Doped Metal Organic Framework Research Articles

Enhancement of Luminescence from Lanthanide Metal–Organic Frameworks by Ytterbium and Calcium Doping: Application to Photonic Barcodes and Fingerprint Detection

AbstractEmission from metal–organic frameworks (MOFs) made from Eu3+ and 1,3,5‐benzenetricarboxylic acid (BTC) is enhanced eightfold by doping with Y3+ and Ca2+ ions. The Ca2+ ions are shown to substitute into the MOFs, and the MOFs structure is shown to be retained at high Y3+ doping levels. The emission enhancement is shown to be associated with variations in the local electric field at the Eu3+ centers in the MOFs. Calculations indicate that the HOMO and LUMO levels vary considerably with both Y3+ doping and with low‐level Ca2+ doping. These then modulates Eu3+ concentration quenching, ligand‐metal energy transfer processes, and the local electric field at the Eu3+ centers, qualitatively accounting for the primary observed features. For UV excitation (250, 295, and 393 nm, respectively), the greatest emission enhancement comes from the doped MOFs with 10% Eu3+, 89% Y3+, and 1% Ca2+. In a photonic barcode application, the doped MOFs are shown to facilitate increased information storage density, and in a fingerprinting application, they are displayed to lead to higher photostability and reduced materials demand.

Emerging Doped Metal–Organic Frameworks: Recent Progress in Synthesis, Applications, and First‐Principles Calculations

AbstractMetal–organic frameworks (MOFs) are crystalline porous materials with a long‐range ordered structure and excellent specific surface area and have found a wide range of applications in diverse fields, such as catalysis, energy storage, sensing, and biomedicine. However, their poor electrical conductivity and chemical stability, low capacity, and weak adhesion to substrates have greatly limited their performance. Doping has emerged as a unique strategy to mitigate the issues. In this review, the concept, classification, and characterization methods of doped MOFs are first introduced, and recent progress in the synthesis and applications of doped MOFs, as well as the rapid advancements and applications of first‐principles calculations based on the density functional theory (DFT) in unraveling the mechanistic origin of the enhanced performance are summarized. Finally, a perspective is included to highlight the key challenges in doping MOF materials and an outlook is provided on future research directions.

Au doped metal organic frameworks as di-functional photocatalysts for clearing organics in wastewater

Along with the development of productive forces, the use of organic compounds including diversified dyes and multiple drugs has become more and more commonly, resulting in the accelerating water contamination. Herein in this paper, Au doped PCN 224 are designed as bi-functional wastewater treatment agents to absorb and decompose organics molecules efficiently under light irradiation. After inserted with Au, the PCN 224 nanoparticles, which is kind of porous, stable and photosensitive metal-organic framework, show enhanced photodegradeability. Because the Au inserted could inhibit the re-combination of electrons and holes by absorbing photo-electrons; decrease the nanoparticles’ band gap, and finally produce much more free radicals. In the meanwhile, due to the lower binding energy between S and Au, the Au modified PCN 224 perform better in absorbing organic compounds consisted of S contained heterocyclic ring (such as methylene blue). This work provides new insights into the precious design of materials in clearing organic compounds.

Constructing iron-group doped metal–organic framework films on hematite photoanodes for efficient solar water splitting

Constructing iron-group doped metal–organic framework films on hematite photoanodes for efficient solar water splitting

Determination of active constituents in kombucha fermentation broth using nano-composite colorimetric sensor based on selected volatile markers determined by GC–MS

Herein, a nano-composite colorimetric sensor array (Nano-CSA) coupled with near infrared (NIR) spectroscopy was developed for the determination of active constituents. Sixty-seven volatile compounds of seven chemical groups were determined as markers in the kombucha broth by headspace-solid phase microextraction- gas chromatography-mass spectrometry (HS-SPME-GC–MS). A nano-CSA composed of chemically responsive dyes doped metal–organic frameworks (MOF) was fabricated to obtain sensitive interaction with different volatile markers. Kombucha broth samples with different fermentation times were separated using chemometric methods Compared to these partial least squares (PLS) analyses, competitive adaptive reweighted sampling-PLS (CARS-PLS) performed optimally for the detection of tea polysaccharides (TPSs) with a prediction set (Rp) correlation coefficient of 0.9007. Despite the better performance of the CARS-PLS towards tea polyphenols (TPPs) with a Rp of 0.9144, the novel nano-CSA-NIRs provides the basis for the optimal results and a reliable system to estimate the chemical and physical properties of tea fermentation broth.

