Hydrothermal assembly, structures, topologies, luminescence, and magnetism of a novel series of coordination polymers driven by a trifunctional nicotinic acid building block

Layer by Layer Spraying Fabrication of Aggregation-Induced Emission Metal-Organic Frameworks Thin Film

The development of new metal-organic frameworks (MOFs) thin films is important for expanding their functions and applications. Herein, we first report a new kind of MOF thin film by using aggregation-induced emission (AIE) dicarboxyl ligand through a liquid-phase epitaxial (LPE) layer-by-layer (LBL) spraying method (named AIE surface-coordinated metal-organic frameworks thin film, AIE-SURMOF). The obtained AIE-SURMOF Zn4O(TPE)3 (ZnTPE) has highly growth orientation and homogeneous thin film, showing strong fluorescent property. Furthermore, by loading chiral guest in the MOF pore, the formed chiral encapsulated AIE-SURMOF can clearly indicate obvious circularly polarized luminescence performance with glum of 0.01. This study provides new MOF thin film and new strategy for expanding function and application of MOF materials.

Synthesis and Fluorescent Characteristics Study of Two Novel Co(II) Complexes

In this work, two novel mixed-ligand CPs that has a compositions of [Co2(µ-Hdppa)2(phen)2(H2O)2] (1) and {[Co(µ-Hdppa)(µ-4,4'-bipy)(H2O)]·H2O}n (2) is achieved through reaction of cobalt salts with the 5-(3,4-Dicarboxylphenyl)picolinic acid (H3dppa) with various N-donor co-ligands (1,10-phenanthroline (phen) for 1 and 4,4'-bipyridine (4,4'-bipy) for 2). The structures and characteristics of these two complexes were fully examined via IR, TGA, and SXRD. Furthermore, their superior blue fluorescence properties compared to the original ligands were confirmed through fluorescence spectroscopy. These two complexes prepared in this study have enriched the choices for blue fluorescent materials.

Coordination Polymers from an Amino-Functionalized Terphenyl-Tetracarboxylate Linker: Structural Multiplicity and Catalytic Properties

An amino-functionalized terphenyl-tetracarboxylic acid, 2'-amino-[1,1':4',1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid (H4tpta), was used as an adaptable linker to synthesize, under hydrothermal conditions, eight coordination polymers (CPs). The obtained products were formulated as [Co(μ6-H2tpta)]n (1), [Co(μ3-H2tpta)(2,2'-bipy)]n (2), [M3(μ6-Htpta)2(2,2'-bipy)2]n (M = Mn (3), Cd (4)), [Ni2(μ4-tpta)(phen)2(H2O)4]n (5), [Zn2(μ6-tpta)(phen)2]n (6), {[Zn2(μ6-tpta)(μ-4,4'-bipy)]·H2O}n (7), and [Zn2(μ6-tpta)(μ-H2biim)(H2O)2]n (8), wherein 2,2'-bipyridine (2,2'-bipy), 4,4'-bipyridine (4,4'-bipy), 1,10-phenanthroline (phen), or 2,2'-biimidazole (H2biim) are present as additional stabilizing ligands. The structural types of 1-8 vary from one-dimensional (1D) (2, 5) and two-dimensional (2D) (3, 4, 6) CPs to three-dimensional (3D) metal-organic frameworks (MOFs) (1, 7, and 8) with a diversity of topologies. The products 1-8 were investigated as catalysts in the Knoevenagel condensation involving aldehydes and active methylene derivatives (malononitrile, ethyl cyanoacetate, or tert-butyl cyanoacetate), leading to high condensation product yields (up to 99%) under optimized conditions. Various reaction conditions, substrate scope, and catalyst recycling were investigated. This work broadens the application of H4tpta as a versatile tetracarboxylate linker for the generation of diverse CPs/MOFs.

