A robust zirconium amino acid metal-organic framework for proton conduction

Metal-organic chelator frameworks for arsenic-based cancer treatment

The off-target toxicity of arsenic trioxide chemotherapy is a common Achilleś heel of metallodrugs. This limitation is usually mitigated by employing various cargo agents capable of transporting arsenic species to specific sites. More specifically, two of the most explored strategies to address arsenic trioxide's off-target toxicity include: (i) the complexation of As(III) species with chelating agents and (ii) their immobilization, either on the surface or, within non-porous and porous nanomaterials. In this work, we have explored the combination of mercaptosuccinic acid, an arsenic chelator, with zirconium oxo-clusters to assemble two new microporous Metal-Organic Frameworks (MOFs), denoted as BCM-1 and BCM-2 (BCM referring to Basque Center for Materials, Applications & Nanostructures). The specific chemical and structural features of these news frameworks have enabled controlling the arsenic loading and release in different scenarios. Specifically, arsenic release accelerates under oxidative conditions due to the rupture of thiol-arsenic bonds, caused by the oxidation of -SH groups to -SO3 within the MOF. Additionally, in acidic conditions typical of cancer microenvironments, the framework itself disassembles, further facilitating arsenic release. The particle size and arsenic loading capacity of BCM-1 can be easily modulated by controlling the synthesis conditions. This strategy has led to the development of micrometric, nanometric and gel-like materials, whose chemical stability in acidic and biological relevant media has been duly assessed. Notably, arsenic release from nano-BCM-1 is able to reverse the growth curve of HeLa cancer cells in approximately 50 h. This discovery paves the way towards the use of metal-chelator organic molecules in assembling new MOF materials capable of controlling the cargo and release of metallodrugs under in-vivo conditions.

Pseudopeptidic Coordination Polymers Based on Zirconium-Carboxylate Supramolecular Assemblies

Mimicking enzymes with new materials is a promising approach to improve efficiency and sustainability in heterogeneous catalysis. In this contribution, a family of coordination polymers based on N, N'-bis(amino acid)pyromellitic diimide linkers and Zr-oxo clusters has been assembled under solvothermal conditions in the presence of different acids (acetic, hydrochloric, and formic acid). The linker has been prepared from widely available amino acids and pyromellitic anhydride under microwave conditions. Different characterization techniques, such as NMR, Fourier transform infrared spectroscopy (FTIR), TGA, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM)/EDX, confirmed the formation of the pseudopeptidic (PSP) linkers and the subsequent formation of Zr-carboxylate bonds in the Zr-PSP coordination polymer, forming regular homogeneous nanoparticles with hybrid inorganic-organic composition. The PSPs have also been incorporated into defective UiO-67 crystals and employed as catalysts in the hydrolysis of p-nitrophenylacetate under mild conditions, exhibiting a correlation between porosity, residue volume, and activity.

Nonmetal Organic Frameworks Exhibit High Proton Conductivity

Porous materials, such as metal-organic frameworks (MOFs) and porous organic salts, are promising materials for proton conduction. Recently, we developed a new subclass of porous materials, isoreticular nonmetal organic frameworks (N-MOFs), which can be designed using crystal structure prediction (CSP). Here, two porous, isostructural, and water-stable halide N-MOFs were prepared and found to show good proton conductivity of up to 1.1 × 10-1 S cm-1 at 70 °C and 90% relative humidity. Changing the halides in these N-MOF materials affects the resulting proton conductivity, as observed in previous studies involving MOFs and lead halides. Although this is the first study of proton conductivity in N-MOFs, the bromide salt, TTBT.Br, shows a higher conductivity than most polycrystalline MOFs and porous organic salts, approaching that of Nafion.

pH-Dependent Structural Engineering of Sulfonate-Carboxylate Cu-MOFs for High Proton Conductivity

Metal-organic frameworks (MOFs) with free carboxylic acid (COOH) groups are promising for solid-state proton-conducting materials, owing to the Brønsted acidity, polarity, and the hydrogen-bonding ability of COOH groups. In this work, two Cu-MOFs with different dimensions were synthesized by adjusting the pH of the reaction solution using disodium-2,2'-disulfonate-4,4'-oxidibenzoic acid (Na2H2DSOA) and 4,4'-bipyridine (4,4'-bpy) as ligands to coordinate with Cu(II). The resulting compounds, CuDSOA-1 (([Cu(4,4'-bpy)2(H2O)2][Cu(H2DSOA)2(4,4'-bpy)(H2O)2]·12H2O)) and CuDSOA-2 ([Cu2(DSOA)(4,4'-bpy)2(H2O)2]·4H2O), have distinct dimensionalities and structures, mainly due to the pH's effect on carboxylic acid deprotonation. Notably, CuDSOA-1 with abundant COOH groups, uncoordinated sulfonate groups, and water molecules shows a significantly enhanced proton conductivity of 2.46 × 10-2 S cm-1 at 95 °C and 98% RH, surpassing CuDSOA-2 (3.40 × 10-5 S cm-1 at 85 °C and 98% RH). The conductivity mechanism was found to be a Grotthuss mechanism, confirmed by deuterium-hydrogen isotopic effects. This study offers a method to control the coordination of sulfonic-carboxylic acid ligands with Cu(II) by pH adjustment, aiming to create MOFs with ultrahigh proton conductivity.

Proton Conduction in Zirconium-Based Metal-Organic Frameworks for Advanced Applications

Zirconium-based metal-organic frameworks (Zr-MOFs) have emerged as a promising class of crystalline porous materials, attracting significant interest in the field of proton conduction due to their exceptional chemical stability, structural flexibility, and functional tunability. Notably, proton-conducting Zr-MOFs show immense potential for diverse advanced technological applications. In this Spotlight on Applications paper, we provide an overview of proton-conducting Zr-MOFs and spotlight the recent progress of their utilization as proton exchange membranes in proton exchange membrane fuel cells (PEMFCs), light-responsive systems for proton pumps, and chemical sensors for formic acid detection. Furthermore, we also discussed the challenges, future prospects, and opportunities for promoting the application of proton-conducting Zr-MOFs.

FIMOFs: Fiber-Integrated Metal-Organic Frameworks Through Electrospinning

Green synthesis plays a crucial role in advancing sustainability within materials science. This study explores the integration of metal-organic frameworks (MOFs), obtained through green synthesis, using an electrospinning post-processing technique to develop MOF-based composite materials. The resulting novel multifunctional composites demonstrate enhanced stability and functionality, compared to their control counterparts. The integration of four types of MOFs into an electrospun fiber network was investigated using a specific polymer solution. Characterization and preliminary adsorption studies were conducted to elucidate the chemistry, morphology, and adsorptive capabilities of the resulting MOF composites. Electrospinning MOFs into polymer fibers improved their stability and dye removal capabilities. More specifically, optimization of MOF-to-polymer ratios and processing conditions yielded composites that are thermally stable, with modified surface area and porosity. Post-processing MOFs resulted in a fiber diameter increase of 44 and 109%, enhancing the composites by providing more MOF active sites and improved mechanical strength. Zirconium-based post-processed MOFs demonstrated superior dye removal, different from the copper-based dyes. Electrospinning technology has demonstrated significant potential in the fabrication of high-performance multifunctional MOF composites. This has helped to create advanced sustainable composites with tailored properties, paving the way for more targeted and efficient applications. The applications of these composites show promise for military engineering where durable, light weight, and multifunctional materials are critical in contributing to improved performance, operational efficiency, and safety.

