Nanoscale Metal-organic Frameworks Research Articles

Tailoring Electronic Structure and Size of Ultrastable Metalated Metal–Organic Frameworks with Enhanced Electroconductivity for High‐Performance Supercapacitors

AbstractUtilization of metal–organic frameworks (MOFs) as electrodes for energy storage/conversion is challenging because of the low chemical stability and poor electrical conductivity of MOFs in electrolytes. A nanoscale MOF, Co0.24Ni0.76‐bpa‐200, possessing ultrahigh stability with uncommon semiconductor behavior (σ=4.2×10−3 S m−1) was fabricated. The MOF comprises a robust hydrophobic paddlewheel and an optimized Co/Ni ratio, with consequent control over MOF size and the degree of conjugation of the coligand. A DFT study revealed that appropriate Ni2+ doping reduces the activation energy of the system, thus providing a higher carrier concentration, and the strongly delocalized N‐donor ligand notably increases the metal–ligand orbital overlap to achieve efficient charge migration, leading to continuous through‐bond (‐CoNi‐N‐CoNi‐)∞ conduction paths. These structural features endow the MOF with a good cycling stability of 86.5 % (10 000 cycles) and a high specific capacitance of 1927.14 F g−1 among pristine MOF‐based electrodes.

Engineering Nanoscale Metal‐Organic Frameworks for Heterogeneous Catalysis

Metal‐organic frameworks (MOFs) are porous crystalline materials composed of metal ions (or clusters) and organic ligands. Targeted preparation of nanoscale MOFs has been successfully achieved through numerous synthetic methods and is beneficial to improve the utilization of catalytic sites. On one hand, the dynamic bonds and rich selection of both metal centers and organic molecules enable broadening the types and functions of MOFs, thus offering the basis for rational design of heterogeneous catalysts at the molecular level. On the other hand, the reversible nature of connections between metal centers and organic ligands brings serious challenges about its stability under harsh reaction conditions. To optimize the catalytic performance of MOFs, considerable efforts have been devoted to tune the chemical environment of active sites by introducing electronic or channel confinement effect as well as controlling their size growth at nanoscale for increasing the surface coordination unsaturated sites. In this review, the state‐of‐the‐art development of nanoscale MOFs is summarized and particular focus is placed on regulation strategies of catalytic sites. The authors also propose the current challenges, the problems awaiting to be solved and opportunities in the future.

Designed Eu(III)-functionalized nanoscale MOF probe based on fluorescence resonance energy transfer for the reversible sensing of trace Malachite green

An ingenious nanoscale fluorescent sensor derived from Eu3+-postfunctionalized MIL-53 (Al) (Eu3+@MIL-53 [Al]) was fabricated though a simple and effective approach. Malachite green (MG) effectively turned off the luminescence of Eu3+@MIL-53 (Al) via fluorescence resonance energy transfer (FRET), thus enabling MG sensing. The developed probe exhibited instantaneous reusability after being cleaned with deionized water. The fluorescence intensity, quenching efficiency, and crystal structure of the recoverable sensor after five recycling processes were unchanged compared with those of the original sample. Moreover, the potential mechanism of MG detection was revealed in detail. This work represents the first attempt to determine MG in aquaculture water and products by using metal–organic frameworks (MOFs). The Eu3+@MIL-53 (Al) probe proved to be a remarkable fluorescence probe for MG with high selectivity, sensitivity, and excellent regeneration capability. It provides a promising functional platform for the recognition of illegal MG addition to aquaculture water and products.

Nanomedicine-Based Strategies Assisting Photodynamic Therapy for Hypoxic Tumors: State-of-the-Art Approaches and Emerging Trends.

