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

Abstract

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 H 2 ImidCl was prepared in five steps and converted with zinc and copper nitrate, respectively, to give the two topologically different cationic frameworks [Cu(Imid)(H 2 O)] + and [Zn 4 (Imid) 5 ] 3+ . The framework charge is compensated by anions located in the pores. [Cu(Imid)(H 2 O)] + 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.

Emerging adsorptive removal of azo dye by metal–organic frameworks

“…The role of electrostatic interaction was well shown in the study by Nickerl et al on the selective adsorption of dyes using imidazolic linker-based cationic MOF, [Cu(Imid)(H 2 O)] þ (Nickerl et al, 2013). They selected Fluorescein (FR), Methyl Red (MR), Nile Blue (NB) and Nile Red (NR) to the azo dyes studied.…”

“…As mentioned in the table, the pseudo-second-order model mostly fitted the kinetic data well for the studied adsorption of azo dyes onto MOFs rather than other models and the theoretical q e values Scheme 7. Adsorption and desorption behavior of dyes over [Cu(Imid)(H 2 O)] (Nickerl et al, 2013). Hui and Yan (Huo and Yan, 2012) investigated the timedependent adsorption capacity through the kinetic study of MG adsorption over MIL-100(Fe) (see Fig.…”

Selective anion exchange with nanogated isoreticular positive metal-organic frameworks

“…Here we are particularly interested in the separation of organic anions. Among reported MOFs, there are comparatively few permanently porous MOFs with positive framework (P-MOFs) 6,36,37 , whose rarity is also mirrored in other types of porous materials, including zeolites [38][39][40][41][42][43][44][45] . In addition, known P-MOFs often have low stability or small pore size that only permits the exchange of small inorganic anions 7,10 .…”

Metal–organic frameworks containing N-heterocyclic carbenes and their precursors

“…Also, the open metal sites and counterions augment this selectivity in the pore cavities [125]. The charged azolium moieties interact more with polar organic molecules (such as polar dyes), which can be useful for their separation [128].…”

“…As outlined in Scheme 1(a) and discussed below, the imidazoliumcontaining ligands for MOF synthesis can be categorized as having Reproduced with permission from [154]. two design features [144]: (1) where the azolium or NHC entities form the core of the ligand [126,128,144] and (2) where the azolium or NHC entities are appended to existing linkers [141].…”