Functional Metal-organic Frameworks Research Articles

Rational design of stable functional metal-organic frameworks.

Functional porous metal-organic frameworks (MOFs) have been explored for a number of potential applications in catalysis, chemical sensing, water capture, gas storage, and separation. MOFs are among the most promising candidates to address challenges facing our society related to energy and environment, but the successful implementation of functional porous MOF materials are contingent on their stability; therefore, the rational design of stable MOFs plays an important role towards the development of functional porous MOFs. In this Focus article, we summarize progress in the rational design and synthesis of stable MOFs with controllable pores and functionalities. The implementation of reticular chemistry allows for the rational top-down design of stable porous MOFs with targeted topological networks and pore structures from the pre-selected building blocks. We highlight the reticular synthesis and applications of stable MOFs: (1) MOFs based on high valent metal ions (e.g., Al3+, Cr3+, Fe3+, Ti4+ and Zr4+) and carboxylate ligands; (2) MOFs based on low valent metal ions (e.g., Ni2+, Cu2+, and Zn2+) and azolate linkers. We envision that the synthetic strategies, including modulated synthesis and post-synthetic modification, can potentially be extended to other more complex systems like metal-phosphonate framework materials.

Functional metal–organic frameworks as adsorbents used for water decontamination: design strategies and applications

We summarized the strategy for constructing functional metal–organic frameworks (MOFs) and their applications in the adsorption of water contaminants.

Palladium Schiff base complex-modified Cu(BDC-NH2) metal-organic frameworks for C-N coupling.

In this study, the synthesis of a novel functionalized metal-organic-framework (MOF) [Cu(BDC-NH2)@Schiff-base-Pd(ii)] catalyst via post-synthetic modification of Cu(BDC-NH2) is reported. The targeted complex was prepared by chemically attaching N,N'-bis(5-formylpyrrol-2-ylmethyl) homopiperazine via a Schiff base reaction followed by complexation with Pd ions. Afterwards, the synthesized solid was applied as a very effective multifunctional catalyst in C-N coupling reactions. The synthesized compounds were identified by suitable techniques including N2 isotherms, EDX spectroscopy, FT-IR spectroscopy, XRD, SEM, ICP-OES and TG-DTA. This nanocatalyst was used in C-N cross-coupling reactions, and it showed its usage in a diverse range of different functional groups with good efficiency. The reasons for introducing this catalyst system are its advantages such as considerably high selectivity, almost complete conversion of products, high yields, and convenient separation of catalysts and products. The results indicate that the highest efficiency of the product in the reaction was obtained in the shortest possible time with the use of [Cu(BDC-NH2)@Schiff-base-Pd(ii)] catalysts. Overall, the high catalytic activity of the [Cu(BDC-NH2)@Schiff-base-Pd(ii)] catalyst may be due to the obtained high surface area and the synergistic features created between Lewis acidic Cu nodes and Pd ions.

A thiol-containing zirconium MOF functionalized with silver nanoparticles for synergistic CO2 cycloaddition reactions.

Thiol-containing biomolecules, such as cysteine and glutathione, play essential roles in regulating the polarity and reactivity of the systems. Among functional MOFs, thiol MOFs, a subclass with a thiol group-containing ligand, are relatively less explored due to their synthetic challenges and stability and storage issues. Despite these drawbacks, they have many advantages due to the electronically soft thiol groups with strong reactivity and affinity toward soft metal ions. Herein, we have taken advantage of the affinity between thiol groups and a soft metal (Ag) by functionalizing a thiol MOF with Ag ions and finally synthesizing a silver nanoparticle-functionalized heterogeneous catalyst (Ag@Zr-DMBD). The Zr,Ag centre of the thiol MOF catalyst acts as an active centre and synergistically binds with the electron-rich oxygen atom of a terminal epoxide for efficient CO2 fixation to the corresponding cyclic carbonates under atmospheric CO2 pressure in 8 h. Finally, a rationalized reaction mechanism is proposed based on literature reports and current results. This work presents a viable strategy for using thiol MOFs as heterogeneous catalysts for CO2 fixation under mild conditions.

Multi-functionalized MOFs with large-pore apertures as luminescent probes for efficient sensing of quinones

Two functionalized metal–organic frameworks based on azobenzene and azine groups were synthesized and characterized. The ability of these materials as luminescent probes towards quinones was investigated and compared.

