Metal-Organic Framework Nanoparticles

Rapid and Low-Cost Electrochemical Synthesis of UiO-66-NH2 with Enhanced Fluorescence Detection Performance

Rapid and low-cost synthesis of metal-organic frameworks (MOFs) are very meaningful for their future practical application. In the present study, a Zr-based ultrastable MOF, UiO-66-NH₂, was successfully synthesized by electrochemical method using metal Zr as the metal source at room temperature and atmospheric pressure. The effects of the reaction conditions, including the ratio of solvent (electrolyte), the applied voltage and different reaction time, on the crystallinity, morphology, and synthesis rate of the product were fully investigated. The results confirm that electrochemically synthesized UiO-66-NH₂ under the optimized condition possesses apparent merits such as high crystallinity, uniform morphology and high porosity. Moreover, the electrochemical synthesis method of UiO-66-NH₂ is promising for the large-scale and economical synthesis of nanoscale product to gramme degree. Interestingly, the resulting UiO-66-NH₂ synthesized by this electrochemical method exhibits more excellent performance for the fluorescence detection of Fe³⁺ ions in water (detection limit of 10^-8 mol/L) than that of the material prepared by solvothermal method.

Cactus-Inspired Bimetallic Metal-Organic Framework-Derived 1D-2D Hierarchical Co/N-Decorated Carbon Architecture toward Enhanced Electromagnetic Wave Absorbing Performance

Metal-organic framework (MOF)-derived magnetic metal/carbon nanocomposites have shown tremendous potential for lightweight electromagnetic wave (EMW) absorption. However, it is a challenge but highly significant to design and construct mixed-dimensional hierarchical architectures with synergistically integrated characteristics from individual MOFs for advancing the EMW absorption performance. Inspired by the structure of cactus, a novel hierarchical one-dimensional (1D)-two-dimensional (2D) mixed-dimensional Co/N-decorated carbon architecture comprising carbon nanotubes grafted on carbon flakes (abbreviated as CoNC/CNTs) has been fabricated by the pyrolysis of bimetallic CoZn-ZIF-L. The CoNC/CNTs integrate the advantages of 1D nanotubes for the extra polarization of EMW and 2D nanoflakes with an interconnected porous structure for multiple reflection losses of EMW and optimization of impedance matching. The resultant CoNC/CNTs demonstrate excellent EMW absorbing performance. For the optimal EMW absorbing material of CoNC/CNT-3/1, minimum reflection loss reaches -44.6 dB at 5.20 GHz with a low filler loading of 15 wt %. Moreover, the largest effective bandwidth range achieves 4.5 GHz with a thickness of 1.5 mm and a filled ratio of 20 wt %. These findings indicate that such a mixed 1D-2D hierarchical architecture synergistically enhances EMW absorbing performance. This work sheds light on the rational design of a mixed-dimensional carbon architecture derived from MOFs for desirable functionalities.

Topology and porosity control of metal-organic frameworks through linker functionalization

Tetratopic organic linkers have been extensively used in Zr-based metal-organic frameworks (MOFs) where diverse topologies have been observed. Achieving meticulous control over the topologies to tune the pore sizes and shapes of the resulting materials, however, remains a great challenge. Herein, by introducing substituents to the backbone of tetratopic linkers to affect the linker conformation, phase-pure Zr-MOFs with different topologies and porosity were successfully obtained under the same synthetic conditions. The conversion of CO2 to valuable cyclic carbonates is a promising route for the mitigation of the greenhouse gas. Owing to the presence of substrate accessible Lewis acidic Zr(iv) sites in the 8-connected Zr6 nodes, the Zr-MOFs in this study have been investigated as heterogenous acid catalysts for CO2 cycloaddition to styrene oxide. The MOFs exhibited drastically different catalytic activities depending on their distinct pore structures. Compared to previously reported MOF materials, a superior catalytic activity was observed with the mesoporous NU-1008, giving an almost 100% conversion under mild conditions.

Metal-Organic Framework-Based Stimuli-Responsive Systems for Drug Delivery

With the rapid development of nanotechnology, stimuli-responsive nanomaterials have provided an alternative for designing controllable drug delivery systems due to their spatiotemporally controllable properties. As a new type of porous material, metal-organic frameworks (MOFs) have been widely used in biomedical applications, especially drug delivery systems, owing to their tunable pore size, high surface area and pore volume, and easy surface modification. Here, recent progress in MOF-based stimuli-responsive systems is presented, including pH-, magnetic-, ion-, temperature-, pressure-, light-, humidity-, redox-, and multiple stimuli-responsive systems for the delivery of anticancer drugs. The remaining challenges and suggestions for future directions for the rational design of MOF-based nanomedicines are also discussed.

