Morphology Of Metal-organic Frameworks Research Articles

Customization of indium-based MOFs for enhanced adsorptive and photocatalytic of organic pollutants: Morphology involvement on performance and mechanism

Metal-organic frameworks (MOFs) as photocatalysts are promising candidates for environmental wastewater treatment owing to their tunable crystal structure, well-ordered donor–acceptor interface, and exceptional porosity. However, precise control over size and morphologies of MOFs to enhance adsorptive and photocatalytic performance is still a considerable challenge. Herein, the MIL-68(In)–NH2 (MN) MOFs with special acicular structure are customized by a facile method, in which the growth of crystal nuclei is inhibited and regulated by pyridine. The formation mechanism of MN with different morphologies and size is introduced, and their photocatalytic activities are systematically explored by degrading model pollutants tetracycline (TC) and dyes under visible light irradiation. Benefiting from its high specific surface area and the exposed large lattice spacing facet, the wool-ball morphology MN (MN-W) with surface acicular nanostructure presents an optimum photocatalytic performance compared to other MN morphologies. The MN-W also exhibits excellent adsorption capacity, remarkable cyclic stability, and good practical organic wastewater treatment capability. The possible photodegradation mechanism and pathways are elucidated, demonstrating that h+ is the primary reactive species, followed by •OH and •O2– radicals, responsible for the degradation of TC. This work is anticipated to tailoring design and modulate MOF photocatalysts for boosting the photocatalytic performance towards organic effluents remediation.

Tuning Morphologies of Metal-Organic Framework-Derived Ni3P/Ni Carbon Nanocomposites for Water Oxidation.

The oxygen evolution reaction (OER) frequently acts as a kinetic bottleneck in various energy storage and conversion systems. Effective electrocatalysts for the OER play a crucial role in reducing the reaction barrier and expediting the reaction. Multicomponent transition metal phosphides (TMPs) have garnered an extensive amount of attention as a result of their exceptional performance in the OER. Here, we present a direct method for preparing two intrinsic morphologies of metal-organic frameworks (MOFs), barrel-like BMM-10 and pancake-like BMM-10(Ac), achieved by establishing a protonation/deprotonation equilibrium with varying NO3-/Ac- ratios. The BMM-10(Ac)-C catalyst was synthesized via heat treatment of the BMM-10(Ac) precursor, exhibiting superior OER performance. It realized an overpotential of 286 mV at a current density of 10 mA cm-2, with a Tafel slope of 111.17 mV decade-1 and a current retention of 98.03%. This improvement arises from the synergistic interaction between Ni3P/Ni nanoparticles and the partially graphitic carbon layer, augmenting the exposure of active sites. Furthermore, alterations in the morphological features of MOF-derived Ni3P/Ni carbon nanocomposites adjusted the active electrochemical surface area, thereby modulating the overall OER performance of the corresponding TMP carbon nanocomposites. This methodology can be extended to control the morphology of other MOFs and their derivatives, providing innovative avenues for the design and synthesis of new MOF-based TMP nanomaterials.

Morphology Control of Zr-Based Luminescent Metal-Organic Frameworks for Aflatoxin B1 Detection.

Metal-organic frameworks (MOFs) have gained significant prominence as sensing materials owing to their unique properties. However, understanding the correlation between the morphology, properties, and sensing performance in these MOF-based sensors remains a challenge, limiting their applications and potential for improvement. In this study, Zr-MOF was chosen as an ideal model to explore the impact of the MOF morphology on the sensing performance, given its remarkable stability and structural variability. Three luminescent MOFs (namely rod-like Zr-LMOF, prismoid-like Zr-LMOF, and ellipsoid-like Zr-LMOF) were synthesized by adjusting the quantities of the benzoic acid and the reaction time. More importantly, the sensing performance of these Zr-LMOFs in response to aflatoxin B1 (AFB1) was thoroughly examined. Notably, the ellipsoid-like Zr-LMOF exhibited significantly higher sensitivity compared to other Zr-LMOFs, attributed to its large specific surface area and pore volume. Additionally, an in-depth investigation into the detection mechanism of AFB1 by Zr-LMOFs was conducted. Building upon these insights, a ratiometric fluorescence sensor was developed by coordinating Eu3+ with ellipsoid-like Zr-LMOF, achieving a remarkably lower detection limit of 2.82 nM for AFB1. This study contributes to an improved comprehension of the relationship between the MOF morphology and the sensing characteristics while presenting an effective approach for AFB1 detection.

