A 2D Coordination Network That Detects Nitro Explosives in Water, Catalyzes Baylis-Hillman Reactions, and Undergoes Unusual 2D→3D Single-Crystal to Single-Crystal Transformation

The solvothermal reaction of Zn(NO3)(2)center dot 6H(2)0 and a linear dicarboxylate ligand H2L, in the presence of urotropine in N,N'-dimethylformamide (DMF), gives rise to a new porous two-dimensional (2D) coordination network, {[Zn-3(L)(3)(urotropine)(2)]-2DMF center dot 3H(2)O}(n) (1), with hxl topology. Interestingly, framework 1 exhibits excellent emission properties owing to the presence of naphthalene moiety in the linker H2L, that can be efficiently suppressed by subtle quantity of nitro explosives in aqueous medium. Furthermore, presence of urotropine molecules bound to the metal centers, 1 is found to be an excellent heterogeneous catalyst meant for atom-economical C C bond-forming Baylis Hillman reactions. Additionally, crystals of 1 undergo complete transmetalation with Cu(II) to afford isostruttutal lcu. Moreover, the 2D framework of 1 allows replacement of urotropine molecules by 4,4'-azopyridine (azp) linker resulting in a three-dimensional (3D) metal organic framework, {[Zn(L)(azp)]center dot 4DMF 2H(2)O}(n) (2). The 1 -> 2 transformation takes place in single-crystal-to-single crystal manner supported by powder X-ray diffraction, atomic force microscopy, high-resolution transmission electron microscopy, and, morphological studies. Remarkably, during this 2D -> 3D transformation, the original trinuclear [Zn-3(COO)(6)] secondary building unit change's to a mononuclear node, which is unprecedented.