Functionalization of Defective Zr-MOFs for Water Decontamination: Mechanistic Insight into the Competitive Roles of -NH2 and -SH Sites in the Removal of Hg(II) Ions

Functional metal-organic frameworks (MOFs), especially those based on sulfur and nitrogen atoms, were frequently applied for the removal of Hg(II) ions. However, a systematic study on the cooperative or competitive roles of -SH and -NH2 functions in the presence of secondary mechanisms (proton transfer and redox) is still rare. In this work, the UiO-66 framework (Zr6(OH)4O4(BDC)6, BDC2- = benzene-1,4-dicarboxylate) was decorated with functional monocarboxylate linkers including glycine (Gly), mercaptopropionic acid (Mer), and cysteine (Cys). Due to the molecular similarity of these functional linkers, the coordination affinity between the amine and thiol sites with Hg(II) ions can be compared, and the effect of proton transfer and redox mechanisms on the possible thiol···Hg(II) and amine···Hg(II) interactions can be investigated. The results show that the Cys@UiO-66 framework can adsorb 1288 mg g-1 of Hg(II), while Mer@UiO-66 and Gly@UiO-66 can adsorb 593 and 313 mg g-1 at pH = 7 and 500 ppm, respectively. This is due to the facts that both the amine and the thiol functions of the Cys@UiO-66 framework show synergism in Hg(II) removal, and the secondary mechanisms reduce the affinity of thiol in Mer@UiO-66 and amine in Gly@UiO-66 frameworks in the removal process of Hg(II) ions. Free -SH sites in Mer@UiO-66 undergo a redox convert to -SO3H groups, and free protonated -NH2 sites in Gly@UiO-66 do not fully deprotonate during Hg(II) removal. Yet, in the case of Cys@UiO-66, free protonated -NH2 sites are fully deprotonated, and free SH sites did not convert to -SO3H groups during Hg(II) removal. These observations show that the redox and proton transfer mechanisms can negatively affect the adsorption capacity of functional MOFs containing free -SH and -NH2 groups. So, not only the functionalization but also control over secondary mechanisms in the removal process are necessary parameters to improve the affinity between functional MOFs and Hg(II) ions.

Linkage Position-Controlled Synthesis of Diverse Zirconium Metal-Organic Frameworks with Prominent Intrinsic Proton Conductivities

Herein, by engineering the geometries of the organic linkers, two pyrrolo-pyrrole-based low-symmetry tetracarboxylate linkers (TAPPs) were successfully designed and subsequently used for the construction of two new zirconium-based metal-organic frameworks (Zr-MOFs) (IAM-10 and IAM-11). The reduction of the linker symmetry arises from both the asymmetric pyrrolo-pyrrole core and the integration of both the para- and meta-benzoate coordination groups on the linkers. Both MOFs are composed of 8-connected Zr6 nodes and 4-connected highly deformed TAPP4- linkers with the same scu topology, but distinct linker arrangements can be observed in two structures. The specific rhomb-shaped geometry together with the flexible m-benzoate groups through the rotation of the peripheral phenyl rings allows this type of TAPP linker to generate unique conformations and arrangements in MOF structures to optimize the coordination bonds with the inorganic building blocks and adapt to the final topologies. Furthermore, the presence of well-defined hydrophilic channels in the reported MOFs allowed us to evaluate the potential for proton conduction. Both IAM-10 and IAM-11 show the prominent intrinsic proton conductivities of 1.13 × 10-2 and 2.69 × 10-3 S cm-1 at 90 °C and 95% RH, making them the top-performing proton-conductive Zr-MOFs.

Superior proton conductivity of amino acid-modified UiO-66-(COOH)2 embedded in chitosan: Mechanistic insights into the acid-base interactions

We focus on optimizing acid-base interactions and hydrogen bonding networks to achieve enhanced proton conductivity under low relative humidity (RH) and high temperature. By functionalizing UiO-66-(COOH)2 with glutamic acid (Glu) and lysine (Lys), we generate Glu-UiO-66-(COOH)2 and Lys-UiO-66-(COOH)2. These modified materials are subsequently incorporated into chitosan (CS) to produce the composites Glu-UiO-66-(COOH)2@CS and Lys-UiO-66-(COOH)2@CS. The successful incorporation of amino acids and cross-linking between -COOH and -NH2 groups in the composites, confirmed by FTIR and PXRD analyses, significantly enhances the structural integrity and durability by strengthening the network, and reducing polymer chain mobility. Proton conductivity assessments reveal that Lys-UiO-66-(COOH)2@CS-7 exhibits a remarkable conductivity of 0.022 S/cm at 100 % RH and 363 K, outperforming Glu-UiO-66-(COOH)2@CS-7. The lower activation energy (Ea) of 0.28 eV for Lys-UiO-66-(COOH)2@CS-7, compared to 0.336 eV for Glu-UiO-66-(COOH)2@CS-7, highlights the significant improvement in intramolecular acid-base interactions and hydrogen bonding. Furthermore, Lys-UiO-66-(COOH)2@CS-7 maintains notable proton conductivity at 43 % RH, with an Ea of 0.216 eV, demonstrating its efficacy in low-humidity conditions. These findings underscore the profound impact of amino acid modifications and cross-linking on proton conductivity by reinforcing acid-base interactions, hydrogen bonding networks, and proton transfer efficiency.

Precision-Engineered Construction of Proton-Conducting Metal-Organic Frameworks

Proton-conducting materials have attracted considerable interest because of their extensive application in energy storage and conversion devices. Among them, metal-organic frameworks (MOFs) present tremendous development potential and possibilities for constructing novel advanced proton conductors due to their special advantages in crystallinity, designability, and porosity. In particular, several special design strategies for the structure of MOFs have opened new doors for the advancement of MOF proton conductors, such as charged network construction, ligand functionalization, metal-center manipulation, defective engineering, guest molecule incorporation, and pore-space manipulation. With the implementation of these strategies, proton-conducting MOFs have developed significantly and profoundly within the last decade. Therefore, in this review, we critically discuss and analyze the fundamental principles, design strategies, and implementation methods targeted at improving the proton conductivity of MOFs through representative examples. Besides, the structural features, the proton conduction mechanism and the behavior of MOFs are discussed thoroughly and meticulously. Future endeavors are also proposed to address the challenges of proton-conducting MOFs in practical research. We sincerely expect that this review will bring guidance and inspiration for the design of proton-conducting MOFs and further motivate the research enthusiasm for novel proton-conducting materials.

Chiral Supramolecular Proton Conductors: Harnessing Highly Charged Zirconium-Amino Acid Oxo-Clusters

Incorporation of amino acid capping molecules (alanine (Ala), methionine (Met), phenylalanine (Phe), tryptophan (Trp), tyrosine (Tyr), and valine (Val)) in their zwitterionic form into archetypal [Zr6(μ3-O)4(μ3-OH)4]12+ clusters creates supramolecular frameworks in which the assembly of these highly charged discrete units with chloride counterions provides a unique combination of porosity, chirality, and proton conductivity. The supramolecular frameworks assembled from these cluster entities (i.e., ZrAla, ZrMet, ZrPhe, ZrTrp, ZrTyr, and ZrVal) are based on the counterbalancing of the cationic hexanuclear entities by chloride anions. The resulting structures provide porous structures (except ZrVal) with variability of chemical and structural stability based on their supramolecular interactions. Among these compounds, ZrPhe and ZrVal remain stable due to the presence of a double chelation-like interaction involving four hydrogen bonds formed between a chloride anion, two ammonium groups, and two coordinated water molecules from two adjacent hexanuclear units. The presence of multiple acidic proton positions and strong hydrogen-bond donor/acceptor groups on the water channels gives rise to easy proton conduction pathways within the structures. In fact, ZrPhe and ZrVal, together with ZrTyr, exhibit high proton conductivity values with varying dependencies on the atmospheric humidity. Finally, the correlation between proton conduction and porosity is discussed.

