Two-Dimensional Cu-Based MOF for Selective Staining of the Cellular Nucleus through Fluorescence Imaging and Selective Sorption of Dye Molecules in Aqueous Medium.

A two-dimensional copper-based metal-organic framework, [Cu(C 23 H 14 O 6 )(C 10 H 8 N 2 ) 2 ]·H 2 O·DMSO, 1 , was synthesized using pamoic acid (C 23 H 16 O 6 ) and 4,4'-bipyridine (C 10 H 8 N 2 ) as an organic ligand and Cu(II) as a metal ion. Single-crystal structure X-ray diffraction studies of the as-synthesized compound showed a two- dimensional structure with free hydroxyl groups. Upon excitation at 370 nm, the aqueous dispersion of [Cu(C 23 H 14 O 6 )(C 10 H 8 N 2 ) 2 ]·H 2 O·DMSO, 1 , showed emission centered at 525 nm resulting from the intraligand energy transfer. Fluorescence microscopic experiments using a human epithelioid cervix carcinoma HeLa cell line were carried out, clearly showing that our compound selectively stained the cellular nucleus. To utilize the porous nature of [Cu(C 23 H 14 O 6 )(C 10 H 8 N 2 ) 2 ]·H 2 O·DMSO, 1 , its dye sorption behavior in aqueous solution was determined, and a high affinity for methylene blue (MB) dye was confirmed. Our synthesized compound sorbed 88% MB dye with an initial concentration of 32 mg L -1 , and its sorption capacity for MB was found to be 29.79 mg g -1 . The possible mechanism of the dye sorption behavior was discussed in terms of the size and charge of dye molecules with respect to molecular-level interactions between the framework and the dye molecules.