New Transition Metal Coordination Polymers Derived from 2-(3,5-Dicarboxyphenyl)-6-carboxybenzimidazole as Photocatalysts for Dye and Antibiotic Decomposition

Coordination polymers (CPs) are an assorted class of coordination complexes that are gaining attention for the safe and sustainable removal of organic dyes from wastewater discharge by either adsorption or photocatalytic degradation. Herein, three different coordination polymers with compositions [Ni(HL)(H2O)2·1.9H2O] (1), [Mn3(HL)(L)(μ3-OH)(H2O)(phen)2·2H2O] (2), and [Cd(HL)4(H2O)]·H2O (3) (H3L = 2-(3,5-dicarboxyphenyl)-6-carboxybenzimidazole; phen = 1,10-phenanthroline) have been synthesized and characterized spectroscopically and by single crystal X-ray diffraction. Single crystal X-ray diffraction results indicated that 1 forms a 2D layer-like framework, while 2 exhibits a 3-connected net with the Schläfli symbol of (44.6), and 3 displays a 3D supramolecular network in which two adjacent 2D layers are held by π···π interactions. All three compounds have been used as photocatalysts to catalyze the photodegradation of antibiotic dinitrozole (DTZ) and rhodamine B (RhB). The photocatalytic results suggested that the Mn-based CP 2 exhibited better photodecomposition of DTZ (91.1%) and RhB (95.0%) than the other two CPs in the time span of 45 min. The observed photocatalytic mechanisms have been addressed using Hirshfeld surface analyses.

Coordination Polymers from Biphenyl-Dicarboxylate Linkers: Synthesis, Structural Diversity, Interpenetration, and Catalytic Properties

The present work explores two biphenyl-dicarboxylate linkers, 3,3'-dihydroxy-(1,1'-biphenyl)-4,4'-dicarboxylic (H4L1) and 4,4'-dihydroxy-(1,1'-biphenyl)-3,3'-dicarboxylic (H4L2) acids, in hydrothermal generation of nine new compounds formulated as [Co2(μ2-H2L1)2(phen)2(H2O)4] (1), [Mn2(μ4-H2L1)2(phen)2]n·4nH2O (2), [Zn(μ2-H2L1)(2,2'-bipy)(H2O)]n (3), [Cd(μ2-H2L1) (2,2'-bipy)(H2O)]n (4), [Mn2(μ2-H2L1)(μ4-H2L1)(μ2-4,4'-bipy)2]n·4nH2O (5), [Zn(μ2-H2L1)(μ2-4,4'-bipy)]n (6), [Zn(μ2-H2L2)(phen)]n (7), [Cd(μ3-H2L2)(phen)]n (8), and [Cu(μ2-H2L2) (μ2-4,4'-bipy)(H2O)]n (9). These coordination polymers (CPs) were generated by reacting a metal(II) chloride, a H4L1 or H4L2 linker, and a crystallization mediator such as 2,2'-bipy (2,2'-bipyridine), 4,4'-bipy (4,4'-bipyridine), or phen (1,10-phenanthroline). The structural types of 1-9 range from molecular dimers (1) to one-dimensional (3, 4, 7) and two-dimensional (8, 9) CPs as well as three-dimensional metal-organic frameworks (2, 5, 6). Their structural, topological, and interpenetration features were underlined, including an identification of unique two- and fivefold 3D + 3D interpenetrated nets in 5 and 6. Phase purity, thermal and luminescence behavior, as well as catalytic activity of the synthesized products were investigated. Particularly, a Zn(II)-based CP 3 acts as an effective and recyclable heterogeneous catalyst for Henry reaction between a model substrate (4-nitrobenzaldehyde) and nitroethane to give β-nitro alcohol products. For this reaction, various parameters were optimized, followed by the investigation of the substrate scope. By reporting nine new compounds and their structural traits and functional properties, the present work further outspreads a family of CPs constructed from the biphenyl-dicarboxylate H4L1 and H4L2 linkers.

A Cu(II)-based coordination polymer: catalytic properties and treatment activity on stroke

A fresh Cu(II) coordination polymer, i.e., [Cu₃(Hmbdc)₂(mbdc)₂(dmphen)₂]_n (1, H₂mbdc = isophthalic acid, dmphen = 4,7-dimethyl-1,10-phenanthroline), has been generated with the hydrothermal reactions between Cu salts and the mixed ligands of 4,7-dimethyl-1,10-phenanthroline and isophthalic acid. Moreover, the catalytic activity of 1 was evaluated via degrading the Congo red with a method of Fenton with an excellent degradation efficiency of 95.8% at 100 min. Next, the application value of compound on stroke was assessed, and the related mechanisms were explored at the same time. First of all, the tumor necrosis factor-α and recombinant rat IL-1β content released into the plasma were determined with enzyme-linked immunosorbent assay detection kit. Besides, the activation of the HMGB1/TLR4 signaling pathway activation in cerebral vascular endothelial cells was also determined with real-time reverse transcription–polymerase chain reaction assay.

