Photoinduced reversible switching of porosity in molecular crystals based on star-shaped azobenzene tetramers

The development of solid materials that can be reversibly interconverted by light between forms with different physico-chemical properties is of great interest for separation, catalysis, optoelectronics, holography, mechanical actuation and solar energy conversion. Here, we describe a series of shap...

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Bibliographic Details
Published in:Nature chemistry 2015-08, Vol.7 (8), p.634-640
Main Authors: Baroncini, Massimo, d'Agostino, Simone, Bergamini, Giacomo, Ceroni, Paola, Comotti, Angiolina, Sozzani, Piero, Bassanetti, Irene, Grepioni, Fabrizia, Hernandez, Taylor M., Silvi, Serena, Venturi, Margherita, Credi, Alberto
Format: Article
Language:English
Subjects:
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639/638/439
639/638/541/961
639/925/357/537
Analytical Chemistry
Biochemistry
Carbon dioxide
Catalysis
Chemical properties
Chemistry
Chemistry/Food Science
Crystals
Energy conversion
Holography
Inorganic Chemistry
Irradiation
Optical properties
Organic Chemistry
Physical Chemistry
Porosity
Solar energy
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Summary:The development of solid materials that can be reversibly interconverted by light between forms with different physico-chemical properties is of great interest for separation, catalysis, optoelectronics, holography, mechanical actuation and solar energy conversion. Here, we describe a series of shape-persistent azobenzene tetramers that form porous molecular crystals in their E -configuration, the porosity of which can be tuned by changing the peripheral substituents on the molecule. Efficient E → Z photoisomerization of the azobenzene units takes place in the solid state and converts the crystals into a non-porous amorphous melt phase. Crystallinity and porosity are restored upon Z → E isomerization promoted by visible light irradiation or heating. We demonstrate that the photoisomerization enables reversible on/off switching of optical properties such as birefringence as well as the capture of CO 2 from the gas phase. The linear design, structural versatility and synthetic accessibility make this new family of materials potentially interesting for technological applications. Rigid star-shaped azobenzene tetramers form a porous molecular crystal when the azobenzene moieties are in the trans configuration, and a non-porous amorphous material on their isomerization to the cis configuration. These two forms are reversibly interconverted in the solid state by light irradiation, thus enabling the photoswitching of optical and gas-capture properties.
ISSN:1755-4330
1755-4349
DOI:10.1038/nchem.2304