Unprecedented Second-Timescale Blue/Green Emissions and Iodine-Uptake-Induced Single-Crystal-to-Single-Crystal Transformation in ZnII/CdII Metal-Organic Frameworks

The long-persistent phosphorescent metal-organic framework (MOF) is a kind of highly desirable but rare material. Here, two new molecular MOF materials, {[Zn(tipa)Cl]center dot NO3 center dot 2DMF}(n) (1) and {[Cd-2(tipa)(2)Cl-4]center dot 6DMF}(n) (2) (tipa = tri(4-imidazolylphenyl)amine), which have 3D twofold interpenetrated (utp) and 2D noninterpenetrated (kgd) topologies, respectively, are reported. They exhibit unexpected long-persistent emissions yet reported: At 77 K, they persist in glowing after stopping the UV irradiation on a timescale up to seconds at 77 K, which can be detected by the naked eye (ca. 2 s). Compounds 1 and 2 also undergo single-crystal-to-single-crystal (SC-SC) transformations through different routes; a simple anion-exchange route for 1 and a complicated replacement of mu(1)-Cl- ions by DMF molecules accompanying I-3(-) captured in the void for 2.