Metal-organic Hybrid Research Articles

A ROS reservoir based on a polyoxometalate and metal-organic framework hybrid for efficient bacteria eradication and wound healing

Infections by bacteria always post significant challenges to global human health. Recent developed non-antibiotic treatment, such as using metal–organic frameworks (MOFs) to kill bacteria by generating reactive oxygen species (ROS) represents a promising strategy. However, drawbacks including low efficiencies of ROS generation and high concentrations of toxic metal ions released always exist. We have creatively designed a robust polyoxometalate (POM) and MOF hybrid (denoted as CuPOM-MOF@S) that functions as an efficient catalytic reservoir for cascaded generation of ROS (mainly ·OH) from H2O2 thus eradicating bacteria and enhancing wound healing at an administration dosage as low as 5 μg∙mL−1. The remarkable antibacterial capability surpasses those for most MOF-based materials reported thus far, which is mainly attributed to the reservation of massive catalytic copper ions, the synergistic effect regarding catalytic activity between MOFs and Keggin-type POMs as well as its bacteria-capturing ability by the coated surfactants. Its biological safety is investigated and confirmed by cell cytotoxicity and body weight assessment. This work presents a prospective strategy towards cascaded ROS generation by combining inorganic catalytic POMs with MOFs thus for multiple biomedical applications including treating bacterial infections and cancer as well as inducing biological signal responses.

Role of Transition Metals in Metal-Organic Frameworks as Nanoporous Ion Emitters for Thermal Ionization Mass Spectrometry.

Thermal ionization mass spectrometry is a powerful analytical technique that allows for precise determination of isotopic ratios. Analysis of low abundance samples, however, can be limited by the ionization efficiency. Following an investigation into a new type of metal-organic hybrid material, nanoporous ion emitters (nano-PIEs), devised to promote the emission of analyte ions and reduce traditional sample loading challenges, this work evaluates the impact that changing the metal in the material has on the ionization of uranium (U). Being derived from metal-organic frameworks (MOFs), nano-PIEs inherit the tunability of their parent MOFs. The MOF-74 series has been well studied for probing the impact various framework metals (i.e., Mg, Mn, Co, Ni, Cu, Zn, and Cd) have on material properties, and thus, a series of nano-PIEs with different metals were derived from this isoreticular MOF series. Trends in ionization efficiency were studied as a function of ionization potential, volatility, and work function of the framework metals to gain a better understanding of the mechanism of analyte ionization. This study finds a correlation between the analyte ionization efficiency and nano-PIE framework metal volatility that is attributed to its tunable thermal stability and degradation behavior.

Peptide nucleic acid-zirconium coordination nanoparticles

Ideal drug carriers feature a high loading capacity to minimize the exposure of patients with excessive, inactive carrier materials. The highest imaginable loading capacity could be achieved by nanocarriers, which are assembled from the therapeutic cargo molecules themselves. Here, we describe peptide nucleic acid (PNA)-based zirconium (Zr) coordination nanoparticles which exhibit very high PNA loading of >,94% w/w. This metal-organic hybrid nanomaterial class extends the enormous compound space of coordination polymers towards bioactive oligonucleotide linkers. The architecture of single- or double-stranded PNAs was systematically varied to identify design criteria for the coordination driven self-assembly with Zr(IV) nodes at room temperature. Aromatic carboxylic acid functions, serving as Lewis bases, and a two-step synthesis process with preformation of Zr_{6} O_{4} (OH)_{4} turned out to be decisive for successful nanoparticle assembly. Confocal laser scanning microscopy confirmed that the PNA-Zr nanoparticles are readily internalized by cells. PNA-Zr nanoparticles, coated with a cationic lipopeptide, successfully delivered an antisense PNA sequence for splicing correction of the beta-globin intron mutation IVS2-705 into a functional reporter cell line and mediated splice-switching via interaction with the endogenous mRNA splicing machinery. The presented PNA-Zr nanoparticles represent a bioactive platform with high design flexibility and extraordinary PNA loading capacity, where the nucleic acid constitutes an integral part of the material, instead of being loaded into passive delivery systems.

