Preparation of liquid marbles using an azobenzene-based metal-organic framework particles

We fabricated a metal-organic framework (MOF) using azobenzene containing dicarboxylic acid as an organic linker and Zn ion as nodes. The MOF was functionalized with polyhedral oligomeric silsesquioxane (POSS) to obtain highly hydrophobic propertyon the surface of the MOF. Such POSS-functionalized MOF was ground to fine particles and the resultant particles were used for the fabrication of liquid marbles (LMs) by dropping water on the finely-ground MOF. The LMs could be easily fabricated because of the hydrophobic nature of the POSS and could be used as stimuli-responsive materials. We founded that LMs decorated with the MOF lost their original shape upon exposure to acidic vapors because of the formation of protonatedazobenzene by the acidic vapor, leading to the hydrophilization of the surface of the MOF. This result reveals that the LM has the potential for the detection of acidic vapors.