Porous flexible frameworks: origins of flexibility and applications

Seth, Saona; Jhulki, Samik

doi:10.1039/d0mh01710h

Cited by 68 publications

(60 citation statements)

References 182 publications

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“… 10 Flexible MOFs undergo temperature-influenced pressure-induced reversible phase transitions between an activated, dense phase with reduced accessible porosity and a gas-dosed, open phase with greater accessible porosity. 11–15 This behavior may manifest as a “step” in gas adsorption at the phase transition pressure ( Fig. 1 , blue curve).…”

Section: Introductionmentioning

confidence: 99%

Structural resolution and mechanistic insight into hydrogen adsorption in flexible ZIF-7

Klein

Shulda

Maguères³

et al. 2021

Chem. Sci.

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Section: Introductionmentioning

confidence: 99%

Structural resolution and mechanistic insight into hydrogen adsorption in flexible ZIF-7

Klein

Shulda

Maguères³

et al. 2021

Chem. Sci.

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“…A very exciting and important development in MOFs is the generation of flexible solids, also known as soft porous crystals (SPCs) . In these materials the structure can be altered in a reversible manner under specific external stimuli (e.g., host–guest interactions, temperature, and pressure), without bond breaking, while maintaining crystallinity. − These kinds of MOFs are currently representing a key direction in state-of-the-art MOF research, as control of this dynamic behavior opens novel pathways toward the development of adaptive and/or responsive materials for advanced applications, including selective gas storage, capture and separation, and fluorescence-based sensing, among others. − However, a limited number of flexible MOFs exist and are mainly based on first row transition metals and main group elements, where the observed dynamic behavior is associated with either ligand flexibility, a hinge-like motion of the coordinating groups, or network displacement in the case of interpenetrated MOFs. − …”

Section: Introductionmentioning

confidence: 99%

Continuous Breathing Rare-Earth MOFs Based on Hexanuclear Clusters with Gas Trapping Properties

et al. 2021

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Guest responsive porous materials represent an important and fascinating class of multifunctional solids that have attracted considerable attention in recent years. An understanding of how these structures form is essential toward their rational design, which is a prerequisite for the development of tailor-made materials for advanced applications. We herein report a novel series of stable rare-earth (RE) MOFs that show a rare continuous breathing behavior and an unprecedented gas-trapping property. We used an asymmetric 4-c tetratopic carboxylate-based organic ligand that is capable of affording highly crystalline materials upon controlled reaction with RE cations. These MOFs, denoted as RE-thc-MOF-1 (RE: Y3+, Sm3+, Eu3+, Tb3+, Dy3+, Ho3+, and Er3+), feature hexanuclear RE6 clusters that display a highly unusual connectivity and serve as unique 8-c hemi-cuboctahedral secondary building block, resulting in a new (3,3,8)-c thc topology. Extensive single-crystal to single-crystal structural analyses coupled with detailed gas (N2, Ar, Kr, CO2, CH4, and Xe) and vapor (EtOH, CH3CN, C6H6, and C6H14) sorption studies, supported by accurate theoretical calculations, shed light onto the unique swelling behavior. The results reveal a synergistic action involving steric effects, associated with coordinated solvent molecules and 2-fluorobenzoate (2-FBA) nonbridging ligands, as well as cation–framework electrostatic interactions. We were able to probe the individual role of the coordinated solvent molecules and 2-FBA ligands and found that both cooperatively control the gas-breathing and -trapping properties, while 2-FBA controls the vapor adsorption selectivity. These findings provide unique opportunities toward the design and development of tunable RE-based flexible MOFs with tailor-made properties.

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“…The structure of the crystalline material was established by single crystal structure analysis and the framework was found to possess sufficient Brønsted acidity to promote epoxide ring-openings and a Diels–Alder reaction . The study was a preliminary one but indicated that even F-1a , which does not possess significant pores, was able to absorb substrates by rearrangement of the matrix via a process called stimuli induced breathing . Still, it seemed self-evident that the porosity of a crystalline framework should be an important factor in making a heterogeneous catalyst much more efficient.…”

Section: Introductionmentioning

confidence: 99%

Inhibition by Water during Heterogeneous Brønsted Acid Catalysis by Three-Dimensional Crystalline Organic Salts

Gak

Kuznetsova

Nelyubina

et al. 2021

Crystal Growth & Design

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A new self-assembled and self-healing class of metal free, recyclable, heterogeneous Brønsted acid catalysts has been developed by the protonation of aniline derivatives (tetrakis(4aminophenyl)methane, leuco-crystal violet, benzidine, and p-phenylenediamine) with aromatic sulfonic acids (tetrakis(phenyl-4-sulfonic acid)methane, and 2,6-naphthalenedisulfonic acid). As a result, five three-dimensional crystalline organic salts (F-1a, F-1b, F-1c, F-2, and F-3) were obtained, linked by hydrogen bonds and additionally stabilized by the opposite charges of the components. Frameworks F-2 and F-3 were prepared for the first time and characterized by elemental analysis, X-ray structural analysis (for F-2), thermogravimetry, SEM, and FTIR spectroscopy. The catalytic activities of crystalline organic salts F-1−3 have been explored in industrially important epoxide ring-opening and acetal formation reactions. The presence of encapsulated water inside frameworks F-1a and F-2 had an inhibitory effect on the performance of the catalysts. Xray diffraction analysis of hydrated and dehydrated samples of F-1a and F-2 indicated that water of crystallization served as a crosslinking agent, diminishing the substrate induced "breathing" affinities of the frameworks.

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Porous flexible frameworks: origins of flexibility and applications

Abstract: All major classes of porous crystalline frameworks including zeolites, metal–organic frameworks, covalent organic frameworks and hydrogen-bonded organic frameworks exhibit structural flexibilities.

Cited by 68 publications

References 182 publications

Structural resolution and mechanistic insight into hydrogen adsorption in flexible ZIF-7

Structural resolution and mechanistic insight into hydrogen adsorption in flexible ZIF-7

Continuous Breathing Rare-Earth MOFs Based on Hexanuclear Clusters with Gas Trapping Properties

Inhibition by Water during Heterogeneous Brønsted Acid Catalysis by Three-Dimensional Crystalline Organic Salts

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