Microflower-like Fe-Co-MOF with enhanced catalytic performance for decomposition of ammonium perchlorate and combustion of ammonium perchlorate-based composite propellants

Ammonium perchlorate (AP) serves as a crucial component in solid propellants. Enhancing its thermal decomposition with catalysts improves the combustion performance of solid propellants significantly. To enhance the catalytic performance of metal-organic frameworks (MOFs) on AP, this study controlled the morphology of MOFs by adding metal atoms, resulting in a Fe-Co-MOF catalyst with higher specific surface area and dual-metal synergistic effect. The catalytic effect of the catalyst on AP was investigated using DSC and TG-IR, followed by studying its influence on the combustion performance of AP-based composite propellants. The results show that the introduction of 5% Fe-Co-MOF reduced the decomposition temperature of AP to 298.6 °C, decreased the activation energy to 151.6 kJ mol-1, and increased the heat release by 110.6%. Additionally, the ignition delay of the propellant decreased by 71 ms, and the combustion rate increased by 43.8%. Mechanistic studies demonstrate that the abundant catalytic sites and oxygen vacancies of Fe-Co-MOF facilitate the charge transfer rate during the AP thermal decomposition process and promote the increase in AP heat release by suppressing the high-temperature conversion of N2O. This research paves the way for enhancing the application of MOF materials in AP-based solid propellants.

In situ Synthesis of Single Layered Metal-Organic Frameworks via Inkjet Printing on a Cellulose Nanofiber Film.

The inkjet printing is a simple method to develop pattern-controlled 2D metal-organic frameworks (MOFs) due to its cost-effectiveness and ease of operation. Despite the sophisticated structures of MOF crystals, the MOF surfaces are easily contaminated by the adsorption of an ink solution, and the printing nozzle can be clogged by the aggregates of MOFs during printing. Unlike the mixture inks of MOFs and a carrier medium, the surface-specific patterning by in situ synthesis provides the film surface with the controlled patterns of an MOF single layer having different morphologies of MOFs without changing the ink cartridges. It enables facile printing due to the low viscosity of inks and escapes the risk of nozzle clogging because MOFs are synthesized at the printed patterns on the substrates. The ion-exchanged cellulose nanofiber (CNF) films form strong coordination with metal ions enhancing the stability of the MOFs on the film surface. It also demonstrates the controlled coverage of the MOFs by the printing pass number and the carboxylate content of CNF and the tunable adsorption of the guest molecules for different loading capacities of the printed patterns.

Mixed matrix membranes (MMMs) with amine-functionalized ZIF-L for enhanced CO2 separation performance

Amine-functionalized Metal-Organic Frameworks (MOFs) stand out as highly promising materials in membrane separation technology. Nevertheless, the incorporation of amine-functionalized additives may lead to uncontrollable alterations in MOF morphology. Two intact blade-like MOFs (PEI (Polyethylenimine)-ZIF-L and PAMAM (Polyamidoamine)-ZIF-L) were successfully synthesized by controlling the conditions and then introduced into Pebax 2533 to fabricate Mixed Matrix Membranes (MMMs). Hydrogen bonding and other interactions with Pebax can be formed by PEI-ZIF-L and PAMAM-ZIF-L to enhance interfacial compatibility. Simultaneously, a reversible reaction with CO2 molecules can be undergone by the amine groups, resulting in facilitated transport in MMMs. The CO2 separation performance of the MMMs is enhanced by this process, with the facilitation being more pronounced under humid conditions. Under humid conditions, the CO2 permeabilities of Pebax-PEI-ZIF-L (2 wt%) and Pebax-PAMAM-ZIF-L (2 wt%) MMMs were 639.4 Barrer and 702.7 Barrer, respectively, while the CO2/N2 selectivities were 26.68 and 24.35, respectively. Both permeability and selectivity exhibited a significant increase of 200% and 130%, respectively, compared to pure Pebax. Furthermore, the MMMs demonstrated excellent long-term stability during 72 h of continuous operation in a humid environment, showcasing significant potential for industrial applications, particularly in humid flue gas carbon capture.