Ionic liquid functionalized metal-organic framework nanowires for sensitive and real-time electrochemical monitoring of nitric oxide released from living cells.

Sensitive, selective, and real-time detection of nitric oxide (NO) is still challenging due to its rapid diffusion, short half-life, and low concentration in living systems. Herein, we synthesized well-defined ultralong metal-organic framework nanowires (MOFNWs) that were further uniformly covered with gold nanoparticle (AuNPs) and ionic liquids (ILs) and applied these NWs to detect and monitor NO released from living cells. In this system, ILs and AuNPs act as excellent catalysts for electrochemical oxidation of NO. By taking advantage of the synergetic effect between ILs, AuNPs and MOFNWs, the composite (IL@Au@MOFNWs) sensor probe displays excellent electrocatalytic activity toward NO oxidation with a detection limit as low as 2.28 nM for NO detection. The high levels of selectivity and sensitivity to NO in complex biological environments can be attributed to the exposed Ni2+ active sites, high ion-electron transport rates of NWs, and the high conductivity of ILs and AuNPs. Furthermore, the IL@Au@MOFNWs offer a biocompatible sensing interface enabling rapid real-time monitoring of NO released from living cells by drug stimulation. Collectively, these results demonstrate that functionalized ultralong MOFNWs exhibit a remarkable ability to quantify NO levels in cells and could therefore provide new potential of this sensor in electrochemical detection of living bodies.

Porous functional metal–organic frameworks (MOFs) constructed from different N-heterocyclic carboxylic ligands for gas adsorption/separation

This review mainly summarizes the recent progress of MOFs composed of N-heterocyclic carboxylate ligands in gas sorption/separation. This work may help to understand the relationship between the structures of MOFs and gas sorption/separation.

Functionalized metal–organic frameworks based on multi-catalyst ordered assembly for electrochemical stripping chemiluminescent immunoassay

The synergic catalysis can greatly improve the performance of sensor developed.

Rational design of a functionalized metal-organic framework for ratiometric fluorimetric sensing of Hg2+ in environmental water.

A target-responsive ratiometric fluorimetric sensing strategy for Hg2+ has been rationally designed. The sensing probe was established based on a functionalized metal-organic framework, which was prepared with 3,5-dicarboxyphenylboronic acid (DCPB) as the functional ligand and Eu3+ as the metal junction. The porous nano-spheres of Eu-MOF with an arylboronic acid as the functional recognition group for Hg2+ exhibited tunable optical properties with dual emission fluorescence signals at 338 nm and 615 nm. In the presence of Hg2+, arylmercury was formed by a specific transmetalation reaction between Hg2+ and arylboronic acid groups, which blocks the energy transfer between the ligand and Eu3+. Thereby, the fluorescence signal of Eu-MOF/BA at 615 nm decreased, while the fluorescence signal at 338 nm remained almost constant. The ratiometric fluorimetric sensing for Hg2+ was achieved by calculating the peak intensity ratio of F615/F338 based on the reference signal at 338 nm and the response signal at 615 nm. The detection limit of Hg2+ was as low as 0.0890 nM, and the recovery rate of the actual environmental water sample ranged from 90.92% to 118.50%. Therefore, the excellent performance of the ratiometric fluorimetric sensing method for Hg2+ makes it attractive for the detection of heavy metal ions in environmental monitoring.

Recent advances and future perspectives in MOF-derived single-atom catalysts and their application: a review

This article discusses the relationship between single-atom sites and the catalytic mechanism of functional MOFs which is related to the coordination environment of metal ions, and also summarizes the research progress of MOF-derived SACs in recent years.

An ordered conductive Ni-CAT nanorods array as all-round polysulfide regulator for lithium-sulfur batteries

The effective suppression of polysulfide shuttle is indispensable for the commercialization of lithium-sulfur batteries (LSBs). In this work, an ordered conductive metal-organic framework (MOF) Ni-CAT nanorods array rooted on carbon nanotube film (Ni-CAT/CNTF) is proposed for this subject. The well-aligned MOF nanorods array possesses a unique vertical structure, presenting an incompact upper part and dense root, which guarantee the highly efficient adsorption and selective sieving towards polysulfides, respectively, as well as a fast Li+ transfer. What's more, the good electrical property and fully exposed Ni-based catalytic sites are qualified to boost the electrochemical kinetics. Consequently, LSBs with this fully functional MOF nanorods array exhibit an astonishing capacity of 1087 mAh g−1 and an extraordinary cyclability with a finite capacity-fading of only 0.026% per cycle for 1000 cycles at 1 C, along with an exceptional rate performance of 754 mAh g−1 at 5 C. Moreover, outstanding cycle and rate performance can be maintained under elevated sulfur loadings with a reduced electrolyte content. This work offers new insights into the rational design of polyfunctional nanostructures in LSBs.

