UoC-7: A Bimetallic K-Zn-MOF with an Anionic Framework Based on Fluorinated Trimesate Ligands Exhibiting a Large CO2 Uptake

In solvothermal reactions of Zn(NO3)2×6H2O with K(H2mF-BTC) or K(H2dF-BTC) in DMF/ethanol or DMA/ethanol solvent mixtures, single crystals of the MOFs UoC-7(1F) and UoC-7(2F) were obtained crystallizing in the hexagonal space group P63/m (no. 176) (H3BTC: 1,3,5-benzenetricarboxylic acid; mF-/dF: mono-/difluoro; DMF: N,N-dimethylformamide; DMA: N,N-dimethylacetamide; UoC: University of Cologne). According to the general composition [(CH3)2NH2][K2Zn3(mF-/dF-BTC)3(H2O)]×solvent, UoC-7 consists of an anionic bimetallic framework. The charge is compensated by a (CH3)2NH2 + cation stemming from the (partial) hydrolysis of the solvent. The crystal structure shows large channels along the hexagonal [001] direction, which accommodate the cations as well as solvent molecules. Surface areas (SBET) of 2740 m2/g (UoC-7(1F)) and 1643 m2/g (UoC-7(2F)) were obtained from N2 sorption measurements. UoC-7 shows structural similarities to the MOF NKU-521 with a 5-(1H-tetrazol-5-yl)isophthalate linker. Both MOFs exhibit a 4,7,8T14 topology. Despite smaller channels in UoC-7 compared to NKU-521, the CO2 uptake is considerably higher (~164 cm3/g at 1 bar/293 K) being one of the highest CO2 uptakes observed up to now.

Polarity profiling of porous architectures: solvatochromic dye encapsulation in metal-organic frameworks

Metal-organic frameworks (MOFs) have gathered significant interest due to their tunable porosity leading to diverse potential applications. In this study, we investigate the incorporation of the fluorosolvatochromic dye 2-butyl-5,6-dimethoxyisoindoline-1,3-dione ([double bond, length as m-dash]Phth) into various MOF structures as a means to assess the polarity of these porous materials. As a purely inorganic compound, zeolite Y was tested for comparison. The fluorosolvatochromic behavior of Phth, which manifests as changes in its emission spectra in response to solvent polarity, provides a sensitive probe for characterizing the local environment within the MOF pores. Through systematic variation of the MOF frameworks, we demonstrate the feasibility of using (fluoro-)solvatochromic dyes as probes for assessing the polarity gradients within MOF structures. Additionally, the fluorosolvatochromic response was studied as a function of loading amount. Our findings not only offer insights into the interplay between MOF architecture and guest molecule interactions but also present a promising approach for the rational design and classification of porous materials based on their polarity properties.

Suppression of Disorder in Benzamide and Thiobenzamide Crystals by Fluorine Substitution

Disorder is a common feature of molecular crystals that complicates determination of structures and can potentially affect electric and mechanical properties. Suppression of disorder is observed in otherwise severely disordered benzamide and thiobenzamide crystals by substituting hydrogen with fluorine in the ortho-position of the phenyl ring. Fluorine occupancies of 20-30% are sufficient to suppress disorder without changing the packing motif. Crystal structure prediction calculations reveal a much denser lattice energy landscape for benzamide compared to 2-fluorobenzamide, suggesting that fluorine substitution makes disorder less likely.