Metal-organic Zn-zoledronic acid and 1-hydroxyethylidene-1,1-diphosphonic acid nanostick-mediated zinc phosphate hybrid coating on biodegradable Zn for osteoporotic fracture healing implants.

Zn and its alloys are increasingly under consideration for biodegradable bone fracture fixation implants owing to their attractive biodegradability and mechanical properties. However, their clinical application is a challenge for osteoporotic bone fracture healing, due to their uneven degradation mode, burst release of zinc ions, and insufficient osteo-promotion and osteo-resorption regulating properties. In this study, a type of Zn2+ coordinated zoledronic acid (ZA) and 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) metal-organic hybrid nanostick was synthesized, which was further mixed into zinc phosphate (ZnP) solution to mediate the deposition and growth of ZnP to form a well-integrated micro-patterned metal-organic/inorganic hybrid coating on Zn. The coating protected noticeably the Zn substrate from corrosion, in particular reducing its localized occurrence as well as suppressing its Zn2+ release. Moreover, the modified Zn was osteo-compatible and osteo-promotive and, more important, performed osteogenesis in vitro and in vivo of well-balanced pro-osteoblast and anti-osteoclast responses. Such favorable functionalities are related to the nature of its bioactive components, especially the bio-functional ZA and the Zn ions it contains, as well as its unique micro- and nano-scale structure. This strategy provides not only a new avenue for surface modification of biodegradable metals but also sheds light on advanced biomaterials for osteoporotic fracture and other applications. STATEMENT OF SIGNIFICANCE: Developing appropriate biodegradable metallic materials is of clinical relevance for osteoporosis fracture healing, whereas current strategies are short of good balance between the bone formation and resorption. Here, we designed a micropatterned metal-organic nanostickmediated zinc phosphate hybrid coating modified Zn biodegradable metal to fulfill such a balanced osteogenicity. The in vitro assays verified the coated Zn demonstrated outstanding pro-osteoblasts and anti-osteoclasts properties and the coated intramedullary nail promoted fracture healing well in an osteoporotic femur fracture rat model. Our strategy may offer not only a new avenue for surface modification of biodegradable metals but also shed light on better understanding of new advanced biomaterials for orthopedic application among others.

High performance Hetero-Shelled hollow structure Metal-Organic framework hybrid material for the efficient electrochemical determination of lead ions

Electrochemical sensing has unique advantages in developing on-site and online detection technologies for heavy metal ions (HMIs) due to its fast response, simple operation, high sensitivity, and portable instruments. The vigorous development of modern micro/nanomaterial preparation technology has provided greater space for improving the performance of electrochemical sensing platforms. In this work, a novel hetero-shelled hollow structure metal–organic framework (MOF) hybrid material (denoted as HCZ@UN) was prepared by adopting the hollow carbonized ZIF-8 (HCZ) as the substrate for growing UiO-66(Zr)–NH2 (UN), and subsequently used for efficient electrochemical detection of lead ions (Pb2+). The grown UN crystal particles were anchored on the HCZ hollow cages and showed nanometer size. The unique shell structure and nanometer size of UN created large specific surface area and rich accessible adsorption sites, which promoted the preconcentration of Pb2+. While the hollow carbon polyhedron structure of HCZ improved the dispersibility of UN and electron transfer ability of the material. These factors synergistically improved the detection sensitivity and sensing performance for Pb2+ determination with a wide linear range of 0.100–500 nM, a low detection limit of 0.0492 ± 0.00523 nM as well as good selectivity, repeatability and long-term stability. This paper provides a simple and effective method for the preparation of electroactive MOF functional materials, which is expected to inspire more interest in building other MOF-based materials with unique structure, high-performance and extensive application value.

