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.