Since the first clinical cancer treatment in 1978, photodynamic therapy (PDT) technologies have been largely improved and approved for clinical usage in various cancers. Due to the oxygen-dependent nature, the application of PDT is still limited by hypoxia in tumor tissues. Thus, the development of effective strategies for manipulating hypoxia and improving the effectiveness of PDT is one of the most important area in PDT field. Recently, emerging nanotechnology has benefitted progress in many areas, including PDT. In this review, after briefly introducing the mechanisms of PDT and hypoxia, as well as basic knowledge about nanomedicines, we will discuss the state of the art of nanomedicine-based approaches for assisting PDT for treating hypoxic tumors, mainly based on oxygen replenishing strategies and the oxygen dependency diminishing strategies. Among these strategies, we will emphasize emerging trends about the use of nanoscale metal–organic framework (nMOF) materials and the combination of PDT with immunotherapy. We further discuss future perspectives and challenges associated with these trends in both the aspects of mechanism and clinical translation.

Versatile Nanoscale Metal-Organic Frameworks (nMOFs): An Emerging 3D Nanoplatform for Drug Delivery and Therapeutic Applications.

For decades, nanoscale metal-organic frameworks (nMOFs) have attracted extensive interest in biomedicine due to their distinct characteristics, including facile synthesis, porous interior, and tunable biocompatibility. With high porosity, versatile nMOFs allow for the facile encapsulation of various therapeutic agents with exceptionally high payloads. Constructed from metal ions and organic linkers through coordination bonds, nMOFs with plentiful functional groups enable the surface modification for active targeting and enhanced biocompatibility. This review outlines the up-to-date progresses on the exploration of nMOFs in the field of biomedicine. First, the classification and synthesis of nMOFs are discussed, followed by the concrete introduction of drug loading strategies of nMOFs and mechanisms of stimulation-responsive drug release. Second, the smart designs of the nMOFs-based platforms for anticancer and antibacterial treatment are summarized. Finally, the basic challenges faced by nMOFs research and the great potential of biomimetic nMOFs are presented. This review article affords an inspiring insight into the interdisciplinary research of nMOFs and their biomedical applications, which holds great expectation for their further clinical translation.

Tumor microenvironments self-activated nanoscale metal-organic frameworks for ferroptosis based cancer chemodynamic/photothermal/chemo therapy

Ferroptosis, as a newly discovered cell death form, has become an attractive target for precision cancer therapy. Several ferroptosis therapy strategies based on nanotechnology have been reported by either increasing intracellular iron levels or by inhibition of glutathione (GSH)-dependent lipid hydroperoxidase glutathione peroxidase 4 (GPX4). However, the strategy by simultaneous iron delivery and GPX4 inhibition has rarely been reported. Herein, novel tumor microenvironments (TME)-activated metal-organic frameworks involving Fe & Cu ions bridged by disulfide bonds with PEGylation (FCSP MOFs) were developed, which would be degraded specifically under the redox TME, simultaneously achieving GSH-depletion induced GPX4 inactivation and releasing Fe ions to produce ROS via Fenton reaction, therefore causing ferroptosis. More ROS could be generated by the acceleration of Fenton reaction due to the released Cu ions and the intrinsic photothermal capability of FCSP MOFs. The overexpressed GSH and H2O2 in TME could ensure the specific TME self-activated therapy. Better tumor therapeutic efficiency could be achieved by doxorubicin (DOX) loading since it can not only cause apoptosis, but also indirectly produce H2O2 to amplify Fenton reaction. Remarkable anti-tumor effect of obtained FCSP@DOX MOFs was verified via both in vitro and in vivo assays.

Nanocomposite Hydrogel of Pd@ZIF-8 and Laponite® : Size-Selective Hydrogenation Catalyst under Mild Conditions.

The composite hydrogel of a nanoscale metal-organic framework (NMOF) and nanoclay has emerged as a new soft-material with advanced properties and applications. Herein, we report a facile synthesis of a hydrogel nanocomposite by charge-assisted self-assembly of Pd@ZIF-8 nanoparticles with Laponite® nanoclay which coat the surface of Pd@ZIF-8 nanoparticles. Such surface coating significantly enhanced the thermal stability of the ZIF-8 compared to the pristine framework. Further, the Pd@ZIF-8+LP hydrogel nanocomposite shows better size-selective catalytic hydrogenation of olefins than Pd@ZIF-8 nanoparticles based on selective diffusion of the substrate.

