Metal-organic Polymers Research Articles

Cover Image, Volume 139, Issue 43

The cover image by Dr. Noorullah Baig shows how metal-organic copolymers containing iron(II) clathrochelated with various arylamines were synthesized via a palladium-catalyzed Sonogashira crosscoupling reaction. The copolymers reveal ultrafast dye adsorption efficiencies up to 100% and exhibit maximum adsorption capacity (qm) for Methylene Blue and Congo Red of 146.63 mg g−1 and 787.40 mg g−1, respectively. The metal-organic polymers demonstrate several advantages, namely, their versatile synthesis, low cost, superior thermal stability, excellent adsorption capacity, and high surface area, which qualify them as prominent adsorbents for water purification applications. DOI: 10.1002/app.52966

Extremely Stable Sulfuric Acid Covalent Organic Framework for Highly Effective Ammonia Capture†

Comprehensive SummaryAmmonia (NH3) is one of the most important industrial feedstocks in the fields of fertilizers, drugs, explosives, ordnance, commercial cleanings, and so on. However, the features of ammonia such as high toxicity and corrosivity, and difficulty in handling would inevitably increase the risk of environmental damage and the deterioration of natural/public lands. Although sorts of solid adsorbents such as metal oxides, zeolites, organic polymers, activated carbons, and metal organic frameworks have been applied in NH3 capture, they still show low uptake capacity, low affinities, and instability. Herein, we developed the first case of a highly stable sulfuric acid covalent organic framework (COF), namely TpBD‐(SO3H)2, as NH3 capturer, in which sulfonic acid sites can strongly interact with NH3 molecules, and enhance the performance of NH3 sorption. As a result, TpBD‐(SO3H)2 shows high chemical stability under strong acid and water conditions, an important merit for the potential application in harsh environment. And it also exhibits high ammonia capacity of 11.5 mmol·g−1 at 298 K and 1.0 bar, making it one of the best in all chemically stable NH3 adsorbents up to date. This work thus develops sulfuric acid COF materials as a new platform for ammonia capture and storage.

Concomitant dimorphism in poly[di-μ-azido-(5,5'-dimethyl-2,2'-bipyridine)iron(II)

The title metal-organic polymer, catena-poly[[(5,5'-dimethyl-2,2'-bipyridine-κ2N,N')iron(II)]-di-μ-azido-κ2N1:N3-[(5,5'-dimethyl-2,2'-bipyridine-κ2N,N')iron(II)]-di-μ-azido-κ2N1:N1], [Fe(N3)2(C12H12N2)]n, features alternating μ-1,1 (end-on mode of coordination) and μ-1,3 (end-to-end mode of coordination) double azide bridges, forming chains running in the [100] direction. The octahedral coordination geometry around the FeII centre is completed by a bidentate 5,5'-dimethyl-2,2'-bipyridine ligand. Two polymorphs for this compound were obtained from the crude reaction product, the first in the space group P-1 and the other in P21/c. The molecular and crystal structures are very similar for both forms, the main difference being that the eight-membered Fe(μ-1,3-N3)2Fe metallacycle formed with end-to-end azide ligands has a nearly flat conformation in the triclinic form and a chair conformation in the monoclinic form. In spite of this geometric difference, both forms have the same density, the same packing index and similar arrangements of the one-dimensional chains in the crystal. As a consequence, they also share very similar Hirshfeld surfaces and fingerprint plots. However, a density functional theory (DFT) computational study showed that the monoclinic form is more stable than the triclinic form by ca 30.5 kJ mol-1.

Back Cover: Chromophore‐Inspired Design of Pyridinium‐Based Metal–Organic Polymers for Dual Photoredox Catalysis (Angew. Chem. Int. Ed. 37/2022)

A universal dual photoredox catalysis platform based on metal–organic polymers synergistically constructed with triphenylpyrylium mimic ligands and reductive metal ions is reported by Yunhe Jin, Chunying Duan et al. in their Research Article (DOI: 10.1002/anie.202204918). This novel strategy enables integration of photoinduced electron transfer and ligand-to-metal charge transfer events, and spatial and kinetic confinement effects of structurally confined pores for enhanced efficiency in photocatalysis of various organic couplings and molecular oxygen activation.