UoC-6: a first MOF based on a perfluorinated trimesate ligand

Reaction of Sc(NO3)3·5H2O with K(H2 pF-BTC) – the monopotassium salt of perfluorinated trimesic acid – led to the formation of single crystals of [ Sc ( p F − BTC ) ( H 2 O ) 3 ] ∞ 1 ⋅ 4 H 2 O ${}_{\infty }{}^{1}\left[\text{Sc}\left(pF-\text{BTC}\right){\left({\text{H}}_{2}\text{O}\right)}_{3}\right]\cdot 4{\text{H}}_{2}\text{O}$ ( P 1 ‾ $P‾{1}$ , Z = 2). DTA/TGA measurements revealed that all water molecules were released below 200 °C. Using powder synchrotron radiation diffraction data, the crystal structure of the residue of the dehydration was elucidated and the results confirmed the formula [ Sc ( p F − BTC ) ] ∞ 3 ${}_{\infty }{}^{3}\left[\text{Sc}\left(pF-\text{BTC}\right)\right]$ (Fddd, Z = 16). The compound is similar, but not isostructural to the recently published UoC-4 (I41/amd, Z = 8; UoC: University of Cologne) with a difluorinated trimesate (dF-BTC3–) as connecting linker. Both compounds can be classified as metal-organic frameworks (MOFs) consisting of a 3D network of Sc3+ nodes connected by the fluorinated trimesate ligands. They contain small pores, but their opening windows are too small for any guest molecules to pass. Remarkably, UoC-4 with a lower symmetric ligand (dF-BTC3–) crystallizes in a higher symmetry space group (I41/amd) than UoC-6 (Fddd). This can be rationalized by increasing torsion angles of the carboxylate moieties in the pF-BTC3– ligand.

The first coordination compound of 6-fluoro-nicotinate: the crystal structure of a one-dimensional nickel(II) coordination polymer containing the mixed ligands 6-fluoro-nicotinate and 4,4'-bi-pyridine

A one-dimensional nickel(II) coordination polymer with the mixed ligands 6-fluoro­nicotinate (6-Fnic) and 4,4′-bi­pyridine (4,4′-bpy), namely, [Ni(H₂O)₂(6-Fnic)₂(4,4′-bpy)·3H₂O]_n, (1), was prepared. The nickel(II) ion in 1 is octa­hedrally coordinated by the O atoms of two water mol­ecules, two O atoms from O-monodentate 6-fluoro­nicotinate ligands and two N atoms from bridging 4,4′-bi­pyridine ligands.

A one-dimensional nickel(II) coordination polymer with the mixed ligands 6-fluoro­nicotinate (6-Fnic) and 4,4′-bi­pyridine (4,4′-bpy), namely, catena-poly[[di­aqua­bis­(6-fluoro­pyridine-3-carboxyl­ato-κO)nickel(II)]-μ-4,4′-bi­pyri­dine-κ²N:N′] trihydrate], {[Ni(6-Fnic)₂(4,4′-bpy)(H₂O)₂]·3H₂O}_n, (1), was prepared by the reaction of nickel(II) sulfate hepta­hydrate, 6-fluoro­nicotinic acid (C₆H₄FNO₂) and 4,4′-bi­pyridine (C₁₀H₈N₂) in a mixture of water and ethanol. The nickel(II) ion in 1 is octa­hedrally coordinated by the O atoms of two water mol­ecules, two O atoms from O-monodentate 6-fluoro­nicotinate ligands and two N atoms from bridging 4,4′-bi­pyridine ligands, forming a trans isomer. The bridging 4,4′-bi­pyridine ligands connect symmetry-related nickel(II) ions into infinite one-dimensional polymeric chains running in the [10] direction. In the extended structure of 1, the polymeric chains and lattice water mol­ecules are connected into a three-dimensional hydrogen-bonded network via strong O—H⋯O and O—H⋯N hydrogen bonds, leading to the formation of distinct hydrogen-bond ring motifs: octa­meric R₈⁸(24) and hexa­meric R₈⁶(16) loops.

CFA-15 – a perfluorinated metal–organic framework with linear 1-D CuII-chains containing accessible unsaturated, reactive metal centres

The synthesis and crystal structure of the perfluorinated metal–organic framework CFA-15, CuII3(tfpc)₂(OH)₂·DMF, and the organic ligand H₂-tfpc, 3,5-bis(trifluoromethyl)-1H-pyrazole-4-carboxylic acid, are described.