Energy Efficient Ultrahigh Flux Separation of Oily Pollutants from Water with Superhydrophilic Nanoscale Metal–Organic Framework Architectures

AbstractThe rising demand for clean water for a growing and increasingly urban global population is one of the most urgent issues of our time. Here, we introduce the synthesis of a unique nanoscale architecture of pillar‐like Co‐CAT‐1 metal–organic framework (MOF) crystallites on gold‐coated woven stainless steel meshes with large, 50 μm apertures. These nanostructured mesh surfaces feature superhydrophilic and underwater superoleophobic wetting properties, allowing for gravity‐driven, highly efficient oil–water separation featuring water fluxes of up to nearly one million L m−2 h−1. Water physisorption experiments reveal the hydrophilic nature of Co‐CAT‐1 with a total water vapor uptake at room temperature of 470 cm3 g−1. Semiempirical molecular orbital calculations shed light on water affinity of the inner and outer pore surfaces. The MOF‐based membranes enable high separation efficiencies for a number of liquids tested, including the notorious water pollutant, crude oil, affording chemical oxygen demand (COD) concentrations below 25 mg L−1 of the effluent. Our results demonstrate the great impact of suitable nanoscale surface architectures as a means of encoding on‐surface extreme wetting properties, yielding energy‐efficient water‐selective large‐aperture membranes.

Energy Efficient Ultrahigh Flux Separation of Oily Pollutants from Water with Superhydrophilic Nanoscale Metal-Organic Framework Architectures.

The rising demand for clean water for a growing and increasingly urban global population is one of the most urgent issues of our time. Here, we introduce the synthesis of a unique nanoscale architecture of pillar‐like Co‐CAT‐1 metal–organic framework (MOF) crystallites on gold‐coated woven stainless steel meshes with large, 50 μm apertures. These nanostructured mesh surfaces feature superhydrophilic and underwater superoleophobic wetting properties, allowing for gravity‐driven, highly efficient oil–water separation featuring water fluxes of up to nearly one million L m−2 h−1. Water physisorption experiments reveal the hydrophilic nature of Co‐CAT‐1 with a total water vapor uptake at room temperature of 470 cm3 g−1. Semiempirical molecular orbital calculations shed light on water affinity of the inner and outer pore surfaces. The MOF‐based membranes enable high separation efficiencies for a number of liquids tested, including the notorious water pollutant, crude oil, affording chemical oxygen demand (COD) concentrations below 25 mg L−1 of the effluent. Our results demonstrate the great impact of suitable nanoscale surface architectures as a means of encoding on‐surface extreme wetting properties, yielding energy‐efficient water‐selective large‐aperture membranes.

Nanoscale metal-organic frameworks for tumor phototherapy.

Metal-Organic Frameworks (MOFs) are constructed from metal ions/cluster nodes and functional organic ligands through coordination bonds. Owing to the advantages of diverse synthetic methods, easy modification after synthesis, large adsorption capacity for heavy metals, and short equilibrium time, considerable attention has recently been paid to MOFs for tumor phototherapy. Through rational tuning of metal ions and ligands, MOFs present abundant properties for various applications. Light-triggered phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is an emerging cancer treatment approach. Nanosized MOFs can be applied as phototherapeutic agents to accomplish phototherapy with excellent phototherapeutic efficacy. This review outlines the latest advances in the field of phototherapy with various metal ion-based MOFs.

Versatile labeling of multiple radionuclides onto a nanoscale metal-organic framework for tumor imaging and radioisotope therapy.

