Cation-Exchange Porosity Tuning in a Dynamic 4d–4f–3d Framework for NiII Ion-Selective Luminescent Probe

A heterometallic complex {[Yb2(L)6Cd2]­[Cd­(H2O)6]·6H2O}n (Yb–Cd) (H2L = oxidiacetic acid) was synthesized under hydrothermal conditions. In Yb–Cd, each L chelates to one Yb3+ center and bonds to two Cd2+ ions in an anti-anti configuration. Yb and Cd atoms are arrayed alternatively and connected by O–C–O bridges to form a cubic octahedral cage as the secondary building unit. Consequently, topological NaCl nets with high symmetry in the cubic space group Fd-3c have been constructed. The [Cd­(H2O)6]2+ moieties lying in the porosity of anionic metal–organic framework (MOF) act as the thermodynamically stable species, required to balance the two negative charges of [Yb2(L)6Cd2]2– in Yb–Cd. Interestingly, when Yb–Cd was employed as a precursor and emerged in the aqueous solution of Mn­(ClO4)2·6H2O or Zn­(ClO4)2·6H2O, a reversible single-crystal-to-single-crystal transformation process driven by [Cd­(H2O)6]2+ cations has been exhibited to generate the heterotrimetallic coordination polymer {[Yb2(L)6Cd2]­[Mn­(H2O)6]·6H2O}n (Yb–Cd–Mn) or {[Yb2(L)6Cd2]­[Zn­(H2O)6]·6H2O}n (Yb–Cd–Zn). To the best of out knowledge, Yb–Cd–Mn and Yb–Cd–Zn are the first examples representing 4d–4f–3d polymers based on multicarboxylic acid. Luminescent studies reveal that Yb–Cd–Zn may serve as a good candidate of Ni2+ a luminescent probe. To our knowledge, Yb–Cd–Zn represent the fist example of the 4d–4f–3d framework to exhibit luminescent selectivity for Ni2+.