M-Ni-Co MOF (M=Zn, Fe, Mn) for high-performance supercapacitors by adjusting its morphology

Metal-organic frameworks (MOF) have been wildly synthesised and studied as electrode materials for supercapacitors, and bimetallic MOF of Ni and Co has been broadly studied to enhance both specific capacitance and stability of supercapacitors. Herein, a best performance (about 320 F/g) of Ni–Co bimetallic MOF was found in a uniform preparation condition by adjusting the ratio of Ni to Co. Then tiny third metal ion was introduced, and we found that the morphology of material has a significant change on the original basis. Furthermore, certain ions (Zn, Fe, Mn) introduced make a huge improvement in capacitance based on Ni–Co MOF of 320 F/g. The result shows that Zn–Ni–Co MOF, Fe–Ni–Co MOF and Mn–Ni–Co MOF perform specific capacitance of 1135 F/g, 870 F/g and 760F/g at 1 A/g, respectively. Meanwhile, the asymmetric supercapacitor (ASC) was constructed by Zn–Ni–Co MOF as positive electrode and active carbon (AC) as negative electrode. The Zn–Ni–Co MOF//AC ASC possesses a energy density of 58 Wh/kg at a power density of 775 W/kg. This research provides a new methods to regulate the morphology of MOF and a novel viewpoint for assembling high-performance, low-price, and eco-friendly green energy storage devices.

Room temperature synthesized layered CAU-17 MOFs for highly active and selective electrocatalytic CO2 reduction to formate

Modulating the morphology of metal-organic frameworks (MOFs) has been identified as an effective strategy for enhancing the electrocatalytic performance of CO2 reduction reactions (CO2RR). In this study, CAU-17 MOFs ([Bi(BTC)(H2O)]·2 H2O·MeOH) were prepared via a sonication-assisted method at room temperature, which is considered a simpler technique compared to the conventional hydrothermal method. Additionally, the morphology of CAU-17 MOFs was further regulated by incorporating a rare-earth metal (La), resulting in the observation of two distinct structures, i.e. CAU-17 hexagonal prism (CAU-17-HP) and CAU-17 layer (CAU-17-Layer). Compared to CAU-17-HP, CAU-17-Layer exhibits an excellent selectivity towards formate with the maximum Faradaic efficiency of 95.5% at − 1.1 VRHE in an H-cell. Subsequently, the limited catalytic activity of CAU-17-Layer was boosted by anchoring nano CeO2 onto its surfaces (CeO2 @CAU-17-Layer). The as-prepared composite catalyst demonstrated outstanding performance in the conversion of CO2 to formate, with a current density surpassing − 100 mA cm-2 at potentials more negative than − 1.0 VRHE and reaching − 200 mA cm-2 at − 1.5 VRHE in a flow cell. This study demonstrates the significant potential of morphology-engineered and rare-earth metals composited MOFs in facilitating highly efficient reduction of CO2.

Metal-Organic Framework as a New Type of Magnetothermally-Triggered On-Demand Release Carrier.

The development of external stimuli-controlled payload systems has been sought after with increasing interest toward magnetothermally-triggered drug release (MTDR) carriers due to their non-invasive features. However, current MTDR carriers present several limitations, such as poor heating efficiency caused by the aggregation of iron oxide nanoparticles (IONPs) or the presence of antiferromagnetic phases which affect their efficiency. Herein, a novel MTDR carrier is developed using a controlled encapsulation method that fully fixes and confines IONPs of various sizes within the metal-organic frameworks (MOFs). This novel carrier preserves the MOF's morphology, porosity, and IONP segregation, while enhances heating efficiency through the oxidation of antiferromagnetic phases in IONPs during encapsulation. It also features a magnetothermally-responsive nanobrush that is stimulated by an alternating magnetic field to enable on-demand drug release. The novel carrier shows improved heating, which has potential applications as contrast agents and for combined chemo and magnetic hyperthermia therapy. It holds a great promise for magneto-thermally modulated drug dosing at tumor sites, making it an exciting avenue for cancer treatment.

