Unprecedented Second‐Timescale Blue/Green Emissions and Iodine‐Uptake‐Induced Single‐Crystal‐to‐Single‐Crystal Transformation in Zn II /Cd II 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] ⋅ NO 3 ⋅ 2 DMF} n ( 1 ) and {[Cd 2 (tipa) 2 Cl 4 ] ⋅ 6 DMF} 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 μ 1 ‐Cl − ions by DMF molecules accompanying I 3 − captured in the void for 2 .