Reversible tuning of pore size and CO<sub>2</sub>adsorption in azobenzene functionalized porous organic polymers

Metal‐organic frameworks (MOFs) are nanoporous, crystalline hybrid materials, which enable various functionalities by incorporating functional organic molecules. By using organic linker molecules that possess photoswitchable azobenzene side groups, the remote control over certain properties was introduced to MOFs. Different MOF materials in the form of powders and thin films have been used to demonstrate the photoswitching. The applications of these stimuli‐responsive nanoporous solids range from switching the adsorption capacity of various gases over remote‐controlled release of guest molecules to continuously tunable membrane separation of molecular mixtures. A particular focus of this review is the effect of the azobenzene photoswitching on the host‐guest interaction, enabling smart applications of the material. Steric hindrance, which may suppress the photoswitching in some MOF structures, is also discussed.

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Section: Covalent Organic Framework With Azobenzene Side Groupsmentioning

confidence: 99%

Stimuli‐Responsive Metal‐Organic Frameworks with Photoswitchable Azobenzene Side Groups

Kanj

Müller

Heinke

2017

Macromol. Rapid Commun.

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“…Furthermore, photoswitchable molecular scaffolds20 and gel assemblies21 were realized utilising azobenzene photoisomerization. Also, for MOFs in the form of powders or thin films, photoswitchable moieties222324 were used to demonstrate the remote-control of the MOF properties like colour25, release262728 and adsorption2930313233 of the guest molecules, in particular of CO 2 (refs 32, 33). While in most cases illumination with ultraviolet-light was needed, linker molecules that can be switched with visible light were used for the MOF preparation recently34.…”

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confidence: 99%

Tunable molecular separation by nanoporous membranes

et al. 2016

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Metal-organic frameworks offer tremendous potential for efficient separation of molecular mixtures. Different pore sizes and suitable functionalizations of the framework allow for an adjustment of the static selectivity. Here we report membranes which offer dynamic control of the selectivity by remote signals, thus enabling a continuous adjustment of the permeate flux. This is realized by assembling linkers containing photoresponsive azobenzene-side-groups into monolithic, crystalline membranes of metal-organic frameworks. The azobenzene moieties can be switched from the trans to the cis configuration and vice versa by irradiation with ultraviolet or visible light, resulting in a substantial modification of the membrane permeability and separation factor. The precise control of the cis:trans azobenzene ratio, for example, by controlled irradiation times or by simultaneous irradiation with ultraviolet and visible light, enables the continuous tuning of the separation. For hydrogen:carbon-dioxide, the separation factor of this smart membrane can be steplessly adjusted between 3 and 8.

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“…Metal organic frameworks (MOFs) are a new class of materials that may serve as an ideal platform for the development of next-generation CO 2 capture materials due to their large capacity for the adsorption of gases as well as their structural and chemical tenability (Morris and Wheatley, 2008;Li et al, 2009;Simmons et al, 2011;Drage et al, 2012;Kenarsari et al, 2013;Sathre and Masanet, 2013;Huck et al, 2014;Wang et al, 2014;Erucar and Keskin, 2015;Nalaparaju et al, 2015;SerraCrespo et al, 2015). Despite the enthusiasm of the scientific community for MOFs and other nanoporous materials (Dawson et al, 2011;Wang et al, 2011;Duan et al, 2014;Zhu and Zhang, 2014) as solid adsorbents, solid adsorption is not considered a promising alternative for liquid absorption, in view that adsorption and regeneration batch processes are involved in solid adsorption, and efficient heat integration is very difficult. In our previous study (Liu et al, 2014), the separation of CO 2 from gas mixtures (i.e., CO 2 /H 2 , CO 2 /N 2 , and CO 2 /CH 4 ) using ZIF-8 in a glycol-2-methylimidazole (glycol-mIm) slurry was investigated.…”

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confidence: 99%

Large-scale synthesis of ZIF-67 and highly efficient carbon capture using a ZIF-67/glycol-2-methylimidazole slurry

Pan

Zhang

et al. 2015

Chemical Engineering Science

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Reversible tuning of pore size and CO₂adsorption in azobenzene functionalized porous organic polymers

Cited by 112 publications

References 41 publications

Stimuli‐Responsive Metal‐Organic Frameworks with Photoswitchable Azobenzene Side Groups

Stimuli‐Responsive Metal‐Organic Frameworks with Photoswitchable Azobenzene Side Groups

Tunable molecular separation by nanoporous membranes

Large-scale synthesis of ZIF-67 and highly efficient carbon capture using a ZIF-67/glycol-2-methylimidazole slurry

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Reversible tuning of pore size and CO2adsorption in azobenzene functionalized porous organic polymers

Cited by 112 publications

References 41 publications

Stimuli‐Responsive Metal‐Organic Frameworks with Photoswitchable Azobenzene Side Groups

Stimuli‐Responsive Metal‐Organic Frameworks with Photoswitchable Azobenzene Side Groups

Tunable molecular separation by nanoporous membranes

Large-scale synthesis of ZIF-67 and highly efficient carbon capture using a ZIF-67/glycol-2-methylimidazole slurry

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Product

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Reversible tuning of pore size and CO₂adsorption in azobenzene functionalized porous organic polymers