A novel doped metal–organic skeleton MnDUT-52 as a sorbent for dispersive solid phase extraction of diphenyl ether herbicides in the water environment

A manganese doped metal–organic framework composite (MnDUT-52) was fabricated by a facile solvothermal method and applied as an adsorbent for dispersive solid phase extraction (DSPE) of trace diphenyl ether herbicides (Des) in water samples. The doped material exhibited large surface area (527.3 m2/g) and a higher zeta potential (43.2 mV) compared with its precursor (8.57 mV). And the quantitative parameters affecting the DSPE process (i.e., adsorbent amount, adsorption time, pH, ionic strength, desorption solvent and desorption volume) were optimized in detail. Under the optimal conditions, MnDUT-52 exhibited good reusability (6 times reuse, RSDs ≤ 5.8 %). Notably, the conjugation, hydrophobic and electrostatic interactions contributed to the good adsorption of Des by MnDUT-52. Finally, a method coupled with high-performance liquid chromatography-ultraviolet (HPLC-UV) was developed. It provided wide linear range (0.2–300 ng/mL), low detection limits (0.06–0.10 ng/mL) and extraction recovery (82.4–102.5 %). The developed method was successfully applied for the fast and sensitive determination of Des in water samples.

Pebax mixed matrix membrane with bimetallic CeZr-MOFs to enhance CO2 separation

Amine-functionalized and metal doped metal–organic frameworks (MOFs) will enable further enhancement of CO2 adsorption, which holds great promise in mixed matrix membranes (MMMs) for CO2/N2 separation. Four kinds of UiO66 with different sizes have been successfully fabricated by introduction of Ce and/or amino groups in UiO66. The influence of Ce doping on the UiO66 is greatly related to the ligand. Compared with ZrUiO66, the CeZrUiO66 has bigger particle size, lower BET specific surface area and pore volume and a worse CO2 adsorption capacity. Interestingly, the tendency of Ce-doped ZrUiO66-NH2 is contrary to the aforementioned. In particular, bimetallic CeZrUiO66-NH2 has an ultramicroporous structure, small particle size, rich crystal defect, superb CO2 capture capacity and high CO2/N2 adsorption selectivity, suggesting that the simultaneous introduction of Ce and amino groups is conducive to the enhancement of CO2 separation. The intrinsic ultramicroporous structure of CeZrUiO66-NH2 not only offers fast and low resistance transport channels for CO2, but also supplies more sites for CO2 adsorption owning to the doping of Ce and the amino groups. As a result, Pebax/CeZrUiO66-NH2 (3 wt%) MMMs show the CO2 permeability of 100.7 Barrer and the CO2/N2 ideal selectivity of 76.4, which is close to Robeson upper bound from 2008. Meanwhile, the Pebax/CeZrUiO66-NH2 (3 wt%) MMMs present relatively good pressure resistance, which would be advantageous in terms of industrial application.