The optimization of the adsorption desulfurization process for dibenzothiophene in a model oil using different ratios of hybrid MOF: AC micro adsorbers

Elimination of the release of hazardous sulfur compounds into the environment is imperative, and achieving this requires the desulfurization of petroleum products using an effective method. Adsorption desulfurization is gaining as a cost-effective alternative to various other techniques. In this study, cobalt-based metal-organic framework (Co-MOF) and Hybrid MOF: AC adsorbers were prepared using various ratios through the solvothermal method. The objective was to determine the optimal ratio for maximum removal of dibenzothiophene in a model oil through batch process adsorption. The adsorbers were characterized using FTIR, XRD, FESEM-EDS, and N2 adsorption-desorption analysis. The results indicated that a ratio of 1:5 MOF: AC achieved a 98% removal (147.57 mg/g) of DBT among (MOF, AC, 1:1 MOF: AC, 1:2 MOF: AC, and 1:10 MOF: AC) due to its optimal number of active sites and surface area. Furthermore, the optimal conditions for maximum DBT adsorption were a dosage of 0.1 g and a contact time of 2 h. The kinetic study of the adsorber showed conformity with a pseudo-first-order model.

Synthesis, crystal structure, Hirshfeld surface, and DFT studies of a Copper(II) complex of 5,5′-dimethyl-2,2′-bipyridine and 1,2,2-trimethylcyclopentane-1,3-dicarboxylic acid

A new metal-organic hybrid complex [Cu(5,5′-dmbipy) (D-cam) (H2O)]n (1), (5,5′-dmbipy = 5,5′-dimethyl-2,2′-bipyridine, D-cam = D-camphoric acid anion) was hydrothermally synthesized. This complex was characterized by FTIR spectroscopy, TGA, and single-crystal X-ray diffraction. Crystallographic studies show that the title complex 1 crystallizes in an orthorhombic system with a P212121 space group with a = 06.9518(05) Ǻ, b = 13.5516(13) Ǻ, c = 22.6380(02)Ǻ; V = 2132.7(3) Ǻ3. The title CuII complex adopts a square pyramidal configuration. DFT study and Hirshfeld topology analysis of complex 1 was also done. The crystal achieves its three-dimensional structure and stability through polymeric chains having helical motifs of arrangement in between moieties and interconnected through hydrogen bonding interactions between the apical water molecule and non-coordinated oxygen atoms of the D-cam2- ligands. TGA, DFT calculations and Hirshfeld topology analysis revealed that the title complex 1 was stable.

Bioconjugation in Materials Science

AbstractWith the advent of bioconjugation chemistry in the last two decades, highlighted by the Nobel Prize 2022, the quest for possible novel applications has been greatly intensified, broadening the prospects of these mostly simple, specific, and high‐yield reactions. The advancement of bioconjugation methods is anticipated to expand the scope of bioinstructive and bioadaptive materials science in the future. This perspective article will discuss the reactions developed in this research area over the last 10 years for coupling various biological entities such as polysaccharides, oligonucleotides, peptides, and proteins. Building on this, the impact of bioconjugation reactions in materials science and 3D printing, including their challenges and requirements is shown. Established procedures for modifying molecular structures such as Covalent and Metal Organic Frameworks (COF/MOF) or hybrid materials for biomedical applications and the scope for future research and optimization will be presented.

Titelbild: Guiding Principles for the Rational Design of Hybrid Materials: Use of DFT Methodology for Evaluating Non‐Covalent Interactions in a Uranyl Tetrahalide Model System (Angew. Chem. 33/2023)

Uranyl tetrahalide ions assemble into hybrid material through Non-Covalent Interactions (NCIs) in the presence of organic charge balancing cations. NCIs such as hydrogen bonding serve to stabilize these supramolecular hybrid complexes and act as the fundamental driving force for crystallization. In their Research Article (e202305073), Sara E. Mason, Tori Z. Forbes et al. employed these hybrid complexes as a model system to assess the effect of NCIs on the vibrational properties and formation enthalpies of metal–organic hybrid materials.

