Functional Metal-organic Frameworks Research Articles

Modular Functionalization of Metal‐Organic Frameworks for Nitrogen Recovery from Fresh Urine**

AbstractNitrogen recovery from wastewater represents a sustainable route to recycle reactive nitrogen (Nr). It can reduce the demand of producing Nr from the energy‐extensive Haber‐Bosch process and lower the risk of causing eutrophication simultaneously. In this aspect, source‐separated fresh urine is an ideal source for nitrogen recovery given its ubiquity and high nitrogen contents. However, current techniques for nitrogen recovery from fresh urine require high energy input and are of low efficiencies because the recovery target, urea, is a challenge to separate. In this work, we developed a novel fresh urine nitrogen recovery treatment process based on modular functionalized metal–organic frameworks (MOFs). Specifically, we employed three distinct modification methods to MOF‐808 and developed robust functional materials for urea hydrolysis, ammonium adsorption, and ammonia monitoring. By integrating these functional materials into our newly developed nitrogen recovery treatment process, we achieved an average of 75 % total nitrogen reduction and 45 % nitrogen recovery with a 30‐minute treatment of synthetic fresh urine. The nitrogen recovery process developed in this work can serve as a sustainable and efficient nutrient management that is suitable for decentralized wastewater treatment. This work also provides a new perspective of implementing versatile advanced materials for water and wastewater treatment.

Computational quantum chemistry of metal–organic frameworks

Metal–organic frameworks (MOFs) have premium exceptional properties for a variety of functions, such as gas separation and storage and catalysis. The large variety of possible inorganometallic nodes and organic linkers provide an almost unlimited number of combinations for assembling MOFs, which makes the experimental characterization and examination of all potentially useful combinations practically impossible. Furthermore, experimental studies of MOFs typically fall short in uncovering crucial details regarding their mechanisms of action or the molecular details responsible for their functional properties, such as the nature of adsorbate binding or the structures of transition states. Computational modeling has, therefore, become an efficient and important tool for strategizing the functionalization of MOFs and explicating the mechanisms of their functions. Here, we review the computational methodologies used for computational studies of MOFs, especially Kohn–Sham density functional theory and combined quantum mechanical and molecular mechanical methods for calculating their structural, electronic, and magnetic properties, as well as for understanding the mechanisms of MOFs' applications to magetic devices, thermal conduction, gas adsorption, separation, storage, and sensing, thermal catalysis, photocatalysis, and electrocatalysis.

Porous 3D and 2D frameworks differentiation induced by metal doping: Structure flexibility, capture behaviors, post-synthetic metal exchange and amorphous electrocatalyst transformation

The obtaining of high porosity and understanding the dynamic pore responses to various inclusion guests represents one main focus in the functionalization of metal-organic frameworks (MOFs). A new solvothermally generated MOF of {(Me2NH2)[Ni3(μ3OH)(tzba)3(H2O)3]}·8DMF (Ni3−MOF, H2tzba = 4-(1H-tetrazol-5-yl)benzoic acid) processes negative charged, new triangular [Ni3(μ3OH)(COO)3(tz)3(H2O)3] node based, MIL-88-topology resembled framework, with high void fraction of 73.3%. While the introduction of equivalent Mn2+ will greatly change the coordination assembly, leading to 2D (3,6)-grid layer of [Ni1.4Mn1.6(tzba)3(H2O)6]·12DMF (NiMn-MOF) as the first example of synergistical construction of rare [M2(tz)3(H2O)3] and [M(COO)3] nodes. The 2D layers parallelly stacked in ABAB fashion through interlayer hydrogen bonding, and generated a neutral framework with high void fraction of 72.9% and 1D mesoporous hexagonal channels with diameter of 24.0 Å. The Ni3−MOF is highly flexible and tends to close its pores after full guest removing, yet its gas accessible porosity is sensitive to residual guest in the pores and the porosity are fully reserved in organic solution phase to capture Methylene Blue and iodine. The inherent strong structure dynamic of Ni3−MOF facilitates post-synthetic metal exchange of the Ni2+ by Mn2+, Co2+, Cu2+ and Cd2+, as well as the in-situ formation of amorphous Ni(OH)2 electrocatalyst for dual water splitting with full recovery of costly organic ligands. For the NiMn-MOF, large gas accessible porosity with Langmuir surface area of 1052 m2 g−1, as well as guest dependent shrink-swell behavior was obtained. The NiMn-MOF is found to be an effective porous adsorbent to capture the iodine in either solution or gaseous phase, with uptake up to 2.4 mol iodine per mol of MOFs and capture of iodine with concentration lower to 5.0 × 10−5 mol/L.