Rücktitelbild: Chromophore‐Inspired Design of Pyridinium‐Based Metal–Organic Polymers for Dual Photoredox Catalysis (Angew. Chem. 37/2022)

Rücktitelbild: Chromophore‐Inspired Design of Pyridinium‐Based Metal–Organic Polymers for Dual Photoredox Catalysis (Angew. Chem. 37/2022)

Chromophore‐Inspired Design of Pyridinium‐Based Metal–Organic Polymers for Dual Photoredox Catalysis

Abstract2,4,6‐Triphenylpyrylium (TPT+) functions as a classic organic photocatalyst and exhibits a noteworthy absorption in the visible range, strongly oxidizing excited states, and a somewhat unstable structure. Inspired by the nuclear chromophore and dual catalysis strategy, herein, we report a universal photoredox platform constructed byTPT+‐mimic bridging ligands and reductive metal ions on the basis of metal–organic supramolecular systems for various organic couplings and molecular oxygen activation under visible‐light irradiation. Significant photoinduced electron transfer and ligand‐to‐metal charge‐transfer events are both integrated and regulated by the spatial and kinetic confinement effects of the structurally confined microenvironments, effectively improving the efficiency of electron transfer and radical–radical coupling processes in photocatalysis. This package deal provides a promising way for the design of novel photocatalysts and the development of versatile and sustainable synthetic chemistry.

Chromophore-Inspired Design of Pyridinium-Based Metal-Organic Polymers for Dual Photoredox Catalysis.

2,4,6-Triphenylpyrylium (TPT+ ) functions as a classic organic photocatalyst and exhibits a noteworthy absorption in the visible range, strongly oxidizing excited states, and a somewhat unstable structure. Inspired by the nuclear chromophore and dual catalysis strategy, herein, we report a universal photoredox platform constructed by TPT+ -mimic bridging ligands and reductive metal ions on the basis of metal-organic supramolecular systems for various organic couplings and molecular oxygen activation under visible-light irradiation. Significant photoinduced electron transfer and ligand-to-metal charge-transfer events are both integrated and regulated by the spatial and kinetic confinement effects of the structurally confined microenvironments, effectively improving the efficiency of electron transfer and radical-radical coupling processes in photocatalysis. This package deal provides a promising way for the design of novel photocatalysts and the development of versatile and sustainable synthetic chemistry.

Chemical CeO2-Based Buffer Layers for Fe(Se,Te) Films

Among other Fe-based superconductors, Fe(Se,Te) is particularly interesting because of the low structural anisotropy, large upper critical fields, low field dependence of the critical current density and low toxicity. It can also be grown as an epitaxial film on a metallic oriented substrate, making the fabrication of a Fe-based coated conductor (CC) possible. Less strict requirements on the template microstructure allow for the design of a simplified design compared to REBCO CCs. This design requires a buffer layer to promote the oriented growth of the superconducting film and avoid diffusion from the metallic template. In this work, CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> based buffer layers are prepared on single crystals via two chemical deposition techniques, metal organic decomposition (MOD) and polymer assisted deposition (PAD). With the design of a suitable thermal treatment, it is possible to obtain oriented buffers with large flat grains and low values of surface roughness. Fe(Se,Te) films are deposited on these templates via laser deposition, and excellent samples are obtained when a Fe(Se,Te) seed layer is used to favour chemical matching with the buffer: sharp superconducting transitions around 16 K and critical current densities exceeding 1 MA cm <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">⁻</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 4.2 K in self-field are observed. These results are the demonstration of the feasibility of a Fe-based CC architecture, with all the relative advantages concerning process simplification and cost reduction.

Crystallochemical design of metal–organic polymer CuBTC and activated carbon composite

Crystallochemical design of metal–organic polymer CuBTC and activated carbon composite

An investigation of Cu‐ZrO 2 ‐TiO 2 / CNTs anode material for lithium‐ion batteries

