A polyrotaxane-like metal-organic framework exhibiting luminescent sensing of Eu3+ cations and proton conductivity

A novel microporous metal-organic framework (MOF), namely {[Cd2L3(DMF)(NO3)]center dot 2DMF center dot 3H(2)O}(n) (1), where L = 1,3-bis(4-carboxyphenyl) imidazolium chloride, was prepared via a hydrothermal process. The structure of 1 shows the first example of 6-fold polyrotaxane-like interpenetration combined with interdigitation which extends the structure into a three-dimensional framework and exhibits reversible and irreversible guest-dependent structural conversion; because of the 1D channels running along the b axis, 1 can serve as a host to encapsulate and sensitize Eu3+ cations in water. Moreover, the framework also exhibits a proton conductivity of over 10(-5) S cm(-1) at 298 K and 98% relative humidity because the methylene hydrogens of the imidazolium moiety are highly acidic and aligned inside the channels enhancing the proton conductivity.