Systematic investigation of PFOS adsorption from water by Metal Organic Frameworks, Activated Carbon, Metal Organic Framework@Activated Carbon, and functionalized Metal Organic Frameworks

The presence of Per- and Polyfluoroalkyl Substances (PFAS) in water causes health effects on humans and animals over time. Among all techniques, the adsorption methodology has shown effective performance in removing PFAS from water. Different adsorbents, including classical powder activated carbon (AC) and Metal Organic Frameworks (MOFs) as a new generation of adsorbents have been used for the removal of short-chain (C < 6) and long-chain (C > 7) PFAS. However, due to the complexity of the adsorption process, the diversity of adsorbents and PFAS compounds, and the lack of standard experimental protocol, the effectiveness and undergoing sorption mechanisms for each of these adsorbents have not been investigated and compared systematically yet. In this work, we synthesized and characterized the adsorbents and then performed a systematic isotherm adsorption protocol to study the adsorption mechanisms and performance of adsorbents, including nanosized activated carbon AC, MIL-101 (Cr), MIL-101 (Cr)–NH2 and novel hybrid adsorbent MIL-101 (Cr)@AC for the removal of perfluorooctane sulfonic acid (PFOS) from water. Based on the comparative analysis to investigate the effective parameters governing the PFOS adsorption with respect to each adsorbent, AC with around 93 % PFOS removal showed supreme performance over other MOFs; however, MOF-based adsorbents showed faster adsorption compared to AC. The MIL-101(Cr)@AC (with 80 % removal performance and 2 h adsorption time) possessed the advantages of both AC and MIL-101 (Cr). The hydrophobic-hydrophobic and electrostatic interactions were the main dominant adsorption interactions for AC and MOFs, respectively, while both interactions were influential in the MIL-101 (Cr)@AC adsorption. All adsorbents were regenerated, and AC showed the best regeneration efficiency (>70 %) after 4 cycles.

Double Crosslinked Polymer Electrolyte by C–S–C Group and Metal–Organic Framework for Solid‐State Lithium Batteries

Poly(ethylene oxide) (PEO) is among the most promising candidates for solid‐state electrolytes in lithium metal batteries. However, the low ionic conductivity caused by strong coordination between Li ions and the EO chains limits the practical application of PEO‐based electrolytes. Herein, a double crosslinked PEO‐based electrolyte with alternate C–S–C groups and functionalized metal–organic frameworks (MOFs) is proposed. The incorporation of C–S–C groups not only accelerates Li ions transport by weakening the coordination between Li ions and polymer backbone, but also facilitates segmental relaxation of the polymer backbone. The PEO‐based electrolyte with C–S–C groups shows a remarkable 13‐fold increase in ionic conductivity. Furthermore, when functionalized MOFs are used as crosslinked centers, the double‐crosslinked PEO‐based electrolyte with a robust network structure possesses enhanced mechanical/electrochemical/thermal stability and limited anion transmission. As a result, the symmetrical Li||Li cell enables over 2400 h cycling at room temperature. The LiFePO4||Li cells show long cycle life over a wide temperature range from 25 to 100 °C, and a high areal capacity of 1.43 mAh cm−2 is achieved with a cathode loading of 10.0 mg cm−2. This study demonstrates a promising strategy to develop advanced electrolytes for potential solid‐state lithium‐metal batteries.

