Selective Adsorption Properties of Cationic Metal–Organic Frameworks Based on Imidazolic Linker

In this work we propose an approach for the controlled
synthesis
of cationic frameworks by the use of imidazolium salts as linker molecules.
The imidazolium salt linker H2ImidCl was prepared in five
steps and converted with zinc and copper nitrate, respectively, to
give the two topologically different cationic frameworks [Cu­(Imid)­(H2O)]+ and [Zn4(Imid)5]3+. The framework charge is compensated by anions located in
the pores. [Cu­(Imid)­(H2O)]+ shows a selective
adsorption of organic molecules either bearing a carboxylic group
or having an ionic nature. Furthermore, adsorbed molecules featuring
a carboxylic group are captured inside the pores, whereas ionic substances
can be reversibly adsorbed and desorbed, which was followed by UV/vis
spectroscopy.