Chrome-free leather processing based on amine pendant metal-organic frameworks and dialdehyde with enhanced dye affinity

To overcome the stringent regulations in the usage of chromium salts and dye-rich effluent let out by the tanning industry, a sustainable way of leather processing has been demonstrated utilizing amine pendant metal-organic frameworks (MOF) UiO-66-NH2 along with glyoxal. It was found that an offer of 8% (w/w) MOF along with 6% (w/w) glyoxal increased the shrinkage temperature of the leathers to 89 ± 2 °C with exhaustion of MOF up to 84.3 ± 1.5%. The presence of cationic amine sites in the MOF aided in the fixation of anionic post-tanning agents and improved the adsorption of dyes from 74.3 ± 2.5% in the case of conventional leather to 91.8 ± 1.7% for experimental leather. In comparison to chrome-tanned leather, the experimental leathers were rated the highest in terms of dye fastness concerning rubbing action and against perspiration, showcasing the washable properties and better affinity and irreversible binding of dyes to the leather matrix. Mechanism studies through XPS spectroscopy revealed the interaction between the acidic amino acids of collagen and free zirconium metal sites and the imine linkage between amine pendants of MOF and basic amino acids of collagen protein. Further, the BOD5/COD ratio of 0.36 confirmed the better treatability of the wastewater emanating from the proposed process making it a sustainable tanning system. Thus, the combination of amine pendant MOFs with dialdehyde can be a promising strategy for the development of robust chrome-free leathers with excellent functional properties.

Application of zirconium aspartic acid metal-organic framework (MIP-202(Zr)) for high efficient ruthenium adsorption from aqueous solutions

The zirconium metal - organic framework MIP-202(Zr), based on L-aspartic acid, was prepared by hydrothermal method and used for study of ruthenium adsorption from aqueous solutions. The obtained material was characterized by X-ray diffraction (XRD), infra red spectroscopy (IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The batch adsorption experiment was performed for determination of adsorption equilibrium, kinetics and thermodynamics parameters to Ru(III) from aqueous solution on MIP-202(Zr). The data of ruthenium sorption onto MIP-202(Zr) were fitted and analyzed by the Langmuir, Freundlich and Temkin equilibrium isotherm models, while the Langumir adsorption isotherm models fit the best. Kinetic data were analyzed by four kinetic models, and ruthenium sorption on MIP202(Zr) can be describes the best by intra particle diffusion (Weber Morris). Analysis of thermodynamic properties of ruthenium ions sorption onto MIP-202(Zr) shows that the sorption process has a spontaneous and endothermic nature and is energetically beneficial.

Copper-based photocatalysts with natural organic ligands for efficient removal of tetracycline under visible light

The excessive use of broad-spectrum antibiotics, such as tetracycline, presents a significant challenge to human survival and development. Oxygen vacancies (OVs) metal-organic framework (MOF) materials were synthesized using natural organic acids (L-malic acid, L-aspartic acid, and L-asparagine) with similar structures but different charge densities, along with copper as the metal linking agent. The presence of oxygen vacancies in the catalyst provides abundant active sites for photocatalytic reactions. The employment of flexible straight-chain organic ligands devoid of rigid polycyclic rings, combined with the incorporation of different substituents to induce variations in charge density, the resulting catalysts exhibit distinct photocatalytic activities under visible light. Density functional theory calculations confirm that L-asparagine exhibits the largest electron density difference, and the Cu-based MOF (Cu-ASU) synthesized as an organic ligand exhibits the highest photocatalytic activity under visible light excitation. The catalyst displayed remarkable photocatalytic activity against tetracycline antibiotics under identical conditions (with removal rates of 93.5 % for tetracycline, 81.4 % for terramycin, and 95.6 % for chloramphenicol hydrochloride). This provides a novel approach for the design and synthesis of photocatalysts for the removal of antibiotics from water.

Systematic design and functionalisation of amorphous zirconium metal-organic frameworks

Controlling the structure and functionality of crystalline metal-organic frameworks (MOFs) using molecular building units and post-synthetic functionalisation presents challenges when extending this approach to their amorphous counterparts (aMOFs). Here, we present a new bottom-up approach for synthesising a series of Zr-based aMOFs, which involves linking metal-organic clusters with specific ligands to regulate local connectivity. In addition, we overcome the limitations of post-synthetic modifications in amorphous systems, demonstrating that homogeneous functionalisation is achievable even without regular internal voids. By altering the acidity of the side group, length, and degree of connectivity of the linker, we could control the porosity, proton conductivity, and mechanical properties of the resulting aMOFs.

Functionalized metal-organic frameworks with biomolecules for sensing and detection applications of food contaminants

The increasing demand for toxin-free food, driven by the rise in fast food consumption and changing dietary habits, necessitates advanced and efficient detection methods to address the potential risks associated with contaminated food. Nanomaterial-based detection methods have shown significant promise, particularly using metal-organic frameworks (MOFs) combined with biomolecules. This review article provides an overview of recent advancements in using functionalized metal-organic frameworks (FMOFs) with biomolecules to detect various food contaminants, including heavy metals, antibiotics, pesticides, bacteria, mycotoxins and other chemical contaminants. We discuss the fundamental principles of detecting food contaminants, evaluate existing analytical techniques, and explore the development of biomacromolecule-functionalized MOF-based sensors encompassing colorimetric, optical, electrochemical, and portable variants. The review also examines sensing mechanisms, uses FMOFs as signal probes and carriers for capture probes, and assesses sensitivity. Additionally, we explore the opportunities and challenges in producing FMOFs with biomacromolecules for food contaminant assessment. Future directions include improving sensor sensitivity and specificity, developing more cost-effective production methods, and integrating these technologies into real-world food safety monitoring systems. This work aims to pave the way for innovative and reliable solutions to ensure the safety of our food supply.

Combined Effect of Hydrophilic Pore and the Type of Protons on Proton Conductivity in Porous Metal-Organic Frameworks: A Feasible Approach to Achieve a Super Proton Conductor under Hydrated Conditions

There has been a steady growth of interest in proton-conductive metal-organic frameworks (MOFs) due to their potential utility in proton-exchange membrane fuel cells. To attain a super proton conductivity (>1 × 10-2 S cm-1) in a MOF-based proton conductor is a key step toward practical application. Currently, most studies are focused on enhancing the proton conductivity of porous MOFs by controlling a single factor, such as the type of protons or hydrophilic pore or hydrogen bond. However, a limited contribution from a single factor cannot afford to remarkably increase the proton conductivity of the MOF and form a super proton conductor. Herein, we constructed two distinct porous MOFs, {(H3O+)4[Cu12(ci)12(OH)4(H2O)12]·3H2O·9DMF} (Cu-ci-3D, H2ci = 1H-indazole-5-carboxylic acid, DMF = N,N'-dimethylformamide) and {[Co(Hppca)2]·2HN(CH3)2·CH3OH·2H2O} (Co-ppca-2D, H2ppca = 5-(pyridin-3-yl)-1H-pyrazole-3-carboxylic acid), to tune their proton conductivities at high relative humidity (RH) using the combined effect of hydrophilic pore and the type of protons, ultimately achieving super proton conduction. Excitingly, Cu-ci-3D indeed harvests a super proton conductivity of 1.37 × 10-2 S cm-1 at 353 K and ∼97% RH, superior to some previously reported MOF-based proton conductors. The results present a unique perspective for developing high-performance MOF-based proton conductors and understanding their structure-performance relationships.