Advances in Metal-Organic Frameworks for the Removal of Chemical Warfare Agents: Insights into Hydrolysis and Oxidation Reaction Mechanisms.

The destruction of chemical warfare agents (CWAs) is a crucial area of research due to the ongoing evolution of toxic chemicals. Metal-organic frameworks (MOFs), a class of porous crystalline solids, have emerged as promising materials for this purpose. Their remarkable porosity and large surface areas enable superior adsorption, reactivity, and catalytic abilities, making them ideal for capturing and decomposing target species. Moreover, the tunable networks of MOFs allow customization of their chemical functionalities, making them practicable in personal protective equipment and adjustable to dynamic environments. This review paper focuses on experimental and computational studies investigating the removal of CWAs by MOFs, specifically emphasizing the removal of nerve agents (GB, GD, and VX) via hydrolysis and sulfur mustard (HD) via selective photooxidation. Among the different MOFs, zirconium-based MOFs exhibit extraordinary structural stability and reusability, rendering them the most promising materials for the hydrolytic and photooxidative degradation of CWAs. Accordingly, this work primarily concentrates on exploring the intrinsic catalytic reaction mechanisms in Zr-MOFs through first-principles approximations, as well as the design of efficient degradation strategies in the aqueous and solid phases through the establishment of Zr-MOF structure-property relationships. Recent progress in the tuning and functionalization of MOFs is also examined, aiming to enhance practical CWA removal under realistic battlefield conditions. By providing a comprehensive overview of experimental findings and computational insights, this review paper contributes to the advancement of MOF-based strategies for the destruction of CWAs and highlights the potential of these materials to address the challenges associated with chemical warfare.

Confinement of Organic Dyes in UiO-66-Type Metal-Organic Frameworks for the Enhanced Synthesis of [1,2,5]Thiadiazole[3,4-g]benzoimidazoles.

Organic dyes as non-noble metal photosensitizers have attracted increasing attention due to their environmental friendliness and sustainability but suffer from fast deactivation and low stability. Here, we reported a fruitful strategy by the confinement and stabilization of visible light-active signal unit organic dyes within the metal-organic frameworks (MOFs) and developed a series of heterogeneous photocatalysts dye@UiO-66s [dye = fluorescein (FL)/rhodamine B (RhB)/eosin Y (EY), UiO-66s = UiO-66, and Bim-UiO-66]. It has been demonstrated that the encapsulated dyes can effectively sensitize MOF hosts and dominate the band structures and photocatalytic activities of dye@UiO-66s regardless of the ligand functionalization of MOFs. Photocatalytic experiments showed that these dye@UiO-66s exhibit enhanced activities relative to free dyes and among them, FL@Bim-UiO-66 displays excellent efficiencies toward the green synthesis of new carbon-bridged annulations, [1,2,5]thiadiazole[3,4-g]benzoimidazoles in the yield of up to 98% at room temperature with outstanding stability and reusability. Furthermore, the intramolecular cyclization intermediate was captured and characterized by the single-crystal X-ray diffraction analysis.