A Cu-Doped ZIF-8 metal organic framework as a heterogeneous solid catalyst for aerobic oxidation of benzylic hydrocarbons

Cu(ii) ions doped into ZIF-8 MOFs are shown to activate C–H bonds in benzylic hydrocarbons to their corresponding alcohol/ketone products.

Colloid-assisted growth of metal–organic framework nanoparticles

A new colloid-assisted approach is introduced to synthesize metal–organic framework (MOF) nanoparticles.

Recent advances in nanomaterial-based synergistic combination cancer immunotherapy

This review aims to summarize various synergistic combination cancer immunotherapy strategies based on nanomaterials.

Tailoring the photoluminescence of atomically precise nanoclusters

Due to their atomically precise structures and intriguing chemical/physical properties, metal nanoclusters are an emerging class of modular nanomaterials. Photo-luminescence (PL) is one of their most fascinating properties, due to the plethora of promising PL-based applications, such as chemical sensing, bio-imaging, cell labeling, phototherapy, drug delivery, and so on. However, the PL of most current nanoclusters is still unsatisfactory-the PL quantum yield (QY) is relatively low (generally lower than 20%), the emission lifetimes are generally in the nanosecond range, and the emitted color is always red (emission wavelengths of above 630 nm). To address these shortcomings, several strategies have been adopted, and are reviewed herein: capped-ligand engineering, metallic kernel alloying, aggregation-induced emission, self-assembly of nanocluster building blocks into cluster-based networks, and adjustments on external environment factors. We further review promising applications of these fluorescent nanoclusters, with particular focus on their potential to impact the fields of chemical sensing, bio-imaging, and bio-labeling. Finally, scope for improvements and future perspectives of these novel nanomaterials are highlighted as well. Our intended audience is the broader scientific community interested in the fluorescence of metal nanoclusters, and our review hopefully opens up new horizons for these scientists to manipulate PL properties of nanoclusters. This review is based on publications available up to December 2018.

Functionalized Ordered Mesoporous Silicas (MCM-41): Synthesis and Applications in Catalysis

Mesoporous silica sieves are among the most studied nano-objects due to their stable pore structure and easy preparation. In particular, MCM-41 have attracted increasing research attention due to their chemical versatility. This review focuses on the synthesis and regioselective functionalization of MCM-41 to prepare catalytic systems. The topics covered are: mono and di-functionalized MCM-41 as basic and acid catalysts, catalysts based on metallic complexes and heteropolyacids supported onto MCM-41, metallic nanoparticles embed onto functionalized MCM-41 and magnetic MCM-41 for catalytic purposes.

ZD2-Engineered Gold Nanostar@Metal-Organic Framework Nanoprobes for T1 -Weighted Magnetic Resonance Imaging and Photothermal Therapy Specifically Toward Triple-Negative Breast Cancer

Compared with other subtypes of breast cancer, triple-negative breast cancer (TNBC) is seriously threatening to human life. Therefore, it is a matter of urgency to develop multifunctional nanoprobes for visualized theranostics of TNBC, achieving specific targeting toward only TNBC, but not other subtypes. Nanoscale metal-organic frameworks (MOFs) show important potential in visualized theranostics of tumors, but it is critical to synthesize well-defined core-shell MOF-based nanocomposites by encapsulating a single nanoparticle within MOF. In this study, a TNBC-targeted peptide (ZD2)-engineered, and a single gold nanostar (AuNS) coated within MIL-101-NH₂ (Fe) by coating MOF with four cycles, obtain well-defined core-shell AuNS@MOF-ZD2 nanocomposites, which are expected to achieve T₁ -weighted magnetic resonance imaging and photothermal therapy (PTT) specifically targeting toward TNBC. The prepared AuNS@MOF-ZD2 nanocomposites possess good biocompatibility, efficient T₁ -weighted magnetic resonance (MR) relaxivity and stable photothermal conversion ability with an efficiency of 40.5%. The in vitro and in vivo characterizations prove their performances of T₁ -weighted MR and PTT with a low power density of 808 nm laser, achieving excellent theranostic efficacy in TNBC. Importantly, it is demonstrated that the prepared AuNS@MOF-ZD2 nanoprobes can specifically target TNBC cells (MDA-MB-231), but not other subtypes of breast cancer cells (MDA-MB-435, MDA-MB-468, and MCF-7), indicating their promising application in visualized theranostics of breast cancers with molecular classification.