Material Cu-ZrO2-TiO2/CNTs was prepared through the thermal decomposition of metal organic polymer/carbon nanotubes (CNTs) composite [CuxZrmTil(OCH2CH2O)2(m + l) + x]n/CNTs, which was synthesized through the polymerization of ethylene glycol with metal organic compounds titanium tetra-isopropanolate, zirconium tetra-n-butoxide, and copper acetylacetonate in the presence of CNTs. Higher specific capacity and higher rate capability (351 mAh g−1 at 100 mA g−1, 196 mAh g−1 at 2000 mA g−1) were reached. The reasons for the excellent electrochemical performances of the material could be found from the following aspects. In the thermal decomposition process of the metal organic polymer, nano pores were created in the metal oxide phase and at the same time, part of Ti4+ and Cu2+ cations were reduced to Ti3+ ions and metal Cu. The substitution of Ti4+ ions by Ti3+ ions in TiO2 phase could form oxygen vacancies in the bulk of the material. The nano pores and the oxygen vacancies in Cu-ZrO2-TiO2/CNTs could offer large number of diffusion channels for lithium ions and open up more Li+ ion storage positions to receive Li+ ions at high rate. The presences of the oxygen vacancies, the Ti3+ ions, and the metal copper in the material could enhance the electric conductivity of the material. The investigation results show that the presence of Zr4+ ions in the material could stabilize the pore structure. The stable pore structure, the oxygen vacancies, and the good electric conductivity of the material render a highly efficient anode material for Li+ batteries. A cycling life-time test shows that the Cu-ZrO2-TiO2/CNTs anode material gives a specific capacity of 351 mA h g−1 at 100 mA g−1 and a capacity retention rate of 92% after 200 cycles of charge/discharge.

Cu-MOF@PVP/PVDF hybrid composites as tunable proton-conducting materials

Proton exchange membrane (PEM) is one of the core materials which were widely used in the field of fuel cells (FCs). In recent years, the metal organic frameworks (MOFs) and polymer composite membranes as tunable proton-conducting materials have showed great potential in this field. Herein, a Cu(II)-based metal organic framework (Cu-MOF) with acid/base stability was introduced into poly(vinylpyrrolidone)/poly(vinylidene fluoride) (PVP/PVDF, PP) to fabricate hybrid membranes(Cu-MOF@PP-X, where X is the % Cu-MOF content). The effects of Cu-MOF loading amounts on the conductive behavior of Cu-MOF@PP-X composites have been documented. It is worth noting that Cu-MOF@PP-50 exhibited the proton conductivity up to 4.36 ​× ​10−4 ​S ​cm−1 at 353 ​K and 98% relative humidity (RH). In addition, the value of proton conduction is about two orders of magnitude higher than that of the parent Cu-MOF (1.91 ​× ​10−6 ​S ​cm−1). This work contributes to driving further advances of MOF/polymer composites in proton-conducting apparatus.

Polyimide/ZIFs mixed matrix membranes with tunable interfacial interaction for efficient gas separation

Manipulating favorable interfacial microstructure is crucial to rationally design a high-performance mixed matrix membrane with defect-free interface. We describe herein an efficient pathway to finely tune the interfacial adhesion through balancing the metal organic frameworks and polymer functionality. The varied number of hydrogen bonds are established involving the CHO groups in hybrid ZIF-8-90(x) fillers with varied carboxaldehyde-2-imidazole linker contents and 6FDA-DAM:DABA copolyimides having adjustable COOH groups concentrations, thereby precisely controlling the membrane interfacial bonding behavior. As expected, the gas selectivity of the resulting membranes is gradually enhanced with increasing carboxaldehyde-2-imidazole linker substitution ratio in ZIF-8-90(x), mainly contributed by significant improvements in hydrogen bonding strength. The enhanced interaction is confirmed by good adhesion visualized in SEM images and the C O vibration band shift in FTIR spectra. Meanwhile, adjusting the proportion of DABA moiety in polymers is an auxiliary path to regulate the interfacial bonding strength. The optimized membrane of 6FDA-DAM:DABA (1:1)/10 wt.% ZIF-8-90(30) has enhanced H 2 /CH 4 and CO 2 /CH 4 ideal selectivities of 75.4 and 43.6, respectively, with H 2 and CO 2 permeabilities of 222 Barrer and 128 Barrer. These findings imply that progressively regulating filler and polyimide functionality is a feasible route to finely tailor interfacial hydrogen bonding strength to achieve a membrane with tunable separation performance. • Finely tune the interfacial adhesion through balancing the ZIFs and polymer functionality. • Adjusting the content of CHO-IM linker and DABA moiety can gradually regulate interfacial hydrogen bonding strength. • 6FDA-DAM:DABA (1:1)/10%ZIF-8-90 (30) film with optimum polymer-fillers interaction showing maximum gas selectivity.