Amino functionalized metal–organic framework as eco-friendly support for enhancing stability and reusability of horseradish peroxidase for phenol removal

Amino functionalized metal–organic framework as eco-friendly support for enhancing stability and reusability of horseradish peroxidase for phenol removal

The synthesis and functionalization of metal organic frameworks and their applications for the selective separation of proteins/peptides.

Recently, proteins separation has drawn great interest for the full investigation of a proteome because the proteins separation is the precondition when conducting clinical research or proteomics research. Metal organic frameworks (MOFs) are fabricated via covalent connection between organic ligands and metal ions/clusters units. MOFs have attracted much attention due to the ultra-high specific surface area, tunable structure, more metal site or unsaturated site, and chemical stability. Over the past decade, different functionalization types of MOFs have been reported in combination with amino acids, nucleic acids, proteins, polymers, and nanoparticles for various applications. In this review, the synthesis and functionalization of MOFs have been thoroughly discussed, and we introduced the existing problems and development trends in these fields. Furthermore, MOFs as advanced adsorbents for selective separation of proteins/peptides are summarized. Additionally, we present a comprehensive prospects and challenges in the preparation of robust functional MOFs-based adsorbents and make a final outlook on their future development prospects in selective separation of proteins/peptides.

Recent Progress on Functional Metal–Organic Frameworks for Supercapacitive Energy Storage Systems

As porous coordination organic polymers, both metal–organic frameworks (MOFs) and their derived materials and MOF‐based composites offer unique organic or inorganic chemistries that display superior features of high specific surface area, accessible active sites, robust structural and chemical diversity, tailorable pore size, exceptional porosity, and pre‐ and postsynthesis structural tunability. Therefore, MOF‐based materials are attractive for energy storage applications, specifically for supercapacitor devices. This review presents recent progress in designing and utilizing pristine MOFs, MOF‐derived nanomaterials, and MOF‐based composite materials for supercapacitors. Most importantly, herein, recent highlights and classifications of electrolytes and their vital role in the structure–property correlation between the structures of MOF‐based materials and suitable electrolyte choices for ideal supercapacitor devices are discussed. Finally, together with a discussion of the progress and outcomes of MOF electrodes, the obstacles and prospects for future MOF‐related research and applications are discussed. To help this intriguing topic continue to advance, this review offers useful insights into the logical design of MOF‐based electrode materials.

Reticular Synthesis of Metal‐Organic Frameworks by 8‐Connected Quadrangular Prism Ligands for Water Harvesting

AbstractUtilization of rigid, highly connected organic linkers is critical for the reticular synthesis of functional metal–organic frameworks (MOFs). However, highly‐stable MOFs (e.g. Al/Cr/Zr‐based MOFs) based on rigid ligands with more than 6 coordinating functions have been rarely achieved thus far. Herein, we describe the construction of two bcu Zr‐based MOFs (named ZrMOF‐1 and ZrMOF‐2) from peripherally extended pentiptycene ligands (H8PEP‐1 and H8PEP‐2) with rigid quadrangular prism shape possessing 8 carboxylic groups at the prism vertices. Particularly, ZrMOF‐1 exhibits microporous structure with large Bruno‐Emmett‐Teller surface area and high water stability, endowing it a promising water harvesting material with a high water uptake capacity of 0.83 gH2O gMOF−1 at P/P0=0.90 and 25 °C, a steep uptake at a low P/P0 of 0.30, and excellent durability over 500 water adsorption‐desorption cycles. Moreover, self‐consistent charge density functional tight‐binding calculations were carried out, rationalizing the water adsorbing process and amount in ZrMOF‐1.

Reticular Synthesis of Metal-Organic Frameworks by 8-Connected Quadrangular Prism Ligands for Water Harvesting.

