Application of Functionalized Zn-Based Metal-Organic Frameworks (Zn-MOFs) with CuO in Heterocycle Synthesis via Azide-Alkyne Cycloaddition

The main goal of this article is to discuss the expansion of click chemistry. A new catalyst composed of CuO nanoparticles embedded in Zn-MOF with the ligand 2,4,6-tris(4-carboxyphenoxy)-1,3,5-triazine (H3L) is presented. The incorporation of CuO nanoparticles into the Zn-MOF structure led to desirable morphology and catalytic properties. The designed catalyst was evaluated for its catalytic role in the multicomponent reaction and copper-catalyzed azide-alkyne cycloaddition (CuAAC) for preparation of triazole rings with 80-91% yield. The catalyst demonstrated an appealing architecture and exhibited robustness, high efficiency, and environmental friendliness. Characterization of the catalyst was performed using various techniques, including Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopes (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), elemental mapping, and X-ray diffraction (XRD). The results suggest that this novel catalyst has the potential to be a valuable tool in the development of new synthetic approaches for a wide range of applications.

Three-pole wheel paddle luminescent metal organic frameworks (LMOFs) based on the oxygen substituted triazine tricarboxylic acid ligand: recognition and detection of small drug molecules and aromatic amine molecules

Luminescent metal organic frameworks (LMOFs) are considered to be a type of promising optical sensing material due to their designable and tunable functions, and stable pore structures. Therefore, the preparation of LMOFs has become a research hotspot in recent years. As we know, triazine carboxylic acid ligands are conducive for constructing LMOF materials due to their large π electron conjugated system. In this work, two crystalline materials [Cd₃(TCPT)₂]·0.5DMF·4H₂O (1) and (H₃O)[Zn₂(TCPT)(μ₂-OH)₂]·0.5DMF·3H₂O (2) were obtained by the reaction of the triazine carboxylic acid ligand 2,4,6-tris(4-carboxyphenoxy)-1,3,5-triazine (H₃TCPT), as an extended carboxylate arm, and d¹⁰ transition metal salts. Their structures were determined by single crystal X-ray diffraction and characterized by infrared spectroscopy (IR), ultraviolet visible spectroscopy (UV-vis), fluorescence spectroscopy, powder X-ray diffraction (PXRD) and thermogravimetric analysis (TG). The experimental results showed that complexes 1 and 2 show excellent fluorescent emission behavior. Thus, we explored their fluorescence sensing properties. To our delight, the results showed that they both had the ability to sense small organic drug molecules and aromatic amine molecules containing o-phenylenediamine (OPD), m-phenylenediamine (MPD) and p-phenylenediamine (PPD). In general, the practical applications of a MOF material are usually limited because of the relatively harsh synthesis methods. In this aspect, we studied the synthesis method in detail to obtain the optimal reaction conditions for the large-scale synthesis of 1 and 2. The preparation of the two LMOF materials only required about 3 hours of heating time and they could be prepared on a large scale, which is significant for the practical applications of LMOFs.

Highly Stable Zinc-Based Metal-Organic Frameworks and Corresponding Flexible Composites for Removal and Detection of Antibiotics in Water

Antibiotic contamination of water bodies is a major environmental concern. Exposure to superfluous antibiotics is an ecological stressor correlated to the development of antibiotic resistance. Thus, it is imperative that effective methods are developed to simultaneously detect and remove such antibiotics so as to avoid inadvertent release. Herein, two flexible three-dimensional (3D) zinc-based metal-organic frameworks (MOFs) {[Zn₂(bcob)(OH)(H₂O)]·DMA}_n (ROD-Zn1) and {[Zn(Hbcob)]·(solvent)}_n (ROD-Zn2) (H₃bcob = 1,3-bis((4'-carboxylbenzyl)oxy)benzoic acid) with rod second building units (SBUs) are successfully prepared. Their exceptional water and chemical stabilities (toward both acid and base), fast sorption kinetics, and unique framework endow the MOFs with excellent uptake capacity toward various antibiotics in the aqueous environment. The adsorption performance was further optimized by one-pot preparation of MOF-melamine foam (MF) hybrid composites, resulting in a hierarchical microporous-macroporous MOF@MF system (ROD-Zn1@MF and ROD-Zn2@MF), which are readily recyclable after adsorptive capture. The mechanisms of adsorption have been deeply investigated by static and competitive adsorption experiments. In addition, the MOFs exhibit excellent fluorescent properties and quenched by trace amounts of antibiotics in water solution. Therefore, ROD-Zn1 and ROD-Zn2 present a dual-functional performance, being promising candidates for detection and removal of antibiotics.