Heteroatom inducing local geometrical configuration transformation of metallic oxygen clusters in metal hydroxide-organic frameworks with optimized hydrogen evolution performance

Various heteroatom doped metal organic frameworks (MOFs) and MOFs derived materials with high activity are designed as electrochemical water splitting catalysts. However, local geometrical configuration transformation or local structure distortion on account of heteroatom doping are usually neglected. Herein, this work firstly investigated local structure transformation of metallic oxygen clusters to β-Ni(OH)2-like geometrical configuration (edge-shared octahedrons) in heteroatom (Ru, Cr, Sn and Ce) doped nickel based metal hydroxide-organic frameworks (MHOFs). The transformation process, atomic/electronic structure and composition are investigated via spectroscopy methods such as X-ray absorption structure spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. Hereinto, Ru doped Ni-MHOFs with high local geometrical configuration transformation as a representative one was deeply studied to reveal hydrogen evolution reaction properties. Density functional theory calculations provided a deep understanding of the effect of organic linker defect on local structure and descriptor of p-band center of O. This work provides a sight into local structural transformation in heteroatom doped MHOFs and proposes a novel strategy to modulate structural microenvironment of MOFs materials towards electrochemical applications.

Ca2+ doped metal organic frameworks for enhanced photocatalytic ammonia synthesis

Photocatalytic NH3 synthesis from N2 is a clean and sustainable approach, however, the efficiency of this process is low due to the difficult activation of NN triple bonds. Herein, we propose a metal-doping strategy to facilitate the interfacial charge transfer for promoting the photocatalytic NH3 yield. Ca2+ with low electronegativity was doped in UiO-66-NH2, a kind of Zr-based MOFs, to increase the electron donor capacity of Zr active sites. The X-ray photoelectron spectroscopy (XPS) spectra and density functional theory (DFT) calculations show that the Ca2+ doping enhances the electron density of Zr active sites. Moreover, the diamino ligand is incorporated to tune the bandgap structure of MOFs to expand its light absorption range. By adjusting the ratio of metals and organic ligands, the optimal photocatalyst UN(Zr-0.30Ca)-4 reaches a high NH3 evolution rate of 759.3 μmol g−1 h−1 under full spectrum. This study may provide some inspiration for the design of advanced photocatalysts for diverse chemical reduction reactions.

Synthesis and Application of Doped Metal-Organic Framework (MOF) Nanomaterials

In recent years, MOF has been widely studied as new material. Due to its structure’s diversity, flexibility, and tunability, it is favoured by many scholars and has been used in many fields. However, due to the diversity of MOF types and the wide range of applications, there is a lack of systematic description of the application of MOF materials at present. This paper concluded several aspects of the application of MOF to close this loophole. In this paper, the preparation method including the gas-phase method, hydrothermal method, and liquid-phase epitaxy method of the MOF is introduced, then followed by the method of bringing metal nanoparticles into the prepared frame to make the doped MOF including the impregnation method and double solvent method, and then by adsorption, catalysis, and gas sensor, three aspects are briefly introduced MOF in these fields of application are introduced in these areas in different refining branch such as carbon monoxide adsorption, catalytic hydrogenation, and alkanes as nitric oxide gas sensor. Meanwhile, the challenges for this kind of material are long-term stability, heat resistance, and high cost. This paper is expected to summarize the application of MOF and hope it can bring more economic benefits and scientific value.

Rational design of copper(I)-doped metal-organic frameworks as dual-functional nanocarriers for combined chemo-chemodynamic therapy.

Combination therapies are an increasingly important part of the antitumor medicine armamentarium. However, developing desirable nanomaterials for combination therapies is still a great challenge. Herein, a biocompatible Cu(I)-doped metal-organic framework (MOF) (denoted as CuZn-ZIF) is designed as a novel dual-functional nanocarrier. Doxorubicin molecules are covalently bound to the surface of the CuZn-ZIF and released by the cleavage of chemical bonds in an acidic environment, demonstrating the capacity of controlled drug release. More importantly, CuZn-ZIF nanocarriers can simultaneously play the role of nanocatalysts, capable of catalyzing H2O2 into a highly reactive intracellular toxic hydroxyl radical (˙OH). An in vivo study reveals that nanoparticles exhibit high antitumor efficacy through the combined performance of DOX and Cu(I), proving the great potential of this copper(I)-based MOF for combined chemo-chemotherapy to improve therapeutic efficacy.

