Direct synthesis of zeolitic imidazolate framework-8/chitosan composites in chitosan hydrogels

Zeolitic imidazolate framework-8 (ZIF-8)/chitosan composites were prepared in the chitosan hydrogels. The concentrations of the chitosan and the alkaline solution were varied to the synthesis of the ZIF-8/chitosan composites. In the chitosan hydrogels with the addition of ammonium hydroxide solution, the resulting ZIF-8 crystals exhibited an unusual XRD structure that the XRD peak at about 18 degrees (222) became the strongest. The XRD peak intensity ratio of (222)/(011) increased from 0.68 to 1.5-5.2 in the presence of chitosan hydrogels. ZIF-8/chitosan composites (FC2) were composed of aggregated nano-sized particles, and exhibited a higher CO2 adsorption than normal ZIF-8 crystals. After removing chitosan from FC2, XRD pattern of the resulting ZIF-8 crystals returned to the normal state and the morphology kept the same as the composite. (C) 2012 Elsevier Inc. All rights reserved.