Cover Picture: Guiding Principles for the Rational Design of Hybrid Materials: Use of DFT Methodology for Evaluating Non‐Covalent Interactions in a Uranyl Tetrahalide Model System (Angew. Chem. Int. Ed. 33/2023)

Uranyl tetrahalide ions assemble into hybrid material through Non-Covalent Interactions (NCIs) in the presence of organic charge balancing cations. NCIs such as hydrogen bonding serve to stabilize these supramolecular hybrid complexes and act as the fundamental driving force for crystallization. In their Research Article (e202305073), Sara E. Mason, Tori Z. Forbes et al. employed these hybrid complexes as a model system to assess the effect of NCIs on the vibrational properties and formation enthalpies of metal–organic hybrid materials.

Optimized geometric structure of Zn-BTC/POAP and Fe-BTC/POAP systems as electroactive materials in pseudocapacitors

In this work, Fe(II)-based metal organic framework (MOF), Zn-based MOF and hybrid poly orthoaminophenol/MOF composite were synthesized via a chemical method. Synthesized composite films have been characterized by conventional electrochemical methods and computational approach. The computational results show that both Zn-BTC and Fe-BTC interact well with 3POAP. Meanwhile, the adsorption energy of 3POAP on Fe-BTC is 2.03 eV higher than that of Zn-BTC. Therefore, it can be mentioned that the high adsorption energy of conductive polymer POAP on Fe-BTC compared to Zn-BTC has led to its better performance as the electrode of supercapacitors and these findings confirm the electrochemical results. It was found that in Zn-BTC/3POAP and Fe-BTC/3POAP systems the charge is transferred from the 3POAP to the MOFs. The results showed that the charge transfer from 3POAP to Fe-BTC is more than Zn-BTC which is a confirmation of the higher adsorption of 3POAP on Fe-BTC. The 3D periodic structure of Fe-BTC is generated by binuclear Fe(II) paddlewheel building units (PBUs) connected via the 1,3,5-benzenetricarboxylate organic ligands. Also, the adsorption energy of 3POAP on Fe2(PhCOO)4 and Zn2(PhCOO)4 was calculated using supermolecular approach. These results are compatible with the adsorption energy obtained from the periodic calculations, so that the adsorption of Fe structure was more than that of Zn. The Fe2(PhCOO)4…3POAP structure has the lowest band gap energy, so it can be concluded that the better adsorption of 3POAP on Fe-BTC not only results in higher adsorption energy, but also better electrical conductivity than the Zn-BTC. Computational results are in agreement with electrochemical results.

Single-Atom Catalysts and Dual-Atom Catalysts for CO2 Electroreduction: Competition or Cooperation?

Developing highly active and selective electrocatalysts for electrochemical reduction of CO2 can reduce environmental pollution and mitigation of greenhouse gas emission. Owing to maximal atomic utilization, the atomically dispersed catalysts are broadly adopted in CO2 reduction reaction (CO2 RR). Dual-atom catalysts (DACs), with more flexible active sites, distinct electronic structures, and synergetic interatomic interactions compared to single-atom catalysts (SACs), may have great potential to enhance catalytic performance. Nevertheless, most of the existing electrocatalysts have low activity and selectivity due to their high energy barrier. Herein, 15 electrocatalysts are explored with noble metallic (Cu, Ag, and Au) active sites embedded in metal-organic hybrids (MOHs) for high-performance CO2 RR and studied the relationship between SACs and DACs by first-principles calculation. The results indicated that the DACs have excellent electrocatalytic performance, and the moderate interaction between the single- and dual-atomic center can improve catalytic activity in CO2 RR. Four among the 15 catalysts, including (CuAu), (CuCu), Cu(CuCu), and Cu(CuAu) MOHs inherited a capability of suppressing the competitive hydrogen evolution reaction with favorable CO overpotential. This work not only reveals outstanding candidates for MOHs-based dual-atom CO2 RR electrocatalysts but also provides new theoretical insights into rationally designing 2D metallic electrocatalysts.