Synthesis and characterization of single-phase Tb3+/Eu3+ doped metal-organic framework phosphors for warm light WLED applications.

A novel single-phase luminescent material, Ln@bio-MOF-1 (Ln: Tb3+ and Eu3+), was synthesized by a facile hydrothermal method. The structural and luminescence characteristics of the MOF materials were studied in detail. The chromaticity of the as-prepared samples might be easily modulated using molar amounts of Tb3+ and Eu3+. Sample Tb/Eu@bio-MOF-1 (1) demonstrates a white emission (CIE coordinates: 0.328, 0.338), which is very close to the standard white light (0.333, 0.333). Tb/Eu@bio-MOF-1 (1) has a quantum yield of 52.9%, which is higher than those in most reported works. The corresponding LED devices were prepared to further explore the possible applications of Ln@bio-MOF-1 in WLEDs. The achieved LED device has a high color rendering index (CRI) of 86.2 and a low correlated color temperature (CCT) of 4725 K, which indicates that Tb/Eu@bio-MOF-1 (1) might be a feasible luminescent material for WLED applications.

High-performance atomic Co/N co–doped porous carbon catalysts derived from Co–doped metal–organic frameworks for oxygen reduction

Improving the activity and durability of carbon-based catalysts is a key challenge for their application in fuel cells. Herein, we report a highly active and durable Co/N co-doped carbon (CoNC) catalyst prepared via pyrolysis of Co–doped zeolitic–imidazolate framework–8 (ZIF–8), which was synthesized by controlling the feeding sequence to enable Co to replace Zn in the metal–organic framework (MOF). The catalyst exhibited excellent oxygen reduction reaction (ORR) performance, while the half-wave potential decreased by only 8 mV after 5,000 accelerated stress test (AST) cycles in an acidic solution. Furthermore, the catalyst exhibited satisfactory cathodic catalytic performance when utilized in a hydrogen/oxygen single proton exchange membrane (PEM) fuel cell and a Zn-air battery, yielding maximum power densities of 530 and 164 mW cm−2, respectively. X-ray absorption spectroscopy (XAS) and high-angle annular dark field-scanning transmission electron microscopy (HAAD–STEM) analyses revealed that Co was present in the catalyst as single atoms coordinated with N to form Co–N moieties, which results in the high catalytic performance. These results show that the reported catalyst is a promising material for inclusion into future fuel cell designs.

Intelligent Clinical Lab for the Diagnosis of Post-Neurosurgical Meningitis Based on Machine-Learning-Aided Cerebrospinal Fluid Analysis.

Post-neurosurgical meningitis (PNM) often leads to serious consequences; unfortunately, the commonly used clinical diagnostic methods of PNM are time-consuming or have low specificity. To realize the accurate and convenient diagnosis of PNM, herein, we propose a comprehensive strategy for cerebrospinal fluid (CSF) analysis based on a machine-learning-aided cross-reactive sensing array. The sensing array involves three Eu3+-doped metal-organic frameworks (MOFs), which can generate specific fluorescence responding patterns after reacting with potential targets in CSF. Then, the responding pattern is used as learning data to train the machine learning algorithms. The discrimination confidence for artificial CSF containing different components of molecules, proteins, and cells is from 81.3 to 100%. Furthermore, the machine-learning-aided sensing array was applied in the analysis of CSF samples from post-neurosurgical patients. Only 25 μL of CSF samples was needed, and the samples could be robustly classified into "normal," "mild," or "severe" groups within 40 min. It is believed that the combination of machine learning algorithms with robust data processing capability and a lanthanide luminescent sensor array will provide a reliable alternative for more comprehensive, convenient, and rapid diagnosis of PNM.

