested if-clauses that create an aversion in the mind of the reader and are difficult to digest and memorize.…”

Section: Crystal Size and Morphologymentioning

confidence: 99%

Logic and Symbolism of Switchable Porous Framework Materials

Abylgazina¹,

Senkovska²,

Kaskel

³

2021

Preprint

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Metal-Organic Frameworks (MOFs) are highly porous materials composed of organic linkers connected by inorganic nodes. A unique subset of MOFs shows switchability, the ability to switch between at least two distinct structures differing significantly in porosity. These unique guest dependent pore opening and closing processes offer new opportunities in gas separation, selective recognition, sensing and energy storage. However, the factors affecting switchability are poorly understood. Network topology, micromechanics of building blocks and their hinges, but also particle size, defects, agglomeration, desolvation conditions etc. are convoluted into the responsiveness of the system. In essence all factors are a consequence of the materials history including synthesis procedure and desolvation but also all subsequent handling steps such as mechanical and adsorption stress leading to a complex interplay of factors which are difficult to express clearly by ordinary writing systems, chemical or mathematical symbols without loss of intuitive understanding. Here we propose a symbolic language for the rationalization of switchability emphasizing the history dependent responsivity of many dynamic frameworks and their stimuli induced 1st order phase transitions. Color representations of the guest and host offer an intuitive understanding of switchability phenomena even for non-experts. The system follows a bivalent logic inspired by Freges Begriffsschrift providing a fundamental logic structure for the rationalization of statements and representation of logic gates.

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“…Recently we reported the impact of framework desolvation on switchability for the model system DUT-8(Zn) and found a highly complex interdependence of particle size and activation conditions. 23 For simplification here we do not consider the particle size effects and only address the responsivity of the bulk material. We compare two different desolvation conditions namely solvent exchange with dichloromethane (DCM) followed by evacuation and supercritical exchange with CO2 and simplify the observations (Figure 4c,d).…”

Section: Framework Desolvation Dependent Responsivitymentioning

confidence: 99%

Logic and Symbolism of Switchable Porous Framework Materials

Abylgazina¹,

Senkovska²,

Kaskel

³

2021

Preprint

Self Cite

View full text Add to dashboard Cite

Metal-Organic Frameworks (MOFs) are highly porous materials composed of organic linkers connected by inorganic nodes. A unique subset of MOFs shows switchability, the ability to switch between at least two distinct structures differing significantly in porosity. These unique guest dependent pore opening and closing processes offer new opportunities in gas separation, selective recognition, sensing and energy storage. However, the factors affecting switchability are poorly understood. Network topology, micromechanics of building blocks and their hinges, but also particle size, defects, agglomeration, desolvation conditions etc. are convoluted into the responsiveness of the system. In essence all factors are a consequence of the materials history including synthesis procedure and desolvation but also all subsequent handling steps such as mechanical and adsorption stress leading to a complex interplay of factors which are difficult to express clearly by ordinary writing systems, chemical or mathematical symbols without loss of intuitive understanding. Here we propose a symbolic language for the rationalization of switchability emphasizing the history dependent responsivity of many dynamic frameworks and their stimuli induced 1st order phase transitions. Color representations of the guest and host offer an intuitive understanding of switchability phenomena even for non-experts. The system follows a bivalent logic inspired by Freges Begriffsschrift providing a fundamental logic structure for the rationalization of statements and representation of logic gates.

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Tailoring adsorption induced switchability of a pillared layer MOF by crystal size engineering

Abstract: The pillared layer framework DUT-8(Zn) (Zn2(2,6-ndc)2(dabco), 2,6-ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo-[2.2.2]-octane, DUT = Dresden University of Technology) is a prototypical switchable MOF, showing characteristic adsorption and desorption induced open...

Cited by 32 publications

References 72 publications

From Macro- to Nanoscale: Finite Size Effects on Metal–Organic Framework Switchability

From Macro- to Nanoscale: Finite Size Effects on Metal–Organic Framework Switchability

Logic and Symbolism of Switchable Porous Framework Materials

Logic and Symbolism of Switchable Porous Framework Materials

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