Kinetic and stability studies of amino acid metal-organic frameworks for encapsulating of amino acid dehydrogenase

Zr-MOFs was applied for the immobilization of hyperthermophilic and halophilic amino acid dehydrogenase (Zr-MOFs-NTAaDH) by physical adsorption for the biosynthesis of L-homophenylalanine. Activity of Zr-MOFs-NTAaDH was enhanced by 3.3-fold of the free enzyme at 70°C. And the enzyme activity of Zr-MOFs-NTAaDH was maintained at 4.16 U/mg at pH 11, which was 7.8 folds of that of NTAaDH. Kinetic parameters indicated catalytic efficiency of Zr-MOFs-NTAaDH was increased compared to the free enzyme as kcat of Zr-MOFs-NTAaDH was 12.3-fold of that of free enzyme. After 7 recycles, the activity of Zr-MOFs-NTAaDH remained 68 %. And Zr-MOFs-NTAaDH exhibited high ionic liquid tolerance which indicated the great potential for industrial application.

Superior and efficient performance of cost-effective MIP-202 catalyst over UiO-66-(CO2H)2 in epoxide ring opening reactions

This study explored the catalytic performance of two robust zirconium-based metal-organic frameworks (MOFs), MIP-202(Zr) and UiO-66-(CO2H)2 in the ring-opening of epoxides using alcohols and amines as nucleophilic reagents. The MOFs were characterized by techniques such as FT-IR, PXRD, FE-SEM, and EDX. Through systematic optimization of key parameters (catalyst amount, time, temperature, solvent), MIP-202(Zr) achieved 99% styrene oxide conversion in 25 min with methanol at room temperature using 5 mg catalyst. In contrast, UiO-66-(CO2H)2 required drastically harsher conditions of 120 min, 60 °C, and four times the catalyst loading to reach 98% conversion. A similar trend was observed for ring-opening with aniline -MIP-202(Zr) gave 93% conversion in one hour at room temperature, while UiO-66-(CO2H)2 needed two hours at 60 °C for 95% conversion. The superior performance of MIP-202(Zr) likely stems from cooperative Brønsted/Lewis acid sites and higher proton conductivity enabling more efficient epoxide activation. Remarkably, MIP-202(Zr) maintained consistent activity over five recycles in the ring-opening of styrene oxide by methanol and over three recycles in the ring-opening of styrene oxide by aniline. Testing various epoxide substrates and nucleophiles revealed trends in reactivity governed by electronic and steric effects. The results provide useful insights into tuning Zr-MOF-based catalysts and highlight the promise of the cost-effective and sustainable MIP-202(Zr) for diverse epoxide ring-opening reactions on an industrial scale.

Prominent Intrinsic Proton Conduction in Two Robust Zr/Hf Metal-Organic Frameworks Assembled by Bithiophene Dicarboxylate

To date, developing crystalline proton-conductive metal-organic frameworks (MOFs) with an inherent excellent proton-conducting ability and structural stability has been a critical priority in addressing the technologies required for sustainable development and energy storage. Bearing this in mind, a multifunctional organic ligand, 3,4-dimethylthiophene[2,3-b]thiophene-2,5-dicarboxylic acid (H2DTD), was employed to generate two exceptionally stable three-dimensional porous Zr/Hf MOFs, [Zr6O4(OH)4(DTD)6]·5DMF·H2O (Zr-DTD) and [Hf6O4(OH)4(DTD)6]·4DMF·H2O (Hf-DTD), using solvothermal means. The presence of Zr6 or Hf6 nodes, strong Zr/Hf-O bonds, the electrical influence of the methyl group, and the steric effect of the thiophene unit all contribute to their structural stability throughout a wide pH range as well as in water. Their proton conductivity was fully examined at various relative humidities (RHs) and temperatures. Creating intricate and rich H-bonded networks between the guest water molecules, coordination solvent molecules, thiophene-S, -COOH, and -OH units within the framework assisted proton transfer. As a result, both MOFs manifest the maximum proton conductivity of 0.67 × 10-2 and 4.85 × 10-3 S·cm-1 under 98% RH/100 °C, making them the top-performing proton-conductive Zr/Hf-MOFs. Finally, by combining structural characteristics and activation energies, potential proton conduction pathways for the two MOFs were identified.

Two histidine-templated metal phosphate-oxalates: solvent-free synthesis, luminescence, and proton-conducting properties

Two new histidine-templated metal phosphate-oxalates (MPOs) were prepared under solvent-free conditions. Single-crystal X-ray diffraction analysis reveals that they have layered and chainlike structures, respectively. Under ultraviolet light irradiation, the two MPOs exhibit blue luminescence originating from histidine templates. Their proton-conducting properties were also investigated under different conditions.

Metal-Drug Coordination Nanoparticles and Hydrogels for Enhanced Delivery

Drug delivery is a key component of nanomedicine, and conventional delivery relies on the adsorption or encapsulation of drug molecules to a nanomaterial. Many delivery vehicles contain metal ions, such as metal-organic frameworks, metal oxides, transition metal dichalcogenides, MXene, and noble metal nanoparticles. These materials have a high metal content and pose potential long-term toxicity concerns leading to difficulties for clinical approval. In this review, recent developments are summarized in the use of drug molecules as ligands for metal coordination forming various nanomaterials and soft materials. In these cases, the drug-to-metal ratio is much higher than conventional adsorption-based strategies. The drug molecules are divided into small-molecule drugs, nucleic acids, and proteins. The formed hybrid materials mainly include nanoparticles and hydrogels, upon which targeting ligands can be grafted to improve efficacy and further decrease toxicity. The application of these materials for addressing cancer, viral infection, bacterial infection inflammatory bowel disease, and bone diseases is reviewed. In the end, some future directions are discussed from fundamental research, materials science, and medicine.

Room-Temperature Superprotonic Conductivity beyond 10-1 S cm-1 in a Co(II) Coordination Polymer

An efficient design of crystalline solid-state proton conductors (SSPCs) is crucial for the progress of clean energy applications. Developing such materials to make them work at room temperature with a conductivity of ≥10-1 S cm-1 is of significant interest in terms of technical and commercial aspects. Utilizing the recently highlighted "coordinated-water-driven proton conduction" approach, herein, we have rationally synthesized two highly stable and scalable 1D Co(II) coordination polymers (CPs) as SSPCs, PCM-2 {[Co(bpy)(H2O)2(NO3)2]·H2O}n and PCM-3 {[Co2(bpy)2(SO4)2(H2O)6].4H2O}n, with distinct alignments in coordinated water and coordinated oxo-anions (nitrate and sulfate, respectively). The acidity of the metal-bound water molecules in PCM-2 is further enhanced through cooperative long-range continuous H bonds with coordinated Brønsted basic nitrates (proton acceptors), leading to ultrahigh superprotonic conductivities even at 25 °C (1.03 × 10-1 S cm-1 under 95% RH), and reached a maximum of 2.99 × 10-1 S cm-1 at 85 °C (95% RH). The conductivity at 25 °C is even higher than that of commercial Nafion 117 (6.74 × 10-2 S cm-1 at 100% RH). The absence of such an H-bonding interaction in PCM-3 (closed loops) resulted in a lesser conductivity of 5.87 × 10-5 S cm-1 (95% RH, 85 °C). PCM-2 represents the first example of SSPC exhibiting conductivity in the order 10-1 S cm-1 at ambient temperature (25 °C) with excellent recyclability.