CoNi alloy anchored onto N-doped porous carbon for the removal of sulfamethoxazole: Catalyst, mechanism, toxicity analysis, and application

Developing highly efficient, stable, recyclable, and application value heterogeneous catalysts in advanced oxidation processes has essential application value in the degradation of refractory pollutants. In this paper, the CoNi alloy anchored onto N-doped porous carbon (CoNi-600@NC) catalyst was prepared using bimetallic doped metal-organic frameworks as precursors. The magnetic CoNi-600@NC can activate peroxymonosulfate (PMS) to degrade sulfamethoxazole (SMX). Therefore, SMX can be removed 100% within 25 min. CoNi-600@NC/PMS has a broad pH (3–9) application range, good applicability, and repeatability. Radical quenching, quantitative and electrochemical experiments proved that the degradation of SMX was dominated by free radical (Superoxide anions) and non-free radical pathways (surface-bound radicals). Mechanistic analysis showed that the interaction between Co-Nx/pyridine N-sites and graphitized carbon with PMS induced the formation of surface-bound active species. Moreover, CoNi nanoparticles promoted the redox cycle of metals. The synergistic catalytic mechanisms between the CoNi alloy and the abundant functional groups gave CoNi-600@NC excellent catalytic properties and applicability. Using density functional theory predicted the reaction sites of SMX and proposed four degradation pathways. The toxicity of intermediates was comprehensively evaluated. In addition, a CoNi-600@NC continuous flow reactor was constructed with a daily treatment capacity of 45 L and 100% SMX removal. This study expands the application of persulfate advanced oxidation technology by synthesizing recyclable magnetic catalysts and provides new synergistic degradation mechanisms for removing refractory organics.

Metal‐ organic frameworks and their derivatives as anode material in lithium‐ion batteries: Recent advances towards novel configurations

Lithium-ion batteries (LIBs) have drawn extensive research interests due to their noticeably enhanced gravimetric energy density relative to other chemical batteries. The potential utility of metal-organic frameworks (MOFs) and their derivatives has recently been recognized as highly effective anode components for LIBs because they can be tuned to select specific metal sites and/or to adjust pore sizes. In this work, their electrochemical performance as anodic materials is carefully evaluated with respect to lithium-ions storage capacity, energy/power, stability, and flexibility. Furthermore, through the coordination of the organic linker and metal center, MOFs can benefit from enhanced catalytic activities in the design of advanced LIBs. For future research for next-generation LIBs, scientific focus should be placed on the development of diverse features of MOF-based composites such as core-shell MOFs, mono/bi-metal doped MOFs, dual organic linker-based MOFs, MOFs@MOFs core shell structure, and dual organic ligands-based MOF. As such, MOF-based LIB electrode materials are expected to expand their utility with the improvement in topology and functionality in association with the dimensionality, pore size, and surface area.

Electrochemical sensing of malathion using doped MOFs

Coordination polymerization produces a variety of metal-organic frameworks (MOFs), each with its own set of physical & chemical properties. Making MOFs suitably conductive in nature, is one of the hurdles faced to be utilized its potential practical applications. To explore the electrical conductivity’s features of MOFs, NH2-Al-MOF, ZnQ@ZIF-8 and Al-MIL-53 MOF have been treated with NaOH, H2SO4, and HCl. Acid/Alkaline doped MOFs have been utilized to prepare conducting thin films on indium tin oxide (ITO) slides using drop-casted method. Electrical feature analysis has indicated reduction in overall resistance of NH2-Al-MOF < ZnQ@ZIF-8 < Al-MIL-53. The prepared MOFs thin films have been used for malathion detection. We have found limit of detection (LOD) i.e., 1.668 mg/L 2.386 mg/L and 2.397 mg/L for malathion using doped MOFs, respectively.

Fabrication of Ce-doped DUT-52 as a sorbent for dispersive solid phase extraction of estrogens in human urine samples.