Utilization of rigid, highly connected organic linkers is critical for the reticular synthesis of functional metal-organic frameworks (MOFs). However, highly-stable MOFs (e.g. Al/Cr/Zr-based MOFs) based on rigid ligands with more than 6 coordinating functions have been rarely achieved thus far. Herein, we describe the construction of two bcu Zr-based MOFs (named ZrMOF-1 and ZrMOF-2) from peripherally extended pentiptycene ligands (H8 PEP-1 and H8 PEP-2) with rigid quadrangular prism shape possessing 8 carboxylic groups at the prism vertices. Particularly, ZrMOF-1 exhibits microporous structure with large Bruno-Emmett-Teller surface area and high water stability, endowing it a promising water harvesting material with a high water uptake capacity of 0.83 gH2O gMOF -1 at P/P0 =0.90 and 25 °C, a steep uptake at a low P/P0 of 0.30, and excellent durability over 500 water adsorption-desorption cycles. Moreover, self-consistent charge density functional tight-binding calculations were carried out, rationalizing the water adsorbing process and amount in ZrMOF-1.

MicroRNA functional metal-organic framework nanocomposite for efficient inhibition of drug-resistant breast cancer cells

MicroRNA functional metal-organic framework nanocomposite for efficient inhibition of drug-resistant breast cancer cells

Conductive Metal-Organic Frameworks with Tunable Dielectric Properties for Boosting Electromagnetic Wave Absorption.

Metal-organic frameworks (MOFs) manifest enormous potential in promoting electromagnetic wave (EMW) absorption thanks to the tailored components, topological structure, and high porosity. Herein, rodlike conductive MOFs (cMOFs) composed of adjustable metal ions of Zn, Cu, Co, or Ni and ligands of hexahydroxytriphenylene (HHTP) are prepared to attain tunable dielectric properties for a tailored EMW absorption. Specifically, the influences of the cMOFs' composition, charge transport characteristic, topological crystalline structure, and anisotropy microstructure on dielectric and EMW absorption performance are ascertained, advancing the understanding of EMW attenuation mechanisms of MOFs. The boosted conductive and polarization losses derived from the conjugation effects and terminal groups, as well as shape anisotropy, lead to a prominent EMW absorption of the cMOFs. The Cu-HHTP confers a minimum reflection loss (RLmin) of -63.55 dB at the thickness of 2.9 mm and a maximum effective absorption bandwidth of 5.2 GHz. Moreover, Zn-HHTP showcases the absorption superiority in the S-band (2-4 GHz) with an RLmin of -62.8 dB at a thickness of 1.9 mm. This work not only hoists the mechanistic understanding of the structure-function relationships for the cMOFs but also offers guidelines for preparing functional MOF materials.

Functionalization of metal-organic frameworks with metallic nanoclusters for ultra-sensitive monitoring of morphine in biological fluids

A reliable, fast, and cost-effective method of monitoring morphine (MO) concentration in biological fluids is highly desired in clinical and modern medicine. Nanotechnology has opened up new possibilities for developing morphine biosensors, but the most advanced electrodes available offer a detection limit (LOD) of ≥10 nM. This work introduces a new, ultrasensitive electrochemical biosensor based on microporous metal-organic frameworks (∼1100 cm2 g−1 surface area) modified by Ag clusters (∼2 nm) and functionalized by Au nanoparticles (∼180 nm). Electrochemical studies show that functionalizing the microporous crystalline particles (620 ± 45 nm) with metal nanoclusters enhances charge transfer kinetics and electrochemical surface area by about 50 and 10 folds, respectively, resulting in high sensitivity (0.127 µA µM−1), broad linear dynamic range (0.05–600 µM), and low LOD (3 ± 0.2 nM). The differential pulse voltammetry confirms the stability (over 6 weeks), repeatability (RSD=3.0%), and reproducibility (RSD=4.0%) of the hybrid biosensor. The decent selectivity and specificity (RSD=7.4%) of the biosensor against various analogs co-existing with MO in urine have also been determined. Therefore, the hybrid metal-inorganic biosensor presents a promising prospect for simple, low-cost, and precise monitoring of biomolecules, including morphine, in biological fluids and clinical medicine.

Detachable MOF-Based Core/Shell Nanoreactor for Cancer Dual-Starvation Therapy With Reversing Glucose and Glutamine Metabolisms.