Water-Resistant, Scalable, and Inexpensive Chiral Metal-Organic Framework Featuring Global Negative Electrostatic Potentials for Efficient Acetylene Separation

Physical separation of acetylene (C2H2) from carbon dioxide (CO2) or ethylene (C2H4) on metal-organic frameworks (MOFs) is crucial for achieving high-purity feed gases with minimal energy penalty. However, such processes are exceptionally challenging due to their close physical properties and are also critically restricted by the high cost of large-scale MOF synthesis. Here, we demonstrate the readily scalable synthesis of a highly water-resistant chiral Cu-MOF (TAMOF-1) based on an inexpensive proteogenic amino acid derivative bearing rich N/O sites. Notably, the unique coordination in this ultramicroporous MOF has resulted in the generation of rare global negative electrostatic potentials, which greatly facilitate the electrostatic interactions with C2H2 molecules, thus leading to their efficient separation from C2H2/CO2 and C2H2/C2H4 mixtures under ambient conditions. The separation efficiency and mechanism are unequivocally validated by breakthrough experiments and computational simulations. This work not only highlights the pivotal role of creating a negative electro-environment in confined spaces for boosting C2H2 capture and separation but also opens up new ways of employing cheap amino acid derivatives bearing rich electro-negative N and O sites as organic linkers to constructing high-performing MOF materials for gas separation purposes.

Construction of Hydration Layer for Proton Transport by Implanting the Hydrophilic Center Ag0 in Nickel Metal-Organic Frameworks

The directional arrangement of H2O molecules can effectively regulate the ordered protons transfer to improve transport efficiency, which can be controlled by the interaction between materials and H2O. Herein, a strategy to build a stable hydration layer in metal-organic framework (MOF) platforms, in which hydrophilic centers that can manipulate H2O molecules are implanted into MOF cavities is presented. The rigid grid-Ni-MOF is selected as the supporting material due to the uniformly distributed cavities and rigid structures. The Ag0 possesses potential combination ability with the hydrophilic substances, so it is introduced into the MOF as hydration layer centers. Relying on the strong interaction between Ag0 and H2O, the H2O molecules can rearrange around Ag0 in the cavity, which is intuitively verified by DFT calculation and molecular dynamics simulation. The establishment of a hydration layer in Ag@Ni-MOF regulates the chemical properties of the material and gives the material excellent proton conduction performance, with a proton conductivity of 4.86 × 10-2 S cm-1.

Application of a magnetically separable Zr-MOF for fast extraction of palladium before its spectrophotometric detection

In this research, a novel magnetic zirconium-based metal-organic framework (Fe3O4@SiO2@MIP-202, MMOF), was fabricated, fully characterized, and applied for the batch-mode solid phase extraction of trace amounts of Pd2+ ions from water and wastewater samples before its spectrophotometric detection. Pd2+ ions were desorbed from MMOF by nitric acid and were complexed by treating with KI solution to have a maximum absorbance at 410 nm. The synthesized MMOF composite showed a very large surface area (65 m2.g- 1), good magnetization (1.7 emu.g- 1) and a large pore volume (0.059 cm3.g- 1) with adsorption capacity of 194.5 mg of Pd2+ ions/g of the adsorbent. This nanosorbent boasts chemo-mechanical stability, high adsorption capacity due to its vast active sites, and facile recovery facilitated by its magnetic properties. Parameters affecting the extraction efficiency of the method were optimized as pH of the sample 7.4, volume of the sample 25 mL, 15 mg adsorbent, 1 mL of 0.1 M HNO3 eluent, with 10 and 15 min as the extraction and desorption times, respectively. The calibration curve was found to be linear across the 10.0-1500.0 µg.L- 1 range with a limit of detection of 1.05 µg.L- 1. The obtained extraction efficiency and enrichment were 98% and 245, respectively. The total analysis time was less than 30 min. This MMOF has never been used for the extraction of Pd2+ ions before.

Biomolecules meet organic frameworks: from synthesis strategies to diverse applications

Biomolecules are essential in pharmaceuticals, biocatalysts, biomaterials, etc., but unfortunately they are extremely susceptible to extraneous conditions. When biomolecules meet porous organic frameworks, significantly improved thermal, chemical, and mechanical stabilities are not only acquired for raw biomolecules, but also molecule sieving, substrate enrichment, chirality property, and other functionalities are additionally introduced for application expansions. In addition, the intriguing synergistic effect stemming from elaborate and concerted interactions between biomolecules and frameworks can further enhance application performances. In this paper, the synthesis strategies of the so-called bio-organic frameworks (BOFs) in recent years are systematically reviewed and classified. Additionally, their broad applications in biomedicine, catalysis, separation, sensing, and imaging are introduced and discussed. Before ending, the current challenges and prospects in the future for this infancy-stage but significant research field are also provided. We hope that this review will offer a concise but comprehensive vision of designing and constructing multifunctional BOF materials as well as their full explorations in various fields.

Heating-induced adsorption promoting the efficient removal of toluene by the metal-organic framework UiO-66 (Zr) under visible light

The removal of indoor/outdoor toluene by photocatalysis has drawn much attention due to its low energy consumption and easy availability. However, light inevitably generates heat, and pollutants desorb from catalysts as the temperature rises, which is not beneficial to degradation. Contrast to the frequently occurred phenomena, we firstly found that the adsorption capacity of UiO-66 (Zr) on toluene increased with increasing temperature as adsorption isotherms and in-situ Fourier transform infrared spectra (in-situ FTIR) showed. The optimum temperature was 30 °C. This stage in which adsorption capacity was positively correlated with temperature was called heating-induced adsorption, which achieved a toluene removal efficiency of 69.6 %. By density functional theory (DFT) calculations and changing the metal centers and organic ligands of UiO-66 (Zr) respectively, we disclosed that the heating-induced adsorption was mainly related to the π-π stacking interaction of MOF ligands and toluene. The analysis of samples before and after adsorption showed that the interaction between UiO-66 (Zr) and adsorbed toluene facilitated the charge transfer and prolonged the carrier lifetime, leading to the increase of hydroxyl radicals (•OH) in photocatalysis. Therefore, a synergistic effect between heating-induced adsorption and photocatalysis was proposed by analyzing the adsorption of toluene on UiO-66 (Zr) in detail. This work provided new viewpoint to understand the role of concomitant heat contributed to the adsorption and degradation of toluene during photocatalysis.

