Sequestration of orange G and methylene blue from aqueous solutions using a Co(II) coordination polymer

A Co(II) coordination polymer known for its crystalline sponge properties (CoSP) is used to sequester Orange G (OG) and methylene blue (MB) in aqueous solutions. Its ability to encapsulate the cationic MB is much greater than for OG. The CoSP material is notable for its structural transformations under different conditions (i.e. removal from solvent or immersion in alternative solvent systems) giving rise to both 3D and 2D networks. Herein, we study the activated semi-amorphous Co sponge (a-CoSP) as a host in aqueous solutions and find that guest uptake results in increased crystallinity as evidenced by powder X-ray diffraction (PXRD). Reactivation releases some dye due to decomposition of the coordination polymer however, the solubility of the building blocks in solution enables the reconstruction of the sponge.