Data di Pubblicazione:
2018
Abstract:
We study the effect of synthesis time and temperature on the crystal formation, morphology and size of zeolitic
imidazolate frameworks (ZIFs) with the Zn(Im)2 composition by using the solution mixing method. The crystal
structure, morphology and thermodynamic properties of the ZIFs were characterized by powder X-ray diffraction,
scanning electron microscopy and nitrogen sorption isotherms. Our results indicate that the synthesis time
significantly influences the structure and topology of crystal products. The crystal structure transforms from ZIFcoi
to the progressively denser polymorphs (ZIF-zec, ZIF-nog and ZIF-zni) upon increasing synthesis time from
18 to 120 hours at 10 °C, in accordance with Ostwald's step rule. Increasing synthesis temperature does not
change the formation of the ZIF-zec crystals but affects their morphologies and porosities. Both ZIF-nog and ZIFzec
exhibit relatively large surface areas (> 500m2/g). Furthermore, heating ZIF-nog and ZIF-zec causes recrystallization
to ZIF-zni and subsequent melting. Quenching the MOF-liquid results in Zn(Im)2 glass. This work
helps to understand and control the crystal formation of ZIFs, and reveals two new MOF glass formers.
Tipologia CRIS:
03A-Articolo su Rivista
Keywords:
MOF glass; Morphology; Porosity; Synthesis conditions; Zeolitic imidazolate framework; Chemistry (all); Materials Science (all); Condensed Matter Physics; Mechanics of Materials
Elenco autori:
Zhou, Chao; Stepniewska, Malwina; Sørensen, Jens Martin; Scarpa, Luca; Magnacca, Giuliana; Boffa, Vittorio; Bennett, Thomas D.; Yue, Yuanzheng*
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