Zn(II) metal-organic architectures from ether-bridged tetracarboxylate linkers: assembly, structural variety and catalytic features

Semi-flexible aromatic polycarboxylic acids are gaining impetus in crystal engineering of functional coordination polymers (CPs). This work opens up the use of two ether-bridged tetracarboxylic acids, 3-(2,5-dicarboxyphenoxy)phthalic acid (H4dpa) and...

Single-crystal-to-single-crystal transformations among three Mn-MOFs containing different water molecules induced by reaction time: crystal structures and proton conductivities

Three Mn-MOFs {[Mn₃(μ₄-L)₂(H₂O)₇]·4H₂O}_n (1), {[Mn₃(μ₅-L)₂(H₂O)₆]·4H₂O}_n (2) and {[Mn₃(μ₇-L)₂(H₂O)₂]}_n (3) (H₃L = 5-(6-carboxypyridin-3-yl)isophthalic acid) were obtained under different reaction times and temperatures. Interestingly, induced by reaction time, compound 1 can lose one water molecule and SC-SC transform into compound 2. Similarly, compound 2 can also SC-SC transform into 3. Studies on two SC-SC transformation processes were carried out and the transformation mechanisms were deduced, which were verified by TG analyses. Different numbers of water molecules in the three compounds resulted in different coordination environments of the metal cation, coordination modes of the L^3- ligand, continuities of hydrogen bonds, dimensions of framework and porosities. The AC impendence spectra studies revealed that compounds 1-3 can enhance the proton conductivities of the Nafion composite membrane to about 47.77%, 36.88% and 21.28%, respectively. It is speculated that the highest proton conductivity of compound 1 may be due to its continuous hydrogen bond chain and highest water uptake, which were mainly decided by the number of water molecules.

Stereochemical Geometries and Photoluminescence in Pseudo-Halido-Zinc(II) Complexes. Structural Comparison between the Corresponding Cadmium(II) Analogs

Six pseudohalide zinc(II) containing a variety of N-donor auxiliary amines were structurally characterized. These include two mononuclear trigonal bipyramidal [Zn(NTB)(N3)]ClO4·½H2O (3) and [Zn(TPA)(NCS)]ClO4 (4), two distorted octahedral [Zn(1,8-damnph)2(dca)2] (5) and [Zn(8-amq)2(dca)2] (6a) as well as two 1D polymeric chains catena-[Zn(isq)2(μ1,5-dca)2] (7) and catena-[Zn(N,N-Me2en)2(μ1,5-dca)]dca (8), where NTB = tris(2-benzimidazolylmethyl)amine, TPA = tris(2-pyridylmethyl)amine, 1,8-damnph = 1,8-diaminonaphthalene, 8-amq = 8-amino-quinoline, isq = isoquinoline (isq) and N,N-Me2en = N,N-dimethylethylenediamine. In general, with the exception of 6 and 8, the complexes exhibited luminescence emission in MeOH associated with red shift of the emission maxima, and the strongest visible fluorescence peak was detected at 421 nm (λex = 330 nm) in the case of Complex 5.

Third-Order Nonlinear Optical Behavior of an Amide-Tricarboxylate Zinc(II) Metal-Organic Framework with Two-Fold 3D+3D Interpenetration

A new metal-organic framework (MOF), [Zn₄(μ₄-O)(μ₆-L)₂(H₂O)₂]_n·nDMF (ZSTU-10), was assembled from zinc(II) nitrate and N,N',N″-bis(4-carboxylate)trimesicamide linkers and fully characterized. Its crystal structure discloses an intricate two-fold 3D+3D interpenetrated MOF driven by the [Zn₄(μ₄-O)]-based tetragonal secondary building units and the C3-symmetric tris-amide-tricarboxylate linkers (μ₆-L^3-). Topological analysis of ZSTU-10 reveals two interpenetrated 3,6-connected nets with an rtl (rutile) topology. Z-Scan analysis at 532 nm was conducted to study a nonlinear optical (NLO) behavior of ZSTU-10. The nonlinear responses of ZSTU-10 were explored under various laser intensities, revealing notable third-order NLO properties in the visible region. A large two-photon absorption at lower incident intensities highlights the fact that ZSTU-10 can be applied in optical limiting devices as well as optical modulators. Moreover, a nonlinear refractive index (n₂) is indicative of a self-defocusing behavior. This work thus expands a family of novel MOF materials with remarkable optical properties.