Synthesis of three imidazole derivatives and corrosion inhibition performance for copper

Three imidazole derivatives, including 3-(4-(2,4-dichlorophenyl)-5-methyl-1H-imidazol-2-yl)pyridine (PDI), 2-(4-(2,4-dichlorophenyl)-5-methyl-1H-imidazol-2-yl)pyrazine (PAI) and 2-(4-(2,4-dichlorophenyl)-5-methyl-1H-imidazol-2-yl)pyrimidine (PMI), were synthesized. The structure of these compounds was confirmed by LC-MS, 1H NMR, 13C NMR and FTIR spectra. The inhibition performance in 3.5 wt% NaCl was investigated by electrochemical measurement and surface analysis. Results show that the corrosion efficiency of PDI (95.93%) was higher than PAI (69.61%) and PMI (20.46%), which is consistent with the adsorption energy calculated by molecular dynamics simulation. The corrosion inhibition mechanism could be explained by the metal–organic polymer film formed on the copper surface: on the one hand, the π-system formed by aromatic rings is tightly adsorbed on the copper substrates; on the other hand, the nitrogen atoms in the imidazole ring are coordinated with the metal ions in solution to form metal–organic polymer which could improve the compactness of the hydrophobic film.

Design of Metal-Organic Polymers MIL-53(M3+): Preparation and Characterization of MIL-53(Fe) and Graphene Oxide Composite

This article presents a crystal chemical analysis, generalization, and systematization of structural characteristics of metal-organic polymers MIL-53(M3+) with M = Al, Cr, Ga, and Fe. The division of the MIL-53(M3+) structures into a morphotropic series was performed, which made it possible to predict the formation of new compounds or solid solutions with the corresponding composition and structure. The change in the symmetry of MIL-53(M3+) and the causes of polymorphs formation are explained on the basis of crystal chemical rules. The efficiency of the revealed regularities in the structural characteristics of the MIL-53(M3+) phases were experimentally confirmed for MIL-53(Fe) and composite MIL-53(Fe)/GO (GO-graphene oxide) by several methods (powder X-ray, X-ray absorption, and photoelectron spectroscopy). For the first time, different coordination numbers (CN) (CNFe = 4.9 for MIL-53(Fe)—two types of coordination polyhedra with CNFe = 6 and CNFe = 4; CNFe = 4 for MIL-53 (Fe3+)/GO) and the formal charges (FC) of iron ions (variable FC of Fe (2+δ)+ in MIL-53(Fe3+) and Fe2+ in MIL-53(Fe3+)/GO) were found. These experimental data explain the higher photocatalytic activity of MIL-53(Fe3+)/GO in photo-Fenton reactions—RR195 decomposition.

Synthesis and Characterization of Metal-Organic Polymer based on Fe(III)

In this work, a coordination polymer based on iron trinuclear acetate was synthesized. The coordination polymer was obtained in two stages. At the first stage [Fe3O(CH3CO2)6(H2O)3]·2H2O – tricyclic iron acetate was synthesized. As the dicarboxylate ligand, we chose muconic acid, which is not toxic to the body. Double bonds in its structure create additional nodes for interaction with drugs. The optimal conditions for the synthesis of a coordination polymer based on tricyclic iron acetate and muconic acid were selected: solvothermal synthesis at 78 °C, autogenous pressure and using ethanol as a solvent. The resulting coordination polymer is a nanosized mesoporous framework with a narrow pore distribution, an average radius of~1.18 nm, and a developed specific surface area of 512.1 m2/g. The composition and crystal structure of tricyclic iron acetate and a coordination polymer based on it have been confirmed by the methods of elemental and X-ray phase analysis.

Investigation of Adsorption Capacity of Metal-Organic Polymers

In this work, we studied a biocompatible hybrid material based on iron (III) and muconic acid oxoclusters. It has been shown that coordination polymers are a promising class as functional materials for various purposes (as sorbents, catalysts, conductors, storage materials, etc.). The adsorption capacity of the obtained adsorbent for removing dyes from the prepared solution was in the following order: CR&gt; MB&gt; MV. From the results of the study, we can conclude that the dye Congo red is best suited for adsorption by the coordination polymer. The maximum absorption of the dye on organometallic coordination polymers occurs in the pH range 5 - 7 with adsorption of ~ 90%, which is important for the potential practical application of such coordination polymers as carriers for drug delivery.