Combining unsaturated metal sites and narrow pores within a Co(ii)-based MOF towards CO2 separation and transformation

Combining unsaturated metal sites and narrow pores within one framework, a unique Co^II-MOF have been prepared, which reveals excellent selective CO₂ uptake over N₂ and CH₄, and good performances in catalytic CO₂ conversion to cyclic carbonates.

Solvatochromism and Selective Sorption of Volatile Organic Solvents in Pyridylbenzoate Metal-Organic Frameworks

Using cobalt(II) as a metal centre with different solvent systems afforded the crystallization of isomorphous metal-organic frameworks {[Co(34pba)(44pba)]·DMF}n (1) and {[Co(34pba)(44pba)]·(C3H6O)}n (2) from mixed 4-(4-pyridyl)benzoate (44pba) and 3-(4-pyridyl)benzoate (34pba) ligands. Zinc(II) under the same reaction conditions that led to the formation of 1 formed an isostructural {[Zn(34pba)(44pba)]·DMF}n framework (3). Crystal structures of all three MOFs were elucidated and their thermal stabilities were determined. The frameworks of 1, 2, and 3 were activated under vacuum to form the desolvated forms 1d, 2d, and 3d, respectively. PXRD results showed that 1d and 2d were identical, consequently, 1d and 3d were then investigated for sorption of volatile organic compounds (VOCs) containing either chloro or amine moieties. Thermogravimetric analysis (TGA) and nuclear magnetic resonance (NMR) were used to determine the sorption capacity and selectivity for the VOCs. Some sorption products of 1d with amines became amorphous, but the crystalline framework could be recovered on desorption of the amines. Investigation of the sorption of water (H2O) and ammonia (NH3) in 1d gave rise to new phases identifiable by means of a colour change (solvatochromism). The kinetics of desorption of DMF, water and ammonia from frameworks 1d and 3d were studied using non-isothermal TGA. Activation energies for both cobalt(II) and zinc(II) frameworks are in the order NH3 < H2O < DMF, with values for the 1d analogue always higher than those for 3d.

Coordinative Reduction of Metal Nodes Enhances the Hydrolytic Stability of a Paddlewheel Metal-Organic Framework

Enhancement of hydrolytic stability of metal-organic frameworks (MOFs) is a challenging issue in MOF chemistry because most MOFs have shown limitations in their applications under a humid environment. Meanwhile, inner sphere electron transfer has constituted one of the most intensively studied subjects in contemporary chemistry. In this report, we show, for the first time, a new conceptual coordinative reduction of Cu²⁺ ion, which is realized in a paddlewheel MOF, HKUST-1, with a postsynthetic manner via inner sphere "single" electron transfer from hydroquinone (H₂Q) to Cu²⁺ through its coordination bond. H₂Q treatment of HKUST-1 under anhydrous conditions leads to the single charge (1+) reduction of approximately 30% of Cu²⁺ ions. Thus, this coordinative reduction is an excellent reduction process to be self-controlled in both oxidation state and quantity. As described below, once Cu²⁺ ions are reduced to Cu⁺, the reduction reaction does not proceed further, in terms of their oxidation state as well as their amount. Also, we demonstrate that a half of the Cu⁺ ions (about 15%) remains in paddlewheel framework with pseudo square planar geometry and the other half of the Cu⁺ ions (about 15%) forms [Cu(MeCN)₄]⁺ complex in a small cage in the fashion of a ship-in-a-bottle after dissociation from the framework. Furthermore, we show that the coordinative reduction results in substantial enhancement of the hydrolytic stability of HKUST-1 to the extent that its structure remains intact even after exposure to humid air for two years.