Adsorption of Phenol from Both Acidic and Basic Industrial Waste via Newly Synthesized Metal Organic Framework Hybrid Smart Adsorbents

Newly prepared pH-responsive metal organic frameworks (MOFs) having a specific surface area of 1400 m2/g could be exploited in the total removal of pollutants from wastewaters in this work. Smart core–shell structures of COP-150@ZIF-8 and NPC@ZIF-8 were successfully synthesized in large scales through internal extended growth under polyvinylpyrrolidone (PVP) regulation and used in phenol removal from aqueous media. The essential factors on the removal, namely pH, initial concentration of phenol, contact time, adsorbent dosage, and temperature, were studied and optimized. The experimental data were investigated by different kinetic and isotherm models, in which the removal of phenol by these smart sorbents is correlated with the Freundlich isotherm model and was found to follow the pseudo-second-order kinetic model. Excellent adsorption capacity of 1670 mg·g–1 and high efficiency were achieved in phenol removal (mixing time of only 20 min) that suggest the application of smart NPC@ZIF-8 core–shell in water filtration. Also, the optimal concentration of smart NPC@ZIF-8 and smart COP@ZIF-8 core–shell adsorbents was obtained as 300 and 250 mg·L–1, respectively. On the other hand, more than 94% removal of phenol was observed at pH = 3 for both smart nanosorbents (mere use of 0.1 g adsorbent). The results of thermodynamics confirm that the process of adsorption is exothermic and spontaneous. Moreover, having simulated the atomistic investigation of phenol removal via molecular dynamics, it was concluded that the different designed adsorbents in this work have a high capacity to remove phenol, specifically NPC@ZIF-8.

Combined hydrogenation of CO2 and CO to methanol using Aerosol-Assisted Metal-Organic Framework-Derived hybrid catalysts

In this study, a spray-drying approach is presented to develop (1) Cu-based metal–organic framework (Cu-MOF) supported on aluminum oxide nanoparticle cluster and (2) its derivedCu-ZnO/Al2O3 hybrid catalyst for combined (CO + CO2) hydrogenation to methanol. The results show superior high space time yield, 23.14 mmol gcat-1h−1, and selectivity to methanol (85%) were achievable under a moderate-pressure (30 bar) and relatively low-temperature (220 °C) operation. Incorporation of ZnO and Al2O3 (i.e., in the form of nanoparticle cluster) enhanced the dispersion and the redox ability of Cu in the MOF-derived catalyst, both of which were critical factors to the catalytic activity toward the combined hydrogenation of CO2 and CO to methanol. An optimal performance, in terms of the methanol yield, was achieved by using the catalyst with a Cu/Zn molar ratio of 2 and partially reduction by H2 at a relatively lower temperature (300 °C). The work demonstrates a new route for the design of MOF-derived catalyst by using an aerosol-assisted synthesis approach, showing promise for the catalysis of a variety of chemical reactions in the field of CO2 capture and utilization.

Supramolecular glasses with color-tunable circularly polarized afterglow through evaporation-induced self-assembly of chiral metal–organic complexes

The fabrication of chiral molecules into macroscopic systems has many valuable applications, especially in the fields of optical displays, data encryption, information storage, and so on. Here, we design and prepare a serious of supramolecular glasses (SGs) based on Zn-L-Histidine complexes, via an evaporation-induced self-assembly (EISA) strategy. Metal-ligand interactions between the zinc(II) ion and chiral L-Histidine endow the SGs with interesting circularly polarized afterglow (CPA). Multicolored CPA emissions from blue to red with dissymmetry factor as high as 9.5 × 10−3 and excited-state lifetime up to 356.7 ms are achieved under ambient conditions. Therefore, this work not only communicates the bulk SGs with wide-tunable afterglow and large circular polarization, but also provides an EISA method for the macroscopic self-assembly of chiral metal–organic hybrids toward photonic applications.

Hg2+ removal from wastewater by anchoring nitrogen/sulfur active center onto metal-organic framework via Schiff-base reaction: Synthesis, characterization, and experiment

