A Eu3+ post-functionalized metal-organic framework as fluorescent probe for highly selective sensing of Cu2+ in aqueous media

A 3D microporous metal-organic framework Al(OH)(bpydc) (MOF-253, bpydc = 2,2′-bipyridyl-5,5′-dicarboxylic acid) containing uncoordinated bipyridyl groups was synthesized and structurally characterized. Then the uncoordinated bipyridyl groups were used as postsynthetic modification sites to encapsulate Eu3+ cations into the pores of MOF-253. The intense luminescence of Eu3+ incorporated MOF-253 products Eu3+@MOF-253 indicates that the framework is rigid, permanently porous and non-coordinated bipyridyl groups are efficient scaffolds for hosting and sensitizing Eu3+ cations. Photoluminescence measurement demonstrates that Eu3+@MOF-253 displays excellent selectivity, and high sensitivity (detection limit, 0.66 μM) for Cu2+ ions in aqueous solution due to a great depression of the Eu3+-luminescence, which represents a rare Cu2+ fluorescent probe based on lanthanide-loaded MOFs constructed by postsynthetic method (PSM).