A Cluster Based Cooperative Kinetic Model for CO2 Adsorption on Amine Functionalized Metal–Organic Frameworks

A new model for the adsorption kinetics of CO2 on amine functionalized metal–organic frameworks Mg2 (dobpdc) and Mn2 (dobpdc) is proposed. The equilibrium adsorption is evaluated using the cooperative lattice theory of Kundu et al. The lattice theory provides a microscopic interpretation of adsorption behavior on the basis of the state of adsorbed CO2: singly adsorbed, chain ends, and chain interiors. On this basis, the proposed kinetic model accounts for the kinetics of singly adsorbed CO2, as well as the kinetics of adsorption into chains. These two kinetic paths have separate yet coupled rate laws. This allows for the accurate description of complex kinetic phenomena observed in low partial pressure CO2 breakthrough curves on mmen-Mg2 (dobpdc). In addition to good numerical agreement with measured data, the approach developed in this work provides a needed microscopic interpretation of measured kinetic data in these systems. This microscopic picture may allow for more targeted material design and a pathway to include additional factors such as the effect of humidity on CO2 adsorption and kinetics.

Selective and moisture-sensitive degradation of bromocresol green for isostructural MOFs assembled with D-camphorate and bipyridine

A novel 2D manganese MOFs exhibits selective photodegradation of bromocresol green which can be promoted by moisture owing to the sensitivity for the Mn-O bonds. • Synthesis and characterization of 2D corrugated structure. • Selective photodegradation of BCG. • Promotion of degradation of BCG by Moisture owing to the sensitive of coordination bonds. Three new isostructural metal-organic frameworks, [M 2 (D-cam) 2 (4,4’-bpy)(H 2 O) 4 ] (D-cam 2- = D-camphorate, 4,4’-bpy = 4,4’-bipyridine, M = Mn ( 1-Mn ), Co ( 1-Co ), and Ni ( 1-Ni )), have been synthesized and fully characterized. The complexes, crystallizing in chiral space group, P 2 1 , are AA-stacking corrugated layers with hcb topological networks composed of homochiral coordination chains, M(D-cam), and auxiliary ligands. Notably, the solubility in water for three MOFs decrease in accordance with Irving-Williams series, indicating the good moisture-sensitivity for 1-Mn . Furthermore, the photolysis experiments of dyes reveal that only 1-Mn can catalyze the degradation of bromocresol green (BCG) rapidly and selectively, which can pave a way to explore more prolific functional MOFs in catalysis. CCDC: 2158741

Fabrication of nanocomposite membrane based on post-synthetic modification of two-dimensional metal-organic framework nanosheet

• Post-synthetic modification of two-dimensional metal-organic framework. • CuBDC-NH 2 nanosheet reacts with isocyanate-terminated polyurethane oligomer(PU). • The CuBDC-NH 2 /PU is conducted to prepare functional nanocomposite membrane. • The CuBDC-NH 2 /PU membrane shows over 93.0% removal rate for dye removal. Two-dimensional metal-organic framework (2D MOF) nanosheet is becoming as an attractive type of 2D materials. And Post-synthetic modification (PSM) provides a powerful method to modify the structure of MOF without altering its crystal topology, which can generate functional MOFs not accessible from direct synthesis and improve the compatibility between MOFs and other components in MOF-based composite materials, especially in MOF/polymer composite. In this work, a facile method based on PSM of 2D MOF with polymers is conducted to prepare functional nanocomposite membrane. First, the amino-functioned 2D MOF nanosheet, CuBDC-NH 2 (BDC-NH 2 is 2-amino-1,4-benzenedicarboxylate), has been prepared as PSM precursor. Then CuBDC-NH 2 nanosheet reacts with isocyanate-terminated polyurethane (PU) oligomer through PSM to obtain CuBDC-NH 2 /PU nanocomposite membrane, which show over 93.0% removal rate for dye removal, such as methylene blue, Rhodamine B and Eosin Y.

A Novel Dual-Emission Fluorescence Probe Based on CDs and Eu3+ Functionalized UiO-66-(COOH)2 Hybrid for Visual Monitoring of Cu2.

In this work, CDs@Eu-UiO-66(COOH)2 (denoted as CDs-F2), a fluorescent material made up of carbon dots (CDs) and a Eu3+ functionalized metal-organic framework, has been designed and prepared via a post-synthetic modification method. The synthesized CDs-F2 presents dual emissions at 410 nm and 615 nm, which can effectively avoid environmental interference. CDs-F2 exhibits outstanding selectivity, great sensitivity, and good anti-interference for ratiometric sensing Cu2+ in water. The linear range is 0-200 µM and the limit of detection is 0.409 µM. Interestingly, the CDs-F2's silicon plate achieves rapid and selective detection of Cu2+. The change in fluorescence color can be observed by the naked eye. These results reveal that the CDs-F2 hybrid can be employed as a simple, rapid, and sensitive fluorescent probe to detect Cu2+. Moreover, the possible sensing mechanism of this dual-emission fluorescent probe is discussed in detail.