Tumor-dependent glucose and glutamine metabolisms are essential for maintaining survival, while the accordingly metabolic suppressive therapy is limited by the compensatory metabolism and inefficient delivery efficiency. Herein, a functional metal-organic framework (MOF)-based nanosystem composed of the weakly acidic tumor microenvironment-activated detachable shell and reactive oxygen species (ROS)-responsive disassembledMOF nanoreactor core is designed to co-load glycolysis and glutamine metabolism inhibitors glucose oxidase (GOD) and bis-2-(5-phenylacetmido-1,2,4-thiadiazol-2-yl) ethyl sulfide (BPTES) for tumor dual-starvation therapy. The nanosystem excitingly improves tumor penetration and cellular uptake efficiency via integrating the pH-responsive size reduction and charge reversal and ROS-sensitive MOF disintegration and drug release strategy. Furthermore, the degradation of MOF and cargoes release can be self-amplified via additional self-generation H2 O2 mediated by GOD. Last, the released GOD and BPTES collaboratively cut off the energy supply of tumors and induce significant mitochondrial damage and cell cycle arrest via simultaneous restriction of glycolysis and compensatory glutamine metabolism pathways, consequently realizing the remarkable triple negative breast cancer killing effect in vivo with good biosafety via the dual starvation therapy.

A novel N-heterocyclic carbene-palladium modified metal–organic framework (Sm-MOF-Pd) for Suzuki-Miyaura cross-coupling reaction

A novel 3D Sm-MOF, namely {n[Sm(L)2·2(H2O)]·(Cl)n, H2L+Cl- = 1,3-bis(4-carboxybenzyl)-imidazolium chloride)}, was prepared under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. Then the N-heterocyclic carbene-Pd(II) functionalized metal–organic framework (Sm-MOF-Pd) was yielded by introducing Pd active sites into the Sm-MOF by the post-synthesis modification (PSM) method. This new material was characterized by powder X-ray diffraction (PXRD), thermogravimetric analyses (TGA), scanning electron microscopy (SEM), transmission electron (TEM), energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray photoelectron spectroscopy (XPS) measurements, showing that Pd(II) ions were uniformly dispersed in the Sm-MOF after PSM. The Sm-MOF-Pd reached a catalytic yield of 99 % in Suzuki-Miyaura cross-coupling reactions under optimal reaction conditions. After four cycles, it still maintained high catalytic activity.

Hierarchically ordered macro-mesoporous electrocatalyst with hydrophilic surface for efficient oxygen reduction reaction.

Metal-organic frameworks (MOFs) offer versatile templates/precursors to prepare supported metal catalysts. However, the afforded catalysts usually exhibit microporous structures and unsuitable wettability, which would restrict the accessibility of active sites in liquid-phase reactions. Herein, we develop an etching-functionalization strategy for the construction of a tannic acid-functionalized MOF with a unique hollow-wall and three-dimensional ordered macroporous (H-3DOM) structure. The functional MOF can be further employed as an ideal precursor for the synthesis of cobalt supported on oxygen, nitrogen co-doped carbon composites with H-3DOM structures and hydrophilic surface. The H-3DOM structure can improve the external surface area to maximize the exposure of active sites. Moreover, the oxygen-containing functional groups can enhance the surface wettability to guarantee the external active sites to be more electrochemically accessible in aqueous electrolyte. Benefitting from these outstanding characteristics, H-3DOM-Co/ONC exhibits high electrocatalytic activity in the oxygen reduction reaction, superior to its counterparts without the hierarchically ordered structure and surface functionalization. This article is protected by copyright. All rights reserved.