A 2-D Metal–Organic Framework Based on Linear Trinuclear Copper Cluster Units: Syntheses, Structures and Magnetic Properties

The coordination polymer [Cu3(tci)2(phen)2] n (H3tci = 1,3,5-tris(2-carboxyethyl)isocyanurate; phen = 1,10-phenanthroline) has been synthesised. Single-crystal X-ray diffraction studies have shown that the polymer displays a 2-D metal–organic framework based on linear trinuclear copper cluster units, and its magnetic properties indicate antiferromagnetic interactions.

Crystal structure of catena-poly[aqua-(μ 2-hexamethylenetetramine-κ 2 N:N′)-bis(2,6-difluorobenzoato-κ 2 O:O′)cadmium(II)]monohydrate, C20H22CdF4N4O6

C20H22CdF4N4O6, orthorhombic, P212121 (no. 19), a = 7.475(3) Å, b = 12.246(5) Å, c = 24.615(11) Å, V =2253.0(17) Å3, Z = 4, R gt(F) = 0.0245, wR ref(F 2) = 0.0706, T = 296(2) K.

Crystal structure of catena-poly[(μ 2-hexamethylenetetramine-κ 2 N:N′)-tetrakis(μ 2-2,6-difluorobenzoato-κ 2 O:O′)dicopper(II)], C34H24Cu2F8N4O8

C34H24Cu2F8N4O8, monoclinic, P21/n (no. 14), a =13.074(3) Å, b = 20.229(4) Å, c = 14.419(3) Å, β = 108.889(2)°, V = 3608.2(12) Å3, Z = 4, R gt(F) = 0.0512, wR ref(F 2) = 0.1465, T = 296(2) K.

Ca- and Sr-tetrafluoroisophthalates: mechanochemical synthesis, characterization, and ab initio structure determination

New fluorinated coordination polymers were prepared mechanochemically by milling the alkaline earth metal hydroxides M^II(OH)₂·xH₂O (M^II: Ca, Sr) with tetrafluoroisophthalic acid (H₂mBDC-F₄). The structures of [{Ca(mBDC-F₄)(H₂O)₂}·H₂O] (1) and [{Sr(mBDC-F₄)(H₂O)₂}·H₂O] (2) were determined based on ab initio calculations and their powder X-ray diffraction (PXRD) data. The compounds are isomorphous and crystallize in the orthorhombic space group P2₁2₁2₁. The determined structures were validated by using extended X-ray absorption (EXAFS) data. The new materials were thoroughly characterized using elemental analysis, thermal analysis, magic angle spinning NMR, and attenuated total reflection-infrared spectroscopy. Further characterization methods such as BET, dynamic vapor sorption, and scanning electron microscopy imaging were also used. Our investigations indicate that mechanochemistry is an efficient method for preparing such materials.

Crystal structure of catenapoly[diaqua-(μ 24,4′-bipyridine)-κ 2 N:N′)-bis(2,6-difluorobenzoate)-κO)nickel(II)] ethanol monosolvate, C28H30F4N2O8Ni

C28H30F4N2O8Ni, Monoclinic, P2 1/n, a = 10.164(7) Å, b = 13.927(9) Å, c = 11.409(8) Å, β = 111.863(10) V = 1498.9(18) Å3, Z = 2, R gt (F) = 0.0389, wR ref (F 2 ) = 0.0957, T = 296(2) K.

Positive effect of the fluorine moiety on the oxygen storage capacity of UiO-66 metal–organic frameworks

The capacity to store oxygen and nitrogen within UiO-66 fluorine-containing MOFs has been tested through high pressure adsorption isotherms.

3,5-Bis((4′-carboxylbenzyl)oxy)benzoilate-based coordination polymers: their synthesis, structural characterization, and sensing properties

The structural characterization of four 3,5-bis((4′-carboxylbenzyl)oxy)benzoilate-based coordination polymers has been reported, and the sensing ability of 2 and 4 on NB has been investigated.