A thermally stable three-dimensional cobalt(II) coordination polymer based on the V-shaped ligand 4-(4-carboxyphenoxy)isophthalate

A new cobalt(II) coordination polymer (CP), poly[[bis[μ6-4-(4-carboxylatophenoxy)benzene-1,3-dicarboxylato-κ6 O 1:O 1:O 3:O 3′:O 4:O 4′]bis(1,10-phenanthroline-κ2 N,N′)tricobalt(II)] 0.72-hydrate], {[Co3(C15H7O7)2(C12H8N2)2]·0.72H2O} n , (I), is constructed from CoII ions and 4-(4-carboxyphenoxy)isophthalate (cpoia3−) and 1,10-phenanthroline (phen) ligands. Based on centrosymmetric trinuclear [Co3(phen)2(COO)6] secondary building units (SBUs), the structure of (I) is a three-dimensional CP with a (3,6)-connected net and point symbol (42.6)2(44.62.87.102). The positions of four [Co3(phen)2(COO)6] SBUs and four cpoia3− ligands reproduce a Chinese-knot-shaped arrangement along the ab plane. (I) has been characterized by single-crystal X-ray diffraction, IR spectroscopy, powder X-ray diffraction (PXRD) and thermostability analysis. It shows a good thermal stability from room temperature to 673 K. In addition, the temperature dependence of the magnetic properties was measured.

Facile synthesis of ultrafine cobalt oxides embedded into N-doped carbon with superior activity in hydrogenation of 4-nitrophenol

Design and synthesis of low-cost catalysts with high activity and stability for hydrogenation reactions is an important research area of applied catalysis. In this work, we present a kind of ultrafine cobalt oxides encapsulated by N-doped carbon (donated as CoO_x/CN) as efficient catalysts for hydrogenation of 4-nitrophenol (4-NP) process. The CoO_x/CN was fabricated through a pyrolysis strategy using an N-containing metal-organic framework (Co-MOF) as precursor followed by a fine thermal-treatment. With an optimized pyrolysis temperature of 500 °C, the CoO_x species present as ultrafine particles highly dispersed in the obtained catalyst (CoO_x/CN-500). CoO_x/CN-500 exhibits excellent activity and stability in hydrogenation of 4-NP at ambient conditions. The activity is much higher than that of not only bulk cobalt oxides, but also carbon supported CoO_x catalysts. It could be used for more than 8 times without obvious fading in activity. In addition, the concrete role of Co-MOF precursor and pyrolysis condition in the catalyst design was investigated in detail. The interaction between organic ligands and Co ions and the confinement of the crystalline structure of Co-MOF could restrain the aggregation of Co ions during pyrolysis and lead to high dispersion of ultrafine CoO_x species. Meanwhile, the N-containing ligands could be transformed into doped N species (pyridinic and pyrrolic N), endowing the CoO_x species with high electron density and promoting the formation of active sites for the hydrogenation reaction.

Synthesis and proton conductivity of two novel molybdate polymers

Two molybdate polymers H₄[Co(phen)₃]₂[NaO(H₂O)(l-Mo₈O₂₆)]₂·2H₂O (1) and H₂[TEDA][Mo₄O₁₃]·3H₂O (2) were synthesized, proton conductivity of 1 was 3.06 × 10⁻³ S cm⁻¹.

Five transition metal coordination polymers driven by a semirigid trifunctional nicotinic acid ligand: selective adsorption and magnetic properties

Five coordination polymers have been synthesized by a new organic linker containing three distinct types of functional groups together with the mixed 2,2′-bipy or 4,4′-bipy co-ligand, revealing various framework structures and selective gas adsorption and magnetic properties.

A multifunctional MOF as a recyclable catalyst for the fixation of CO2 with aziridines or epoxides and as a luminescent probe of Cr(vi)

A multifunctional metal-organic framework (1) can serve as an efficient and recyclable catalysts for the conversion of CO₂ with aziridines or epoxides. Furthermore, the material can also act as a recyclable luminescent probe for Cr(vi) species among twenty anions.

Structure modulation from unstable to stable MOFs by regulating secondary N-donor ligands

Four new Cd/Zn(ii) MOFs have been synthesized and structurally modulated from unstable to stable by regulating secondary N-donor ligands. Furthermore, YZ-10 shows excellent CO₂ selective uptake over CH₄ and N₂ and uncommon H₂ selective uptake over N₂ at 77 K.