Investigation of Physical Properties of Fe(III) Containing Metal-Organic Polymers

In this work, we studied the properties of a specially synthesized organometallic coordination polymer - a porous coordination polymer with biocompatible structural elements based on oxoclusters of iron muconate (III). The samples were investigated by scanning electron microscopy, thermogravimetric analysis combined with differential scanning calorimetry, and the study of low-temperature nitrogen adsorption of a sample obtained by a modified solvothermal technique. It is shown that most of the pores of the sample have an average radius of 18,8 Å ~ 1,88 nm. Also, as a result of the study, it is necessary to conclude that the synthesized material has a developed surface area - it is 512,1 m2/g and the pore volume is ~ 0,48 cm3/g. It should be concluded that such materials are promising as components for a new generation of various kinds of functional materials with improved or unique characteristics. It is obvious that further research in this area is important from both fundamental and applied points of view.

On-Surface Synthesis of Ligands to Elaborate Coordination Polymers on an Au(111) Surface.

On-surface metal-organic polymers have emerged as a class of promising 2D materials. Here, we propose a new strategy to obtain coordination polymers by transforming supramolecular networks into coordination polymers by surface-assisted cyclo-dehydrogenation of organic building blocks. All nanostructures are fully characterized by using scanning tunneling microscopy under ultra-high vacuum on a gold surface. We demonstrated that the balance between molecule-molecule interaction and molecule-substrate interaction can be drastically modified by a strong modification of the geometry of the molecules thanks to a thermal annealing. This new way is an efficient method to elaborate on-surface coordination polymers.

Coordination Complexes as a New Generation Photosensitizer for Photodynamic Anticancer Therapy.

Photodynamic therapy (PDT) has become an alternative to standard cancer treatment methods such as surgery, chemotherapy and radiotherapy. The uniqueness of this method relies on the possibility of using various photosensitizers (PS) that absorb and convert light emission in radical oxygen-derived species (ROS). They can be present alone or in the presence of other compounds such as metal organic frameworks (MOFs), non-tubules or polymers. The interaction between DNA and metal-based complexes plays a key role in the development of new anti-cancer drugs. The use of coordination compounds in PDT has a significant impact on the amount ROS generated, quantum emission efficiency (Φem) and phototoxic index (PI). In this review, we will attempt to systematically review the recent literature and analyze the coordination complexes used as PS in PDT. Finally, we compared the anticancer activities of individual coordination complexes and discuss future perspectives. So far, only a few articles link so many transition metal ion coordination complexes of varying degrees of oxidation, which is why this review is needed by the scientific community to further expand this field worldwide. Additionally, it serves as a convenient collection of important, up-to-date information.

Imine‐Induced Metal‐Organic and Covalent Organic Coexisting Framework with Superior Li‐Storage Properties and Activation Mechanism

Due to the adjustable structure and the broad application prospects in energy and other fields, the exploration of porous organic materials [metal-organic polymers (MOPs), covalent organic frameworks (COFs), etc.] has attracted extensive attention. In this work, an imine-induced metal-organic and covalent organic coexisting framework (Co-MOP@COF) hybrid was designed based on the combination between the amino units from the organic ligands of Co-MOP and the aldehyde groups from COF. The obtained Co-MOP@COF hybrid with layer-decorated microsphere morphology exhibited good electrochemical cycling performance (a large reversible capacity of 1020 mAh g-1 after 150 cycles at 100 mA g-1 and a reversible capacity of 396 mAh g-1 at 500 mA g-1 ) as the anode for Li-ion batteries. The coexisting framework structure endowed the Co-MOP@COF hybrid with more surface area exposed in the exfoliated COF structure, which provided rapid Li-ion diffusion, better electrolyte infiltration, and effective activation of functional groups. Therefore, the Co-MOP@COF hybrid material achieved an enhanced Li storage mechanism involving multi-electron redox reactions, related to the CoII center and organic groups (C=C groups of benzene rings and C=N groups), and furthermore improved electrochemical performance.