A bifunctional polycentric-affinity MOF/MXene heterojunction-based molecularly imprinted photoelectrochemical organophosphorus-sensing platform

The analytical functionalization of metal organic frameworks (MOFs) has been an extremely attractive topic in photoelectrochemical (PEC) sensing. However, most PEC sensors based on photoactive MOFs are more focused on the acquisition and amplification of semiconductor photoelectric signals, and the study of affinity mechanisms for specific targets is more limited. Here, we find that PCN-224 (Zn) can effectively sense organophosphorus structures through a multicenter affinity mechanism, as evidenced by x-ray photoelectron spectroscopy (XPS) and computational chemistry. Further, we coupled PCN-224(Zn) to Nb4C3 to form a Schottky junction that enhances the photoelectric signal response of the sensor. In particular, the heterojunction exhibited a higher photocurrent density than pristine PCN-224(Zn) (17.3 μA vs. 26.5 μA cm−2). On the basis, we developed a novel MOF-based polycentric-affinity PEC sensing strategy for dimethoate (DIM) detection in concert with molecular imprinting technology. The affinity effects of the Lewis acidic center sites (Zn(II), Zr(IV)) and spatial matching through molecular imprinting synergistically ensure that DIM is precisely captured. Ultimately, a trace DIM-PEC sensor was constructed by a competitive strategy using dopamine as an electron donor. The photocurrent intensity was linearly related to the logarithm of DIM concentration in the range of 0.1 nM to 1000 nM, with a low detection limit of 26.1 pM (3σ/S). This study demonstrates the potential of bifunctional polycentric-affinity MOF in the PEC sensing.

Smartphone-assisted ratiometric sensing platform for on-site tetracycline determination based on europium functionalized luminescent Zr-MOF

Accurate on-site analysis of tetracycline (TC) is of great research value for ensuring food safety and estimating environmental pollution. Herein, a smartphone-based fluorescent platform for TC detectionhas been developed based on a europium functionalized metal–organic framework (Zr-MOF/Cit-Eu). Based on the inner filter and antenna effect between Zr-MOF/Cit-Eu and TC, the probe exhibited a ratiometric fluorescent response toward TC, resulting in an emission color change from blue to red. Excellent sensing performance was achieved with a detection limit of 3.9 nM, consistent with the linear operation spanning nearly four orders of magnitude. Subsequently, visual test strips based on Zr-MOF/Cit-Eu were prepared, possessing the potential for accurate testing of TC via RGB signals. Finally, the proposed platform was well applied in actual samples with satisfied recoveries (92.27 to 110.22%). This MOF-based on-site fluorescent platform holds great potential on constructing intelligent platform for visual and quantitative detection of organic contaminants.

Functional metal–organic framework nanoparticles loaded with polyphyllin I for targeted tumor therapy

Functional metal–organic framework nanoparticles loaded with polyphyllin I for targeted tumor therapy

Silane-Functionalized Metal-Organic Frameworks for Stimuli-Responsive Drug Delivery Systems: A New Universal Strategy.

A new universal strategy for silane functionalization of metal-organic frameworks (MOFs) was developed. It was demonstrated that silanes were coupled both with terminal hydroxyl (OH) groups and with bridging OH groups of metal-oxo clusters of MOFs through condensation reactions between the silanols of hydrolyzed silanes and the terminal/bridging OH groups to form metal-O-Si bonds. A wide variety of functionalization of MOFs with conventional silanes can be realized by combining synthesis reactions in the solution phase and chemical modifications on the surface. Multivalent supramolecular nanovalves based on the host-guest chemistry of cyclodextrin polymer (CDP) and benzimidazole stalks silanized on the nanoscale MOF (NMOF) surface were successfully constructed. The CDP-valved NMOFs showed the excellent performance of low pH- and α-amylase-responsive controlled drug release. In vitro and in vivo results demonstrated that the CDP-valved NMOFs had a significant inhibitory effect on tumor growth and almost no damage/toxicity to normal tissues. The silanization strategy is universal and opens up a new way for the functionalization of MOFs, which are endowed with a wide variety of applications spanning gas storage, chemical sensing, adsorption and separation, heterogeneous catalysis, and drug delivery.