Green Synthesis of pH-Responsive Metal-Organic Frameworks for Delivery of Diclofenac Sodium

The current study developed a drug delivery system through the green chemistry-based synthesis of a biologically friendly metal-organic framework (bio-MOF) called Asp-Cu, which included copper ions and the environmentally friendly molecule L(+)-aspartic acid (Asp). For the first time, diclofenac sodium (DS) was loaded onto the synthesized bio-MOF simultaneously. The system's efficiency was then improved by encapsulating it with sodium alginate (SA). FT-IR, SEM, BET, TGA, and XRD analyses confirmed that DS@Cu-ASP was successfully synthesized. DS@Asp-Cu was found to release the total load within 2 h when used with simulated stomach media. This challenge was overcome by coating DS@Cu-ASP with SA (SA@DS@Cu-ASP). SA@DS@Cu-ASP displayed limited drug release at pH 1.2, and a higher percentage of the drug was released at pH 6.8 and 7.4 due to the pH-responsive nature of SA. In vitro cytotoxicity screening showed that SA@DS@Cu-ASP could be an appropriate biocompatible carrier with >90% cell viability. The on-command drug carrier was observed to be more applicable biocompatible with lower toxicity, as well as adequate loading properties and responsiveness, indicating its applicability as a feasible drug carrier with controlled release.

Trajectory in biological metal-organic frameworks: Biosensing and sustainable strategies-perspectives and challenges

The ligand attribute of biomolecules to form coordination bonds with metal ions led to the discovery of a novel class of materials called biomolecule-associated metal-organic frameworks (Bio-MOFs). These biomolecules coordinate in multiple ways and provide versatile applications. Far-spread bio-ligands include nucleobases, amino acids, peptides, cyclodextrins, saccharides, porphyrins/metalloporphyrin, proteins, etc. Low-toxicity, self-assembly, stability, designable and selectable porous size, the existence of rigid and flexible forms, bio-compatibility, and synergistic interactions between metal ions have led Bio-MOFs to be commercialized in industries such as sensors, food, pharma, and eco-sensing. The rapid growth and commercialization are stunted by absolute bio-compatibility issues, bulk morphology that makes it rigid to alter shape/porosity, longer reaction times, and inadequate research. This review elucidates the structural vitality, biocompatibility issues, and vital sensing applications, including challenges for incorporating bio-ligands into MOF. Critical innovations in Bio-MOFs' applicative spectrum, including sustainable food packaging, biosensing, insulin and phosphoprotein detection, gas sensing, CO2 capture, pesticide carriers, toxicant adsorptions, etc., have been elucidated. Emphasis is placed on biosensing and biomedical applications with biomimetic catalysis and sensitive sensor designing.

The green synthesis and applications of biological metal-organic frameworks for targeted drug delivery and tumor treatments

Biological metal-organic frameworks (bio-MOFs) constitute a growing subclass of MOFs composed of metals and bio-ligands derived from biology, such as nucleobases, peptides, saccharides, and amino acids. Bio-ligands are more abundant than other traditional organic ligands, providing multiple coordination sites for MOFs. However, bio-MOFs are typically prepared using hazardous or harmful solvents or reagents, as well as laborious processes that do not conform to environmentally friendly standards. To improve biocompatibility and biosafety, eco-friendly synthesis and functionalization techniques should be employed with mild conditions and safer materials, aiming to reduce or avoid the use of toxic and hazardous chemical agents. Recently, bio-MOF applications have gained importance in some research areas, including imaging, tumor therapy, and targeted drug delivery, owing to their flexibility, low steric hindrances, low toxicity, remarkable biocompatibility, surface property refining, and degradability. This has led to an exponential increase in research on these materials. This paper provides a comprehensive review of updated strategies for the synthesis of environmentally friendly bio-MOFs, as well as an examination of the current progress and accomplishments in green-synthesized bio-MOFs for drug delivery aims and tumor treatments. In conclusion, we consider the challenges of applying bio-MOFs for biomedical applications and clarify the possible research orientation that can lead to highly efficient therapeutic outcomes.

Oriented Self-assembly of Flexible MOFs Nanocrystals into Anisotropic Superstructures with Homogeneous Hydrogels Behaviors

Building of metal-organic frameworks (MOFs) homogeneous hydrogels made by spontaneous crystallization remains a significant challenge. Inspired by anisotropically structured materials in nature, an oriented super-assembly strategy to construct micro-scale MOFs superstructure is reported, in which the strong intermolecular interactions between zirconium-oxygen (Zr─O) cluster and glutamic acid are utilized to drive the self-assembly of flexible nanoribbons into pumpkin-like microspheres. The confined effect between water-flexible building blocks and crosslinked hydrogen networks of superstructures achieved a mismatch transformation of MOFs powders into homogeneous hydrogels. Importantly, the elastic and rigid properties of hydrogels can be simply controlled by precise modulation of coordination and self-assembly for anisotropic superstructure. Experimental results and theoretical calculations demonstrates that MOFs anisotropic superstructure exhibits dynamic double networks with a superior water harvesting capacity (119.73 g g-1 ) accompanied with heavy metal removal (1331.67 mg g-1 ) and strong mechanical strength (Young's modulus of 0.3 GPa). The study highlights the unique possibility of tailoring MOFs superstructure with homogeneous hydrogel behavior for application in diverse fields.

A Multifunctional Co-Based Metal-Organic Framework as a Platform for Proton Conduction and Ni trophenols Reduction

The design and development of proton conduction materials for clean energy-related applications is obviously important and highly desired but challenging. An ultrastable cobalt-based metal-organic framework Co-MOF, formulated as [Co2(btzip)2(μ2-OH2)] (namely, LCUH-103, H2btzip = 4, 6-bis(triazol-1-yl)-isophthalic acid) had been successfully synthesized via the hydrothermal method. LCUH-103 exhibits a three-dimensional framework and a one-dimensional microporous channel structure with scu topology based on the binuclear metallic cluster {Co2}. LCUH-103 indicated excellent chemical and thermal stability; peculiarly, it can retain its entire framework in acid and alkali solutions with different pH values for 24 h. The excellent stability is a prerequisite for studying its proton conductivity, and its proton conductivity σ can reach up to 1.25 × 10-3 S·cm-1 at 80 °C and 100% relative humidity (RH). In order to enhance its proton conductivity, the proton-conducting material Im@LCUH-103 had been prepared by encapsulating imidazole molecules into the channels of LCUH-103. Im@LCUH-103 indicated an excellent proton conductivity of 3.18 × 10-2 S·cm-1 at 80 °C and 100% RH, which is 1 order of magnitude higher than that of original LCUH-103. The proton conduction mechanism was systematically studied by various detection means and theoretical calculations. Meanwhile, LCUH-103 is also an excellent carrier for palladium nanoparticles (Pd NPs) via a wetness impregnation strategy, and the nitrophenols (4/3/2-NP) reduction in aqueous solution by Pd@LCUH-103 indicated an outstanding conversion efficiency, high rate constant (k), and exceptional cycling stability. Specifically, the k value of 4-NP reduction by Pd@LCUH-103 is superior to many other reported catalysts, and its k value is as high as 1.34 min-1 and the cycling stability can reach up to 6 cycles. Notably, its turnover frequency (TOF) value is nearly 196.88 times more than that of Pd/C (wt 5%) in the reaction, indicating its excellent stability and catalytic activity.