Radionuclides for cancer theranostic have confronted problems such as limitation in real-time visualization and unsatisfactory therapeutic effect sacrificed by the nonspecific distribution. Nanoscale metal-organic frameworks (nMOFs) have been widely used in biomedical applications including cancer imaging and drug delivery. However, there have been rare reports utilizing nMOFs as a single nanoplatform to label various radionuclides for tumor imaging and radioisotope therapy (RIT). In this work, we developed polyethylene glycol (PEG) modified zirconium-based nMOFs (PCN-224) with favorable size, water solubility and biocompatibility. Interestingly, without the help of chelating agents, metal radionuclides (technetium-99 m/99mTc, lutetium-177/177Lu) could be efficiently labeled onto nMOFs via chelating with the porphyrin structure and iodine-125 (125I) via chemical substitution of hydrogen in the benzene ring. The radionuclide-labeled PCN-PEG nanoparticles all exhibit excellent radiolabeling stability in different solutions. In accordance with the fluorescence imaging of mice injected with PCN-PEG, SPECT/CT imaging illustrates strong tumor accumulation of 99mTc-PCN-PEG. Moreover, 177Lu-PCN-PEG significantly inhibited the growth of tumor without inducing any perceptible toxicity to the treated mice. Hence, the radionuclide-delivery nanoplatform based on nMOFs would provide more opportunities for precise tumor theranostics and expand the biomedical applications of MOF nanomaterials.

Nanoscale metal–organic framework composites for phototherapy and synergistic therapy of cancer

This review mainly discusses and summarizes the advancement of MOF-based nanocomposites as a therapeutic platform for cancer phototherapy or synergistic phototherapy within the last five years.

Applications of nanoscale metal–organic frameworks as imaging agents in biology and medicine

Nanoscale metal-organic frameworks (NMOFs) are an interesting and unique class of hybrid porous materials constructed by the self-assembly of metal ions/clusters with organic linkers. The high storage capacities, facile synthesis, easy surface functionalization, diverse compositions and excellent biocompatibilities of NMOFs have made them promising agents for theranostic applications. By combination of a large variety of metal ions and organic ligands, and incorporation of desired molecular functionalities including imaging modalities and therapeutic molecules, diverse MOF structures with versatile functionalities can be obtained and utilized in biomedical imaging and drug delivery. In recent years, NMOFs have attracted great interest as imaging agents in optical imaging (OI), magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET) and photoacoustic imaging (PAI). Furthermore, the significant porosity of MOFs allows them to be loaded with multiple imaging agents and therapeutics simultaneously and applied for multimodal imaging and therapy as a single entity. In this review, which is intended as an introduction to the use of MOFs in biomedical imaging for a reader entering the subject, we summarize the up-to-date progress of NMOFs as bioimaging agents, giving (i) a broad perspective of the varying imaging techniques that MOFs can enable, (ii) the different routes to manufacturing functionalised MOF nanoparticles and hybrids, and (iii) the integration of imaging with differing therapeutic techniques. The current challenges and perspectives of NMOFs for their further clinical translation are also highlighted and discussed.

Recent Progress of Nanoscale Metal-Organic Frameworks in Synthesis and Battery Applications.

As one type of promising inorganic–organic hybrid crystal material, metal‐organic frameworks (MOFs) have attracted widespread attention in many potential fields, particularly in energy storage and conversion. Recently, effective strategies have been developed to construct uniform nanoscale MOFs (NMOFs), which not only retain inherent advantages of MOFs but also develop some improved superiorities, including shorter diffusion pathway for guest transportation and more accessible active sites for surface adsorption and reaction. Additonally, their nanometer size provides more opportunity for post‐functionalization and hybridization. In this review, recent progress on the preparation of NMOFs is summarized, primarily through bottom‐up strategies including reaction parameter‐ and coordination‐assisted synthesis, and top‐down strategies such as liquid exfoliation and salt‐template confinement. Additionally, recent applications of NMOFs in batteries as electrodes, separators, and electrolytes is discussed. Finally, some important issues concerning the fabrication and application are emphasized, which should be paid attention in future.