Coordination Polymers in Dicyanamido-Cadmium(II) with Diverse Network Dimensionalities

The synthesis and structural characterization of six dicyanamido-cadmium(II) complexes are reported: catena-[Cd(μ1,3-dca)(μ1,5-dca)(3-ampy)] (1), catena-[Cd3(μ1,3,5-dca)2(μ1,5-dca)4(pyNO)2(H2O)2] (2), catena-{Cd(H2O)2(μ1,5-dca)2](2,6-lut-NO)} (3), catena-[Cd(Me2en)(μ1,5-dca)2] (4), catena-[Cd(Me4en)(μ1,5-dca)2] (5), and [Cd(1,8-damnp)2(dca)2] (6), where dca = dicyanamide anion, 3-ampy = 3-aminopyridine, pyNO = pyridine-N-oxide, 2,6-lut-NO = 2,6-lutidine-N-oxide, Me2en = N,N-dimethyl-ethylenediamine, Me4en = N,N,N′,N′-tetramethyl-ethylenediamine, and 1,8-damnp = 1,8-diaminonaphthaline. The coordination polymers have different dimensionalities: 1 and 5 form 3D networks structures; 3 and 4 form polymeric 1D chains and 1DD double chains, respectively. Ribbons of three fused polymeric chains are observed in 2. In 6, the mononuclear complex units form a hydrogen-bonded supramolecular 3D network. In the coordination polymer compounds, the dca linkers display three bonding modes: the most common μ1,5-dca and the least popular μ1,3- and μ1,3,5-dca bonding. The luminescence emission and thermal properties of the complexes were investigated.

Metal(II) Coordination Polymers from Tetracarboxylate Linkers: Synthesis, Structures, and Catalytic Cyanosilylation of Benzaldehydes

Three 2D coordination polymers, [Cu2(µ4-dpa)(bipy)2(H2O)]n∙6nH2O (1), [Mn2(µ6-dpa)(bipy)2]n (2), and [Zn2(µ4-dpa)(bipy)2(H2O)2]n·2nH2O (3), were prepared by a hydrothermal method using metal(II) chloride salts, 3-(2′,4′-dicarboxylphenoxy)phthalic acid (H4dpa) as a linker, as well as 2,2′-bipyridine (bipy) as a crystallization mediator. Compounds 1–3 were obtained as crystalline solids and fully characterized. The structures of 1–3 were established by single-crystal X-ray diffraction, revealing 2D metal-organic networks of sql, 3,6L66, and hcb topological types. Thermal stability and catalytic behavior of 1–3 were also studied. In particular, zinc(II) coordination polymer 3 functions as a highly active and recoverable heterogeneous catalyst in the mild cyanosilylation of benzaldehydes with trimethylsilyl cyanide to give cyanohydrin derivatives. The influence of various parameters was investigated, including a time of reaction, a loading of catalyst and its recycling, an effect of solvent type, and a substrate scope. As a result, up to 93% product yields were attained in a catalyst recoverable and reusable system when exploring 4-nitrobenzaldehyde as a model substrate. This study contributes to widening the types of multifunctional polycarboxylic acid linkers for the design of novel coordination polymers with notable applications in heterogeneous catalysis.

MOFs as Potential Matrices in Cyclodextrin Glycosyltransferase Immobilization

Cyclodextrins (CDs) and their derivatives have attracted significant attention in the pharmaceutical, food, and textile industries, which has led to an increased demand for their production. CD is typically produced by the action of cyclodextrin glycosyltransferase (CGTase) on starch. Owing to the relatively high cost of enzymes, the economic feasibility of the entire process strongly depends on the effective retention and recycling of CGTase in the reaction system, while maintaining its stability. CGTase enzymes immobilized on various supports such as porous glass beads or glyoxyl-agarose have been previously used to achieve this objective. Nevertheless, the attachment of biocatalysts on conventional supports is associated with numerous drawbacks, including enzyme leaching prominent in physical adsorption, reduced activity as a result of chemisorption, and increased mass transfer limitations. Recent reports on the successful utilization of metal-organic frameworks (MOFs) as supports for various enzymes suggest that CGTase could be immobilized for enhanced production of CDs. The three-dimensional microenvironment of MOFs could maintain the stability of CGTase while posing minimal diffusional limitations. Moreover, the presence of different functional groups on the surfaces of MOFs could provide multiple points for attachment of CGTase, thereby reducing enzyme loss through leaching. The present review focuses on the advantages MOFs can offer as support for CGTase immobilization as well as their potential for application in CD production.