A Pair of Multifunctional Cu(II)-Dy(III) Enantiomers with Zero-Field Single-Molecule Magnet Behaviors, Proton Conduction Properties and Magneto-Optical Faraday Effects

Multifunctional materials with a coexistence of proton conduction properties, single-molecule magnet (SMM) behaviors and magneto-optical Faraday effects have rarely been reported. Herein, a new pair of Cu(II)-Dy(III) enantiomers, [DyCu2(RR/SS-H2L)2(H2O)4(NO3)2]·(NO3)·(H2O) (R-1 and S-1) (H4L = [RR/SS] -N,N'-bis [3-hydroxysalicylidene] -1,2-cyclohexanediamine), has been designed and prepared using homochiral Schiff-base ligands. R-1 and S-1 contain linear Cu(II)-Dy(III)-Cu(II) trinuclear units and possess 1D stacking channels within their supramolecular networks. R-1 and S-1 display chiral optical activity and strong magneto-optical Faraday effects. Moreover, R-1 shows a zero-field SMM behavior. In addition, R-1 demonstrates humidity- and temperature-dependent proton conductivity with optimal values of 1.34 × 10-4 S·cm-1 under 50 °C and 98% relative humidity (RH), which is related to a 1D extended H-bonded chain constructed by water molecules, nitrate and phenol groups of the RR-H2L ligand.

Application of Conductive MOF in Zinc-Based Batteries

The use of conductive MOFs (c-MOFs) in zinc-based batteries has been a popular research direction. Zinc-based batteries are widely used with the advantages of high specific capacity and safety and stability, but they also face many problems. c-MOFs have excellent conductivity compared with other primitive MOFs, and therefore have better applications in zinc-based batteries. In this paper, the transfer mechanisms of the unique charges of c-MOFs: hop transport and band transport, respectively, are discussed and the way of electron transport is further addressed. Then, the various ways to prepare c-MOFs are introduced, among which solvothermal, interfacial synthesis, and postprocessing methods are widely used. In addition, the applications of c-MOFs are discussed in terms of their role and performance in different types of zinc-based batteries. Finally, the current problems of c-MOFs and the prospects for their future development are presented.

Versatile Protein and Its Subunit Biomolecules for Advanced Rechargeable Batteries

Rechargeable batteries are of great significance for alleviating the growing energy crisis by providing efficient and sustainable energy storage solutions. However, the multiple issues associated with the diverse components in a battery system as well as the interphase problems greatly hinder their applications. Proteins and their subunits, peptides, and amino acids, are versatile biomolecules. Functional groups in different amino acids endow these biomolecules with unique properties including self-assembly, ion-conducting, antioxidation, great affinity to exterior species, etc. Besides, protein and its subunit materials can not only work in solid forms but also in liquid forms when dissolved in solutions, making them more versatile to realize materials engineering via diverse approaches. In this review, it is aimed to offer a comprehensive understanding of the properties of proteins and their subunits, and research progress of using these versatile biomolecules to address the engineering issues of various rechargeable batteries, including alkali-ion batteries, lithium-sulfur batteries, metal-air batteries, and flow batteries. The state-of-the-art advances in electrode, electrolyte, separator, binder, catalyst, interphase modification, as well as recycling of rechargeable batteries are involved, and the impacts of biomolecules on electrochemical properties are particularly emphasized. Finally, perspectives on this interesting field are also provided.

A Water-Stable Cationic SIFSIX MOF for Luminescent Probing of Cr2 O7 2- via Single-Crystal to Single-Crystal Transformation

The sensing and monitoring of toxic oxo-anion contaminants in water are of significant importance to biological and environmental systems. A rare hydro-stable SIFSIX metal-organic framework, SiF6 @MOF-1, {[Cu(L)2 (H2 O)2 ]·(SiF6 )(H2 O)}n , with exchangeable SiF6 2- anion in its pore is strategically designed and synthesized, exhibiting selective detection of toxic Cr2 O7 2- oxo-anion in an aqueous medium having high sensitivity, selectivity, and recyclability through fluorescence quenching phenomena. More importantly, the recognition and ion exchange mechanism is unveiled through the rarely explored single-crystal-to-single crystal (SC-SC) fashion with well-resolved structures. A thorough SC-SC study with interfering anions (Cl- , F- , I- , NO3 - , HCO3 - , SO4 2- , SCN- , IO3 - ) revealed no such transformations to take place, as per line with quenching studies. Density functional theory calculations revealed that despite a lesser binding affinity, Cr2 O7 2- shows strong orbital mixing and large driving forces for electron transfer than SiF6 2- , and thus enlightens the fluorescence quenching mechanism. This work inaugurates the usage of a SIFSIX MOF toward sensing application domain under aqueous medium where hydrolytic stability is a prime concern for their plausible implementation as sensor materials.

MOF-Based Solid-State Proton Conductors Obtained by Intertwining Protic Ionic Liquid Polymers with MIL-101

Solid-state proton conductors based on the use of metal-organic framework (MOF) materials as proton exchange membranes are being investigated as alternatives to the current state of the art. This study reports a new family of proton conductors based on MIL-101 and protic ionic liquid polymers (PILPs) containing different anions. By first installing protic ionic liquid (PIL) monomers inside the hierarchical pores of a highly stable MOF, MIL-101, then carrying out polymerization in situ, a series of PILP@MIL-101 composites was synthesized. The resulting PILP@MIL-101 composites not only maintain the nanoporous cavities and water stability of MIL-101, but the intertwined PILPs provide a number of opportunities for much-improved proton transport compared to MIL-101. The PILP@MIL-101 composite with HSO4 - anions shows superprotonic conductivity (6.3 × 10-2  S cm-1 ) at 85 °C and 98% relative humidity. The mechanism of proton conduction is proposed. In addition, the structures of the PIL monomers were determined by single crystal X-ray analysis, which reveals many strong hydrogen bonding interactions with O/NH···O distances below 2.6 Å.

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 [Formula: see text] 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 [Formula: see text] 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 [Formula: see text]-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.

Syntheses and High Proton Conductivities of Two 3D Zr(IV)/Hf(IV)-MOFs from Furandicarboxylic Acid

With the gradual progress of research on proton-conducting metal-organic framework (MOFs), it has become a challenging task to find MOF materials that are easy to prepare and have low toxicity, high stability, and splendid proton conductivity. With the abovementioned objectives in mind, we selected the non-toxic organic ligand 2,5-furandicarboxylic acid and the low toxic quadrivalent metals zirconium(IV) or hafnium(IV) as starting materials and successfully obtained 2 three-dimensional porous MOFs, [M6O4(OH)4(FDC)4(OH)4(H2O)4] [M = ZrIV (1) and HfIV (2)], with ultrahigh water stability using a rapid and green synthesis approach. Their proton conductive ability is remarkable, thanks to the large number of Lewis acidic sites contained in their porous frameworks and the abundant H-bonding network, hydroxyl groups, as well as coordination and crystalline water molecules. The positive correlation of their proton conductivity with relative humidity (RH) and the temperature was observed. Notably, their optimized proton conductivities are 2.80 × 10-3 S·cm-1 of 1 and 3.38 × 10-3 S·cm-1 of 2 under 100 °C/98% RH, which are at the forefront of Zr(IV)/Hf(IV) MOFs with prominent proton conductivity. Logically, their framework features, nitrogen/water adsorption/desorption data, and activation energy values are integrated to deduce their proton conductivity and conducting mechanism differences.

