Breathing Metal-Organic Frameworks Supported by an Arsenic-Bridged 4,4'-Bipyridine Ligand

Bent ligands bridged by heteroatoms have drawn significant interest as supramolecular coordination architectures. Traditionally, divalent group 16 elements are preferred over trivalent group 15 elements because of the anticipated steric hindrance. In this study, we explore metal-organic frameworks (MOFs) based on dipyridinoarsoles (DPAs), 4,4'-bipyridines bridged with an arsenic atom. An MOF with methyl-substituted DPA collapsed upon solvent removal, whereas that with phenyl-substituted DPA demonstrated breathing behavior due to guest molecule adsorption/desorption. In contrast, MOFs using the phosphorus analogue dipyridinophosphole exhibit inferior adsorption and lack breathing behavior. This is the first study to investigate the interplay among substituents, bridging elements, and dynamic behavior in MOFs using bent group 15 ligands.

Fabrication of a dual-emittingcomposite as a recyclable luminescent sensor for sensitive detection of nitrofuran antibiotics

A novel dual-emittingRhB@Zn-1composite was fabricated by encapsulating RhB into the channels ofZn-1, which can serve as a recyclable sensor for sensitive and selective detection of nitrofuran antibioticsviathe luminescence quenching process.

Polar Sulfone-Functionalized Oxygen-Rich Metal-Organic Frameworks for Highly Selective CO2 Capture and Sensitive Detection of Acetylacetone at ppb Level

A rational combination of an oxygen-rich pyridyl substituted tetrapodal ligand, tetrakis(4-pyridyloxymethylene)methane (TPOM), and a polar sulfone-functionalized conjugated bent dicarboxylate linker, dibenzothiophene-5,5'-dioxide-3,7-dicarboxylic acid (H₂(3,7-DBTDC)), with d¹⁰ metal centers, Zn(II) and Cd(II), has led to the construction of two new three-dimensional (3D) metal-organic frameworks,{[Zn₂(TPOM)(3,7-DBTDC)₂]·7H₂O·DMA}_n (1) and {[Cd₂(TPOM)(3,7-DBTDC)₂]·6H₂O·3DMF}_n (2). Single-crystal X-ray analysis indicates that 1 is a 3D framework with a dinuclear repeating unit having two different Zn(II) centers (tetrahedral and square pyramidal) and 2 is a 3D framework comprised of a dinuclear repeating unit with one crystallographically independent distorted pentagonal bipyramidal Cd(II) coordinated to chelating/bridging carboxylates and nitrogen atoms of the TPOM ligand. In both cases, the pores are aligned with oxygen atoms of the TPOM ligand and decorated with polar sulfone moieties. On the basis of the stability established by thermogravimetric analysis and powder X-ray diffraction (PXRD) and the presence of large solvent accessible voids (25.4% for 1 and 40.6% for 2), gas sorption studies of different gases (N₂, CO₂, and CH₄) and water vapor have been explored for both 1 and 2. The CO₂ sorption isotherm depicts type I isotherm with an uptake of 93.6 cm³ g^-1 (for 1) and 100.6 cm³ g^-1 (for 2) at 195 K. Additionally, sorption of CO₂ is highly selective over that of N₂ and CH₄ for both 1 and 2 due to the strong quadrupolar interactions between sulfone moieties and CO₂ molecules. Configurational bias Monte Carlo (CBMC) molecular simulation has further justified the highly selective CO₂ capture. On the other hand, the luminescence nature of 1 and 2 has been employed for highly selective detection of acetylacetone in aqueous methanol with a limit of 59 ppb in 1 and 66 ppb in 2, which are among the best reported values so far in the literature. The Stern-Volmer plots, spectral overlap, density functional theory calculations, CBMC simulation, and time-resolved lifetime measurements have been utilized for an extensive mechanistic study. The exclusive selectivity for acetylacetone in 1 and 2 have been confirmed by competitive selectivity test. Both exhibited good recyclability and stability after sensing experiments analyzed by fluorescence, PXRD, and field emission scanning electron microscopy studies.

Assembly of four new cobalt coordination polymers modulated by N-coligands: sensitive and selective sensing of nitroaromatics, Fe3+and Cr2O72−in water

Four new Co-CPs (1to4) have been obtained with the modulation of N-coligands.2and3can serve as multi-responsive sensors for rapid and sensitive detection of nitroaromatics, Fe³⁺and Cr₂O₇²⁻in water.

Metal-Organic Frameworks with Internal Urea-Functionalized Dicarboxylate Linkers for SO2 and NH3 Adsorption

Introduction of a urea R-NH-CO-NH-R group as a seven-membered diazepine ring at the center of 4,4'-biphenyl-dicarboxylic acid leads to a urea-functionalized dicarboxylate linker (L1^2-) from which four zinc metal-organic frameworks (MOFs) could be obtained, having a {Zn₄(μ₄-O)(O₂C-)₆} SBU and IRMOF-9 topology (compound [Zn₄(μ₄-O)(L1)₃], 1, from dimethylformamide, DMF) or a {Zn₂(O₂C-)₄} paddle-wheel SBU in a 2D-network (compound [Zn₂(L1)₂(DEF)₂·2.5DEF], 2, from diethylformamide, DEF). Pillaring of the 2D-network of 2 with 4,4'-bipyridine (bipy) or 1,2-bis(4-pyridyl)ethane (bpe) gives 3D frameworks with rhombohedrally distorted pcu-a topologies ([Zn₂(L1)₂(bipy)], 3 and [Zn₂(L1)₂(bpe)], 4, respectively). The 3D-frameworks 1, 3, and 4 are 2-fold interpenetrated with ∼50% solvent-accessible volume, albeit of apparently dynamic porous character, such that N₂ adsorption at 77 K does not occur, while H₂ at 77 K (up to ∼1 wt %) and CO₂ at 293 K (∼5 wt %) are adsorbed with large hystereses in these flexible MOFs. The urea-functionalized MOF 3 exhibits an uptake of 10.9 mmol g^-1 (41 wt %) of SO₂ at 293 K, 1 bar, which appears to be the highest value observed so far. Compounds 3 and 4 adsorb 14.3 mmol g^-1 (20 wt %) and 17.8 mmol g^-1 (23 wt %) NH₃, respectively, which is at the top of the reported values. These high uptake values are traced to the urea functionality and its hydrogen-bonding interactions to the adsorbents. The gas uptake capacities follow the specific porosity of the frameworks, in combination with pore aperture size and affinity constants from fits of the adsorption isotherms.

Assembly, structures, photophysical properties and photocatalytic activities of a series of coordination polymers constructed from semi-rigid bis-pyridyl-bis-amide and benzenetricarboxylic acid

Ten metal–organic coordination polymers 1–10 based on semi-rigid bis-pyridyl-bis-amide ligands have been synthesized. The fluorescence sensing and photocatalytic properties of 1–10 have been investigated.