Recent Trends in Covalent and Metal Organic Frameworks for Biomedical Applications

Materials science has seen a great deal of advancement and development. The discovery of new types of materials sparked the study of their properties followed by applications ranging from separation, catalysis, optoelectronics, sensing, drug delivery and biomedicine, and many other uses in different fields of science. Metal organic frameworks (MOFs) and covalent organic frameworks (COFs) are a relatively new type of materials with high surface areas and permanent porosity that show great promise for such applications. The current study aims at presenting the recent work achieved in COFs and MOFs for biomedical applications, and to examine some challenges and future directions which the field may take. The paper herein surveys their synthesis, and their use as Drug Delivery Systems (DDS), in non-drug delivery therapeutics and for biosensing and diagnostics.

A Novel Tb@Sr-MOF as Self-Calibrating Luminescent Sensor for Nutritional Antioxidant

Sesamol, is well-known antioxidant and can reduce the rate of oxidation and prolong expiration date. It is also potentially antimutagenic and antihepatotoxic, the detection of sesamol is important and remains a huge challenge. Herein, a new 3D alkaline earth Sr metal organic framework [Sr(BDC)DMACH₂O]n (BDC = benzene-1,4-dicarboxylate; DMAC = N,N-dimethylacetamide) is synthesized and a probe based on Tb3+ functionalized Sr-MOF. The Tb(3+)@Sr-MOF showed good luminescence and thermal property. Due to the energy competition between sesamol and ligand, the luminescence intensity of sesamol increases meantime luminescence intensity of Tb3+ decreases, the ratio of the emission intensities (I344/I545) linearly increases with sesamol in concentrations ranging from 1 × 10-7 to 8 × 10-4 M. Furthermore, the fluorescence-detected circular test shows that the composite Tb(3+)@Sr-MOF can serve as ratiometric sensor for sensing of sesamol. This is the first example for self-calibrated detecting sesamol based on metal-organic framework (MOF).

Surface-Functionalization of Zr-Fumarate MOF for Selective Cytotoxicity and Immune System Compatibility in Nanoscale Drug Delivery

Metal-organic frameworks (MOFs), network structures wherein metal ions or clusters link organic ligands into porous materials, are being actively researched as nanoscale drug delivery devices as they offer tunable structures with high cargo loading that can easily be further functionalized for targeting and enhanced physiological stability. The excellent biocompatibility of Zr has meant that its MOFs are among the most studied to date, in particular the archetypal Zr terephthalate UiO-66. In contrast, the isoreticular analog linked by fumarate (Zr-fum) has received little attention, despite the endogenous linker being part of the Krebs cycle. Herein, we report a comprehensive study of Zr-fum in the context of drug delivery. Reducing particle size is shown to increase uptake by cancer cells while reducing internalization by macrophages, immune system cells that remove foreign objects from the bloodstream. Zr-fum is compatible with defect loading of the drug dichloroacetate (DCA) as well as surface modification during synthesis, through coordination modulation and postsynthetically. DCA-loaded, PEGylated Zr-fum shows selective in vitro cytotoxicity toward HeLa and MCF-7 cancer cells, likely as a consequence of its enhanced caveolae-mediated endocytosis compared to uncoated precursors, and it is well tolerated by HEK293 kidney cells, J774 macrophages, and human peripheral blood lymphocytes. Compared to UiO-66, Zr-fum is more efficient at transporting the drug mimic calcein into HeLa cells, and DCA-loaded, PEGylated Zr-fum is more effective at reducing HeLa and MCF-7 cell proliferation than the analogous UiO-66 sample. In vitro examination of immune system response shows that Zr-fum samples induce less reactive oxygen species than UiO-66 analogs, possibly as a consequence of the linker being endogenous, and do not activate the C3 and C4 complement cascade pathways, suggesting that Zr-fum can avoid phagocytic activation. The results show that Zr-fum is an attractive alternative to UiO-66 for nanoscale drug delivery, and that a wide range of in vitro experiments is available to greatly inform the design of drug delivery systems prior to early stage animal studies.

Two-dimensional metal–organic framework nanosheets: synthesis and applications

Synthesis and applications of two-dimensional metal–organic framework nanosheets and their composites are summarized.

A flexible metal–organic framework with adaptive pores for high column-capacity gas chromatographic separation

A new zinc pyrazolyl-carboxylate framework with multi-mode and adaptive flexibility has been synthesized for efficient gas chromatographic separations.