Optimization of a lipase/reduced graphene oxide/metal-organic framework electrode using a central composite design-response surface methodology approach

Lipase has been gaining attention as the recognition element in electrochemical biosensors. Lipase immobilization is important to maintain its stability while providing excellent conductivity. In this study, a lipase electrochemical biosensor immobilized on a copper-centred metal-organic framework integrated with reduced graphene oxide (lipase/rGO/Cu-MOF) was synthesized by a facile method at room temperature. Response surface methodology (RSM) via central composite design (CCD) was used to optimize the synthesis parameters, which are rGO weight, ultrasonication time, and lipase concentration, to maximize the current response for the detection of p-nitrophenyl acetate (p-NPA). The results of the analysis of variance (ANOVA) showed that all three parameters were significant, while the interaction between the ultrasonication time and lipase concentration was the only significant interaction with a p-value of less than 0.05. The optimized electrode with parameters of 1 mg of rGO, 30 min ultrasonication time, and 30 mg mL-1 lipase exhibited the highest current response of 116.93 μA using cyclic voltammetry (CV) and had a residual standard error (RSE) of less than 2% in validation, indicating that the model is suitable to be used. It was characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FTIR), where the integration of the composite was observed. Immobilization using ultrasonication altered the lipase's secondary structure, but reduced its unorderly coils. The electrochemical and thermal analysis showed that the combination of Cu-MOF with rGO enhanced the electrochemical conductivity and thermostability.

Anhydrous Superprotonic Conductivity in the Zirconium Acid Triphosphate ZrH5 (PO4 )3

The development of solid-state proton conductors with high proton conductivity at low temperatures is crucial for the implementation of hydrogen-based technologies for portable and automotive applications. Here, we report on the discovery of a new crystalline metal acid triphosphate, ZrH₅ (PO₄ )₃ (ZP3), which exhibits record-high proton conductivity of 0.5-3.1×10^-2  S cm^-1 in the range 25-110 °C in anhydrous conditions. This is the highest anhydrous proton conductivity ever reported in a crystalline solid proton conductor in the range 25-110 °C. Superprotonic conductivity in ZP3 is enabled by extended defective frustrated hydrogen bond chains, where the protons are dynamically disordered over two oxygen centers. The high proton conductivity and stability in anhydrous conditions make ZP3 an excellent candidate for innovative applications in fuel cells without the need for complex water management systems, and in other energy technologies requiring fast proton transfer.

Construction of MOF@COF composite-based electrochemical aptasensor for detection of Staphylococcus aureus

In this work, a biological metal-organic framework@conductive covalent organic framework composite (bio-MOF@con-COF, denoted as Zn-Glu@PTBD-COF, here, Glu indicates L-glutamic acid, PT indicates 1,10-phenanthroline-2,9-dicarbaldehyde, and BD indicates benzene-1,4-diamine) was prepared and used as sensing material to fabricate aptasensor for trace detection of Staphylococcus aureus (SA). The Zn-Glu@PTBD-COF integrates the mesoporous structure and abundant defects of the MOF framework, the excellent conductivity of the COF framework, and high stability of the composite, providing abundant active sites to effectively anchor aptamers. As a result, the Zn-Glu@PTBD-COF-based aptasensor shows high sensitivity to detect SA via specific recognition between aptamer and SA, as well as the formation of aptamer-SA complex. Low detection limits of 2.0 and 1.0 CFU·mL^-1 are deduced from the electrochemical impedance spectroscopy and differential pulse voltammetry within a wide linear range of 10-10⁸ CFU·mL^-1 for SA, respectively. The Zn-Glu@PTBD-COF-based aptasensor also shows good selectivity, reproducibility, stability, regenerability, and applicability for real milk and honey samples. Therefore, the Zn-Glu@PTBD-COF-based aptasensor will be promising for fast screening of foodborne bacteria in food service industry. Zn-Glu@PTBD-COF composite was prepared and used as sensing material to fabricate aptasensor for trace detection of Staphylococcus aureus (SA). Low detection limits of 2.0 and 1.0 CFU·mL^-1 are deduced from the electrochemical impedance spectroscopy and differential pulse voltammetry within a wide linear range of 10-10⁸ CFU·mL^-1 for SA, respectively. The Zn-Glu@PTBD-COF-based aptasensor also shows good selectivity, reproducibility, stability, regenerability, and applicability for real milk and honey samples.

Two Dual-Function Zr/Hf-MOFs as High-Performance Proton Conductors and Amines Impedance Sensors

In the field of sensing, finding high-performance amine molecular sensors has always been a challenging topic. Here, two highly stable 3D MOFs DUT-67(Hf) and DUT-67(Zr) with large specific surface areas and hierarchical pore structures were conveniently synthesized by solvothermal reaction of ZrCl₄/HfCl₄ with a simple organic ligand, 2,5-thiophene dicarboxylic acid (H₂TDC) according to literature approach. By analyzing TGA data, it was found that the two MOFs have defects (unsaturated metal sites) that can interact with substrates (H₂O and volatile amine gas), which is conducive to proton transfer and amine compound identification. Further experiments showed that at 100 °C and 98% relative humidity (RH), the optimized proton conductivities of DUT-67(Zr) and DUT-67(Hf) can reach the high values of 2.98 × 10^-3 and 3.86 × 10^-3 S cm^-1, respectively. Moreover, the room temperature sensing characteristics of MOFs' to amine gases were evaluated at 68, 85 and 98% RHs, respectively. Impressively, the prepared MOFs-based sensors have the desired stability and higher sensitivity to amines. Under 68% RH, the detection limits of DUT-67(Zr) or DUT-67(Hf) for volatile amine gases were 0.5 (methylamine), 0.5 (dimethylamine) and 1 ppm (trimethylamine), and 0.5 (methylamine), 0.5 (dimethylamine) and 0.5 ppm (trimethylamine), respectively. As far as we know, this is the best performance of ammonia room temperature sensors in the past proton-conductive MOF sensors.

Zirconium-amino acid framework as a green phosphatase-like nanozyme for the selective detection of phosphate-containing drugs

The zirconium-amino acid framework MIP-202(Zr) was reported as a green phosphatase-like nanozyme for the first time. Moreover, its phosphatase-like activity can be inhibited by phosphate-containing drugs. Based on this finding, a universal fluorimetric strategy for sensing phosphate-containing drugs was developed. The detection limit was as low as 2 ng mL^-1 for the model drug alendronate sodium. This strategy exhibits excellent selectivity over other non-phosphate-containing drugs and will broaden the applications of phosphatase-like nanozymes in clinical pharmacy.

Metal-Organic Frameworks as Intelligent Drug Nanocarriers for Cancer Therapy

Metal-organic frameworks (MOFs) are crystalline porous materials with periodic network structures formed by self-assembly of metal ions and organic ligands. Attributed to their tunable composition and pore size, ultrahigh surface area (1000-7000 m2/g) and pore volume (1.04-4.40 cm3/g), easy surface modification, appropriate physiological stability, etc., MOFs have been widely used in biomedical applications in the last two decades, especially for the delivery of bioactive agents. In the initial stage, MOFs were widely used to load small molecule drugs with ultra-high doses. Whereafter, more recent work has focused on the load of biomacromolecules, such as nucleic acids and proteins. Over the past years, we have devoted extensive effort to investigate the function of MOF materials for bioactive agent delivery. MOFs can be used not only as an intelligent nanocarrier to deliver or protect bioactive agents but also as an activator for their release or activation in response to the different microenvironments. Altogether, this review details the current progress of MOF materials for bioactive agent delivery and looks into their future development.