A Sr2+-metal-organic framework with high chemical stability: synthesis, crystal structure and photoluminescence property

Metal-organic frameworks (MOFs) are typically built by assembly of metal centres and organic linkers, and have emerged as promising crystalline materials in a variety of fields. However, the stability of MOFs is a key limitation for their practical applications. Herein, we report a novel Sr 2+: -MOF [Sr₄(Tdada)₂(H₂O)₃(DMF)₂] (denoted as NKU- 105: , NKU = Nankai University; H₄Tdada = 5,5'-((thiophene-2,5-dicar bonyl)bis(azanediyl))diisophthalic acid; DMF = N,N-dimethylformamide) featuring an open square channel of about 6 Å along the c-axis. Notably, NKU- 105: exhibits much outstanding chemical stability against common organic solvents, boiling water, acids and bases, relative to most MOF materials. Furthermore, NKU- 105: is an environment-friendly luminescent material with a bright cyan emission.This article is part of the themed issue 'Coordination polymers and metal-organic frameworks: materials by design'.

A new layer-stacked porous framework showing sorption selectivity for CO2 and luminescence

Luminescent Zn-MOF based stacked layers were assembled, featuring multiple CO₂-binding sites and selective CO₂ adsorption over CH₄.

Light-triggered Supramolecular Isomerism in a Self-catenated Zn(II)-organic Framework: Dynamic Photo-switching CO2 Uptake and Detection of Nitroaromatics

A self-catenated Zn(II)-organic framework formulated as [Zn₂(3,3′-bpeab)(oba)₂]·DMF (1) exhibiting a six-connected 4⁴·6¹⁰·8 topology has been successfully synthesized through the mixed-ligand of kinked 3,3′-bis[2-(4-pyridyl)ethenyl]azobenzene (3,3′-bpeab) and 4,4′-oxybis-benzoic acid (H₂oba) under solvothermal condition. UV light triggers isomerization of complex 1 in a single-crystal-to-single-crystal (SCSC) manner, giving rise to a conformational supramolecular isomer 1_UV through the pedal motion of photoresponsive double bonds. Dynamic photo-switching in the obtained light-responsive supramolecular isomers leads to instantly reversible CO₂ uptake. Furthermore, the ligand originated fluorescence emission of water-resistant complex 1 is selectively sensitive to 4-nitrotoluene (4-NT) owing to a higher quenching efficiency of the perilous explosive over other structurally similar nitroaromatics, prefiguring the potentials of 1 as a fluorescence sensor towards 4-NT in aquatic media.

Crystal structure of poly[diacetato(μ2-1,4-bis(1H-imidazol-1-yl)benzene-κ 2 N:N′)nickel(II)], C26H22N8NiO4

C26H22N8NiO4, monoclinic, P21/c (no. 14), a = 7.520(5) Å, b = 11.662(7) Å, c = 13.666(9) Å, β = 98.519(8)°, V = 1185.3(13) Å3, Z = 2, R gt (F) = 0.0345, wR ref (F 2 ) = 0.1007, T = 293 K.

A lead-porphyrin metal-organic framework: gas adsorption properties and electrocatalytic activity for water oxidation

A 3D non-interpenetrating porous metal-organic framework [Pb2(H2TCPP)]·4DMF·H2O (Pb-TCPP) (H6TCPP = 5,10,15,20-tetra(carboxyphenyl)porphyrin) was synthesized by employment of a robust porphyrin ligand. Pb-TCPP exhibits a one-dimensional channel possessing fairly good capability of gas sorption for N2, H2, Ar, and CO2 gases, and also features selectivity for CO2 over CH4 at 298 K. Furthermore, Pb-TCPP shows electrocatalytic activity for water oxidation in alkaline solution. It is the first 3D porous Pb-MOF that exhibits both gas adsorption properties and electrocatalytic activity for an oxygen evolution reaction (OER).

A highly stable amino-coordinated MOF for unprecedented block off N2 adsorption and extraordinary CO2/N2 separation

ZJU-198 for high CO₂/N₂ separation and low isosteric heat.

Iron-based metal–organic framework, Fe(BTC): an effective dual-functional catalyst for oxidative cyclization of bisnaphthols and tandem synthesis of quinazolin-4(3H)-ones

Fe(BTC) catalyzed synthesis of spirodienones and quinazolin-4(3H)-ones.