Multiple adsorption properties of aptamers on metal-organic frameworks for nucleic acid assay

Enrichment and detection of circulating free nucleic acids in biological samples have gained great attention for disease diagnosis or prognostic evaluation. Nanoscale metal-organic frameworks (NMOFs) have been used for aptamer-based nucleic acid sensing. In this work, different NMOFs, including ZIF-8, MIL-88, MIL-100, MIL-101, as well as Eu-TDA and Tb-TDA [prepared by the coordination of 2,2′-thiodiacetic acid (TDA) and Eu3+ or Tb3+], were investigated in nucleic acid sensing by employing their aptamer adsorption ability and fluorescence quenching capacity for the labeled dyes. Two types of dye aptamer, FAM-labeled aptamer (FAM-Ap) and TexasRedaptamer (TexasRed-Ap) were designed, and their adsorption properties on NMOFs-were compared. It was found that the TexasRed-Ap can be well used for nucleic acid (miR-21) extraction and sensing by linking with a pH-responsive nucleotide chain (TexasRed-Ap-pH) or with an additional random chain ssDNA-1′ (TexasRed-Ap-a). After interacted with the target miR-21 in biosamples, the TexasRed-dsDNA + NMOFs composites can be collected, and the formed TexasRed-dsDNA can be released by changing pH value or addition of ssDNA-1, which is matched with ssDNA-1′. A linear relationship from 0.1 to 200 pM for miR-21 detection was obtained. The results show that the NMOFs can be used as promising platforms for nucleic acid extraction and fluorescent sensing.

Fucoidan-coated nanoparticles target radiation-induced P-selectin to enhance chemoradiotherapy in murine colorectal cancer.

Colorectal cancer (CRC) is a leading cause of cancer-related death for both men and women, highlighting the need for new treatment strategies. Advanced disease is often treated with a combination of radiation and cytotoxic agents, such as DNA damage repair inhibitors and DNA damaging agents. To optimize the therapeutic window of these multimodal therapies, advanced nanomaterials have been investigated to deliver sensitizing agents or enhance local radiation dose deposition. In this study, we demonstrate the feasibility of employing an inflammation targeting nanoscale metal-organic framework (nMOF) platform to enhance CRC treatment. This novel formulation incorporates a fucoidan surface coating to preferentially target P-selectin, which is over-expressed or translocated in irradiated tumors. Using this radiation stimulated delivery strategy, a combination PARP inhibitor (talazoparib) and chemotherapeutic (temozolomide) drug-loaded hafnium and 1,4-dicarboxybenzene (Hf-BDC) nMOF was evaluated both in vitro and in vivo. Significantly, these drug-loaded P-selectin targeted nMOFs (TT@Hf-BDC-Fuco) show improved tumoral accumulation over multiple controls and subsequently enhanced therapeutic effects. The integrated radiation and nanoformulation treatment demonstrated improved tumor control (reduced volume, density, and growth rate) and increased survival in a syngeneic CRC mouse model. Overall, the data from this study support the continued investigation of radiation-priming for targeted drug delivery and further consideration of nanomedicine strategies in the clinical management of advanced CRC.

In Vivo Uranium Sequestration using a Nanoscale Metal–Organic Framework

AbstractAn agent for actinide sequestration with fast uranium uptake kinetics and efficient in vivo uranium removal using a nanoscale metal–organic framework (nano‐MOF) is proposed. UiO‐66 nanoparticles post‐synthetically functionalized with carboxyl groups, UiO‐66‐(COOH)4‐180, exhibit the fastest uranium uptake kinetics reported with more than 65 % of uranyl in fetal bovine serum (FBS) removed within 5 min. Moreover, the in vivo bio‐distribution studies show that the material partially accumulates in kidneys and femurs where uranium mainly deposits facilitating the in vivo sequestration of uranium. The results of the in vivo uranium decorporation assays with mice show that UiO‐66‐(COOH)4‐180 could successfully reduce the amounts of uranyl deposited in kidneys and femurs by up to 55.4 % and 36.5 %, respectively, and is significantly more efficient than the commercial actinide decorporation agent, ZnNa3‐DTPA.