A durable MOF-303-coated stainless steel mesh with robust anti-oil-fouling performance for multifunctional oil/water separation

Durable anti-fouling membranes for the effective and simultaneous removal of insoluble oil droplets and organic dyes from wastewater need to be developed urgently. Metal–organic frameworks (MOFs) are emergent porous organic–inorganic hybrid materials, that have been attracting increasing attention because of wide applications, such as liquid separation, dye adsorption, and catalysis. However, the preparation of a well-intergrown MOF membrane remains challenging, because of poor water stability and low affinity between MOF grains and substrates. Herein, we report the first preparation of a continuous, water-stable MOF-coated mesh with an ordered porous structure by using a simple hydrothermal method to realize array growth of MOF-303 crystals on a layered double-hydroxide modified mesh surface. As the MOF-303 has a high water uptake capability, the prepared MOF-303 @SSM with sufficient surface hydration exhibited superhydrophilicity-underwater superoleophobicity and excellent antifouling performance. This membrane was used for gravity-driven separation of oil/water mixtures at high flux (> 12308 L m−2 h−1) and efficiency (> 99.35%). This membrane simultaneously and efficiently removed an oil-in-water (O/W) emulsion and water-soluble dyes, and exhibited outstanding reusability. More importantly, MOF-303 @SSM is promising for practical applications because of outstanding physical and chemical stability, as well as high thermal stability, under harsh environmental conditions. Therefore, this study provides a promising strategy to develop a functional MOF membrane for purifying hazardous wastewater.

MOFs and bone: Application of MOFs in bone tissue engineering and bone diseases

Metal-organic frameworks (MOFs), a class of hybrid materials, consist of organic linkers and bridging metal ions or clusters. Their tunable pore sizes, large surface area, good biocompatibility, structural variability in combination with materials and chemicals, and osteogenic effects provide potential approaches for bone tissue engineering and bone diseases. And there are more and more research on MOFs in the field of osteogenesis in recent years. This review presents an overall summary of the application in the bone tissue engineering and bone diseases of MOFs and their composites, starting with the synthesis of MOFs, which discusses the advantages and disadvantages of different syntheses. Then, the biological functions of MOFs are discussed, which are the basics of MOFs applied in the organism. Importantly, mechanisms and abundant applications of MOFs are detailed in the bone tissue engineering and bone diseases. Finally, some prospects of MOFs are discussed, for instance, exploring whether MOFs can be used to treat other bone diseases.

Modulated Hydrothermal Chemistry of Metal–Organic Frameworks

ConspectusMetal–organic frameworks (MOFs) are infinite networks composed of inorganic metals and organic linkers, and have demonstrated superior advantages over traditional porous materials in gas storage, separation, catalysis, etc., because of possessing ultrahigh surface areas and tunability in pore sizes, topologies, shapes, and functionalities. Although tremendous progress has been made in the fundamental research and applications of MOFs, developing a green and large-scale approach to synthesizing MOFs with repeatably high quality remains a key step for their massive production and industrial applications. Traditional solvothermal and hydrothermal approaches usually synthesize MOFs on a small scale with challenges in quality control. In addition, these synthetic processes typically require high temperatures, high pressures, and sometimes large amounts of environmentally unfriendly organic solvents. In this Account, we elaborate on the recent progress of the modulated hydrothermal (MHT) chemistry developed by us, which helps synthesize zirconium/hafnium-based MOFs in green (aqueous solutions), mild (≤120 °C, 1 atm), and scalable fashion. The MHT chemistry has already served as a solid foundation for the design and scale-up synthesis of multifunctional MOF materials by tuning the types and concentrations of ligands and modulators and their ratios. It not only applies to the classical UiO-66-type and MOF-808-type MOFs, but also suits the design of new MOFs, such as NUS-6, NUS-8, and NUS-36. In addition, the MHT-enabled MOFs have demonstrated promising applications in gas separation and storage, Lewis/Brønsted acid-catalyzed oxidation reactions/biomass conversion, and piezoelectric/ferroelectric devices. This Account further prospects the evolution of MHT chemistry in developing new functional MOFs composed of different metals, such as titanium, zirconium, hafnium, cerium(IV), etc., on a large scale and sustainable paradigm.