Remediation of Hg2+ pollution in wastewater is imminent. Herein, a Metal-Organic Framework hybrid Uio-DBD-x was designed and synthesized via rational introducing the 5-Diamino-1,4-benzenedithiol Dihydrochloride (DBD) molecule onto parent Uio-66-NH2. By optimizing the synthesis conditions, the material exhibited better adsorption performance when x = 1. The characteristics including crystallinity, morphology, and pore size were analyzed. 12.64 nm for pore diameter and 493.73 m2/g for surface areas of Uio-DBD-1 were obtained. Subsequently, the adsorption performance of Uio-DBD-1 towards Hg2+ was studied under different pH, dosage, concentration, and time. The corresponding maximum adsorption capacity of 423.10 mg/g and equilibrium time of 10 min was achieved. Remarkably, Hg2+ concentration could be reduced below the emission limit (0.05 mg/L). Furthermore, the selectivity and reusability of the adsorbent were investigated, and the results manifested that Uio-DBD-1 maintains high removal efficiency (82.10%) after 6 times recycles. The possible adsorption mechanism could be ascribed to the strong interaction (chelation, proton exchange, and coordination) between Hg2+ and –NH2/-SH groups. This work breaks new ground in functional material design and paves the way for wastewater treatment.

A carbon catalyst doped with Co and N derived from the metal-organic framework hybrid (ZIF-8@ZIF-67) for efficient oxygen reduction reaction

A carbon catalyst doped with Co and N derived from the metal-organic framework hybrid (ZIF-8@ZIF-67) for efficient oxygen reduction reaction

Highly Selective On-Surface [2 + 2] Cycloaddition Induced by Hierarchical Metal–Organic Hybrids

On-surface synthesis of phenylenes is a promising strategy to form extended π-conjugated frameworks but normally lacks selectivity in achieving uniform products. Herein we demonstrate that the debromination reaction of 2,3-dibromophenazine (DBPZ) on Au(111) and Ag(111) surfaces can vary significantly considering the involvement of metal-organic hybrids (MOHs). On Au(111), [2 + 2] and [2 + 2 + 2] cycloadditions facilitate instantaneously upon the debromination occurring, while on Ag(111), several MOHs have been observed under sequential thermal annealing, leading to finally the uniform [2 + 2] cycloaddition product exclusively. By means of scanning tunneling microscopy (STM) and bond-resolved atomic force microscopy (BR-AFM), we have unambiguously depicted the chemical structure of related reaction intermediates and unraveled the undocumented role of hierarchical evolution of MOHs in steering the chemical selectivity.

A carbon catalyst doped with Co and N derived from the metal-organic framework hybrid (ZIF-8@ZIF-67) for efficient oxygen reduction reaction

Carbon-based catalysts for the oxygen reduction reaction (ORR) are considered potential substitutes for the expensive platinum-based catalysts. Recently, transition metal and nitrogen co-doped carbon materials (M-N-C) have attracted much attention from researchers due to their low cost and excellent activity. A cobalt- and nitrogen-co-doped porous carbon material (Co-N@CNT-C800) was prepared by the simple one-step pyrolysis of a star fruit-like MOF hybrid (ZIF-8@ZIF-67) at 800 °C. It consisted of CNTs with substantial Co and N co-doping and had a large surface area (428 m2·g−1). It had an excellent half-wave potential and good current density in alkaline media in the ORR with values of 0.841 V and 5.07 mA·cm−2, respectively. Compared with commercial Pt/C materials it also had excellent electrochemical stability and methanol tolerance. This research provides an effective way to fabricate low cost, high activity electrocatalysts for use in energy conversion.

A Novel Molecular Assembly of a Cobalt-Sulfate Coordination Polymer and Melamine: A Manifestation of Magnetic Anisotropy.

A novel molecular assembly of a cobalt-sulfate coordination polymer and melamine is synthesized under acidic conditions. Bar-shaped pink monocrystals as long as 1 mm are found to align along magnetic field lines in the proximity of a strong magnet. Magnetometry shows no hysteresis at temperatures down to 2 K but instead magnetic anisotropy and antiferromagnetic coupling. X-ray diffraction on a single crystal reveals that the cobalt-sulfate chains are along the shortest lattice vector or the crystal's long axis. The crystal alignment along the magnetic flux can be attributed to single-ion anisotropy that results in longitudinal antiferromagnetic coupling along the chain. Both structurally and magnetically isotropic crystals of metal-organic hybrid materials can be highly useful as elemental components in magneto-optics.