In Vivo Uranium Sequestration using a Nanoscale Metal-Organic Framework.

An agent for actinide sequestration with fast uranium uptake kinetics and efficient in vivo uranium removal using a nanoscale metal-organic framework (nano-MOF) is proposed. UiO-66 nanoparticles post-synthetically functionalized with carboxyl groups, UiO-66-(COOH)4 -180, exhibit the fastest uranium uptake kinetics reported with more than 65 % of uranyl in fetal bovine serum (FBS) removed within 5 min. Moreover, the in vivo bio-distribution studies show that the material partially accumulates in kidneys and femurs where uranium mainly deposits facilitating the in vivo sequestration of uranium. The results of the in vivo uranium decorporation assays with mice show that UiO-66-(COOH)4 -180 could successfully reduce the amounts of uranyl deposited in kidneys and femurs by up to 55.4 % and 36.5 %, respectively, and is significantly more efficient than the commercial actinide decorporation agent, ZnNa3 -DTPA.

E. coli@UiO-67 composites as a recyclable adsorbent for bisphenol A removal

E. coli@UiO-67 composites were obtained using an effective and simple self-assembly method. The composites showed unique properties as a remarkable and recyclable adsorbent for the efficient removal of bisphenol A (BPA) from water with a high adsorption capacity (402.930 mg g−1). The increase in pore size is a key factor why E. coli@UiO-67 composites maintained high capacity. The reason might be due to that the composites with large pore sizes and defects could effectively improve mass transport and active molecular metal sites. The adsorption of BPA is a chemisorption process due to the Zr–OH groups in UiO-67 exhibit affinity toward BPA molecules, π–π interaction, and electrostatic attraction. The adsorption efficiency remained at 82.5% after 15 cycles without any remarkable changes in the PXRD patterns of E. coli@UiO-67. Moreover, the use of microorganism-loading MOFs could reduce the cost to at least 50% and minimize secondary pollution through nanoscale MOFs usage reduction. The developed composites have advantages, including low-cost, high adsorption capacity, easy to be separated and regenerated from aqueous solution, a large number of cycles, short adsorption equilibrium time, and stability, showing excellent application prospects. The presented strategy would be a potentially promising way to produce novel MOFs-based adsorbents with high-performance to control environmental pollution from wastewater.

Environmental and intercellular Pb2+ ions determination based on encapsulated DNAzyme in nanoscale metal-organic frameworks.

With the merits of low cost, simple synthesis procedure, and high affinity for metal ions, deoxyribozyme (DNAzyme) have played important roles in metal ions detection. However, the intracellular applications of DNAzyme are limited because of enzymatic degradation and inefficient cellular uptake. To address these problems, GR-5 as model DNAzyme was encapsulatedinto zeolitic imidazolate frameworks-8 (ZIF-8) nanoparticles by biomimetic mineralization. The positively charged ZIF-8 with high DNAzyme loading capacity retained their ability to enter cells. Compared with free DNAzyme, the biomimetic mineralization synthesis method has greatly improved the stability of pristine DNAzyme. The as-synthesized DNAzyme@ZIF-8 composite exhibited good stability resisting DNase I, and was used as a sensitive fluorescent nanoprobe for Pb2+ determination and successfully achieved selective and sensitive determination for Pb2+ at λex/λem = 494/522nm in real samples. The linear range for the determination of Pb2+ is 50 to 500nM. Moreover, the highly active DNAzyme delivered by ZIF-8 allows noninvasive imaging of Pb2+ measurement in living cells. This strategy will extend the suitability of functional nucleic acids forin vitro and in vivo bioanalysis and bioimaging. Graphical abstract.