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

Abstract

The solvothermal reaction of Zn(NO)·6HO and a linear dicarboxylate ligand HL, in the presence of urotropine in N,N'-dimethylformamide (DMF), gives rise to a new porous two-dimensional (2D) coordination network, {[Zn(L)(urotropine)]·2DMF·3HO} (1), with hxl topology. Interestingly, framework 1 exhibits excellent emission properties owing to the presence of naphthalene moiety in the linker HL, 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 isostructural 1. 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)]·4DMF 2HO} (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(COO)] secondary building unit changes to a mononuclear node, which is unprecedented.

A Fluorogenic Triphenyl‐Amine‐Naphthyl‐Hydrazide Probe Selective for Cu2+ and Cysteine Detection via an ON‐OFF‐ON Logic path with Real Applications

“…The plot shows linearity upto 20 μM and accounts the static quenching and on above 20 μM of [Cu 2+ ] it shows an upward bend along with inclusion of dynamic process. The constancy of lifetime of the excited state fluorophore even on addition of Cu 2+ further confirms the static quenching [53,54] …”

“…The constancy of lifetime of the excited state fluorophore even on addition of Cu 2 + further confirms the static quenching. [53,54]…”

Engineered Bifunctional Luminescent Pillared‐Layer Frameworks for Adsorption of CO2 and Sensitive Detection of Nitrobenzene in Aqueous Media

“…The Stern–Volmer plots for MOFs 1 – 5 in water upon incremental addition of NB over the entire range of test concentrations (0–1.0 m m ) showed a deviation from a straight line with upward curvature, followed by quenching reaching a constant extent in the high‐concentration range (Figure S10 in the Supporting Information). This clearly specifies that the quenching process was caused by the cooperation of a dynamic energy‐transfer quenching mechanism, owing to collisions of NB molecules with the framework surface of MOFs 1 – 5 , and a static self‐absorption quenching mechanism, [8, 17, 68, 69] and there are limited accessible binding sites on the framework surfaces of MOFs 1 – 5 that could be in close contact with NB [31] . The K sv estimated from the linearity of I 0 / I versus [NB] gave a value of 2.93×10 3 m −1 in 0–100 μ m ( R 2 =0.99991) for 1 , 1.79×10 3 m −1 in 0–180 μ m ( R 2 =0.9999) for 2 , 3.78×10 3 m −1 in 0–360 μ m ( R 2 =0.99875) for 3 , 4.04×10 3 m −1 in 0–130 μ m ( R 2 =0.99927) for 4 , and 3.21×10 3 m −1 in 0–130 μ m ( R 2 =0.99962) for 5 (Figure 4, insets), suggesting a strong quenching effect on fluorescence.…”

Fluorescent Cadmium Bipillared‐Layer Open Frameworks: Synthesis, Structures, Sensing of Nitro Compounds, and Capture of Volatile Iodine

“…This envisionsafertile and exciting field for luminescent MOFs as potentialc hemosensors in sensitive and selectivee xplosive sensing. [7][8][9][10][11][20][21][22][23][24][25][26][27][28][29][30][31][32] On the other hand, one aspect of current MOF studiesi sf ocused on trace elemente nrichment and adsorption, such as iodine( I 2 ). [33][34][35][36][37][38][39][40][41][42][43][44][45][46] Iodinei sag aseous fission productl iberated duringt he reprocessingo fs pent nuclear fuel, [42,47] and thusi s considered as am ajor waste of the nuclear industries.…”

“…A wide range of luminescent MOFs have been explored for hazardous chemical sensing, including, but not limited to, the detection of heavy metal ions, anions, small organic molecules, toxic gases, and even biomacromolecules through achievable light‐emitting color change or fluorescence quenching/enhancement responses in either liquid‐phase detection or vapor‐phase sensing or both. This envisions a fertile and exciting field for luminescent MOFs as potential chemosensors in sensitive and selective explosive sensing …”