A new cationic silver(I)/melamine coordination polymer, [Ag2(melamine)]n2n+: Synthesis, characterization and potential use for aqueous contaminant anion exchange

Abstract

A new cationic Ag(I)-melamine coordination polymer (AgM-CP), [Ag2(melamine)(CH3CO2)(NO3)]n, was synthesized in acidic aqueous solution and characterized via FTIR, Raman, SEM/EDX, SC-XRD, PXRD, and BET. SC-XRD and Raman reveal that melamine acts as tridentate ligand towards three different Ag (I) through the three triazine-nitrogen atoms. Raman results confirm the crystalline nature of AgM-CP as given by SC-XRD. Raman and FTIR, together, confirm the formation of coordination bonds between the electron-donor nitrogen atoms and the electron-acceptor silver(I). SEM shows that AgM-CP has a bar-like macro-structure with considerably large dimensions, e.g. 220 μm. AgM-CP structure is suggested to be cationic, and highly water-stable as concluded from weight loss calculations, PXRD, and Raman analyses. Due to these properties, AgM-CP was examined for the selective removal of anionic methyl orange (MO−) competitively with the cationic methylene blue (MB+) using aqueous solution of these synthetic dyes. MO− was almost completely removed (95 mg g−1 under the specified initial concentration) with no significant removal of MB+, which encourages its use as a material for the selective removal of the anionic contaminants from wastewater.