A cerium (Ce)-doped metal-organic framework composite (Ce/DUT-52) was prepared by using a solvothermal method and was explored as a sorbent for dispersive solid phase extraction (DSPE) of three estrogens (α-estradiol, estrone, and hexestrol) in human urine samples. After doping with Ce(III), Ce/DUT-52 exhibited more attractive features involving a higher specific surface area (774.7 m2 g-1) and zeta potential (31.4 mV), which made it an efficient adsorbent for the separation and enrichment of estrogens. The factors influencing DSPE efficiency such as the adsorbent amount, extraction time, pH, NaCl concentration, elution solvent and elution volume were investigated in detail. Under the evaluated conditions, Ce/DUT-52 showed good reusability (n = 6, RSDs ≤ 4.8%). Notably, the cofunction of electrostatic interaction, hydrophobic interaction, hydrogen bonding and π-π interaction might play major roles between estrogens and Ce/DUT-52. Finally, coupled with high-performance liquid chromatography (HPLC), a fast and sensitive method was established, which provided low limits of detection (1.5-2.0 ng mL-1), wide linear ranges (3-500 ng mL-1) and satisfactory recoveries (79.8-96.1%). The results demonstrated that Ce/DUT-52 had excellent adsorption ability to the targets and the developed method provided an alternative strategy for the determination of trace estrogens or other compounds with similar chemical structures in urine samples.

Self-sustained bioelectrical reduction system assisted iron–manganese doped metal-organic framework membrane for the treatment of electroplating wastewater

Heavy metals seriously endanger human health. However, simultaneous and efficient removal of heavy metals from wastewater has always been a technical challenge. For this purpose, we developed a self-sustained bioelectrical reduction system (SBRS) for the efficient purification of heavy metal wastewater. A novel iron-manganese doped metal-organic framework membrane (FM-MOFM) based on conductive substrate is used as the catalytic cathode electrode. The performances of the SBRS assisted FM-MOFM for heavy metals reduction and self-energy generation for the treatment of simulated electroplating wastewater were investigated. The FM-MOFMs were characterized before and after operation by SEM, XRD, XPS and other methods. Copper, zinc, chromium, nickel heavy metal ions are almost completely removed by the SBRS (removal efficiency: Copper ion 99.9%, Zinc ion 99.9%, Chromium ion 99.7% and Nickel ion 99.8%). Moreover, the organic substrates in the wastewater were removed simultaneously and efficiently (removal efficiency: COD 95.3%, NH4+-N 99.9%, TP 95.9%), with the maximum power density of 1.6 W m−3. The possible electroreduction and electroflocculation mechanism of heavy metal ions can be understood by the characterization of the membrane electrode surface and precipitate. The study confirms that the SBRS is a potential and efficient candidate for the simultaneous removal of heavy metals from electroplating wastewater.

PH-responsive aminotriazole doped metal organic frameworks nanoplatform enables self‐boosting reactive oxygen species generation through regulating the activity of catalase for targeted chemo/chemodynamic combination therapy

The rational integration of chemotherapy and hydroxyl radical (·OH)-mediated chemodynamic therapy (CDT) via functional metal–organic frameworks (MOF) carriers has great potential in cancer therapy. In this work, aminotriazole (3-AT) doped polyhedral metal organic frameworks (denoted as MAF) were prepared by template ligand replacement, where CDT was initiated by Cu2+/Cu+ modulated Fenton reaction and enhanced by effectively regulating the catalase activity with 3-AT. However, a rod-like Cu-MOF with 3-AT served as a ligand was obtained by the hydrothermal method without using template. In contrast to Cu-MOF, pH-responsive MAF was chosen as the carrier for targeted drug delivery due to its higher drug load of 17.6% and relatively uniform size, where doxorubicin (DOX) as a model drug was loaded in its cavity and hyaluronic acid (HA) was coated on its surface via electrostatic interactions (denoted as HA-MAF@DOX). In vitro experiments demonstrated that HA-MAF@DOX had high transport efficiency of DOX, effective regulation of catalase (CAT) activity and enhanced cytotoxicity to HepG2 cells. This work is the first use of enzyme inhibitors as ligands to construct functional MOFs via template ligand replacement for effective regulating enzyme activity, mediating intracellular redox homeostasis and enhancing CDT efficacy, which provides a feasible strategy for the construction the functional MOFs in cancer therapy.