Synthesis of Hollow Leaf-Shaped Iron-Doped Nickel–Cobalt Layered Double Hydroxides Using Two-Dimensional (2D) Zeolitic Imidazolate Framework Catalyzing Oxygen Evolution Reaction

Layered double hydroxides (LDHs) have been reported as one of the most effective materials for oxygen evolution reaction (OER) catalysts, which are prone to hydrolysis and oxidation under OER conditions. Metal–organic frameworks (MOFs) are porous materials with high crystallinity and internal surface area. The design of LDHs based on MOFs has attracted increasing attention owing to their high surface area, exposed catalysis sites, and fast charge/mass transport kinetics. Herein, we report a novel approach to fabricate a leaf-shaped iron-doped nickel–cobalt LDH (L-Fe-NiCoLDH) derived from a two-dimensional (2D) zeolitic imidazolate framework with a leaf-like morphology (ZIFL). Iron doping played a significant role in enhancing the specific surface area, affecting the OER performance. L-Fe-NiCoLDH showed high OER performance with an overpotential of 243 mV at 10 mA cm−2 and high durability after 20 h. The design of LDHs based on the leaf morphology of MOFs offers tremendous potential for improving OER efficiency.

Ionic Liquid Meets MOF: A Facile Method to Optimize the Structure of CoSe2-NiSe2 Heterojunctions with N, P, and F Triple-Doped Carbon Using Ionic Liquid for Efficient Hydrogen Evolution and Flexible Supercapacitors.

The rational design of catalysts' spatial structure is vitally important to boost catalytic performance by exposing the active sites and increasing specific surface area. Herein, the heteroatom doping and morphology of CoNi metal-organic frameworks(MOF) are modulated by controlling the volume of ionic liquid used in synthesis and generating CoSe2 -NiSe2 heterojunction structures wrapped by N, P, F tri-doped carbon(NPFC) after a selenisation process. Notably, the unique cubic porous structure of CoSe2 -NiSe2 /NPFC results in a specific surface five times that of the sheet-like hollow structure produced without ionic liquid. Moreover, the charge redistribution during heterojunction formation is verified in detail using synchrotron radiation. Density functional theory calculations reveal that the formation of heterojunctions and doping of heteroatoms successfully lower the ΔGH* and ΔGOH* values. Consequently, CoSe2 -NiSe2 /NPFC exhibits excellent activity for HER in both acidic and alkaline solutions. Meanwhile, CoSe2 -NiSe2 /NPFC as a cathode material exhibits excellent performance in a flexible solid-state supercapacitor, with a superior energy density of 55.7Wh kg-1 at an extremely high-power density of 15.9kW kg-1 . This material design provides new ideas for not only using ionic liquids to modulate the morphology of MOFs but also deriving heterojunctions and heteroatom-doped carbon from MOFs.

Glyco-conjugated metal-organic framework biosensor for fluorescent detection of bacteria.

Metal-organic frameworks (MOFs) are hybrid materials constructed by the linkage between an inorganic secondary building unit and an organic linker. A number of MOFs are luminescent in nature and can be structurally tuned for desirable geometry, surface functionality, and porosity. Luminescent MOFs have been endorsed for various biosensing applications. Lectins and carbohydrates have been used for the development of simple and convenient biosensing and bioimaging tools. Lectins are mostly present on the surface of microorganisms where they aid in pathogenesis. Due to this, they can be potential targets for a microbial biosensor. The present study, for the first time, explores the usage of a carbohydrate-conjugated FeMOF (Glyco-MOF) bioprobe for the selective determination of Pseudomonas aeruginosa and Escherichia coli. NH2-MIL-53(Fe) MOF was synthesized via a room temperature protocol and separately conjugated with galactose and mannose sugars via glutaraldehyde chemistry. The synthesized bioprobe is validated for structural integrity, luminescent nature, stability, and analyte assay. Electron microscopy studies validated the unhindered MOF's morphology and structural integrity, after bioconjugation. The synthesized bioprobes were able to detect P. aeruginosa and E. coli up to respective detection limits of 202 and 8CFU/mL, respectively. The bioprobes are selective even in co-presence of possible interferants as well as being environmentally stable.

The influence of solvent controlled morphology on capacitive properties of metal-organic frameworks based on polyaminocarboxybenzene ligands

In order to overcome the low capacitive performance of traditional metal organic frameworks (MOFs) applied to supercapacitors, a novel conjugated small molecule monomer(3,5-diaminobenzoic acid, DABA) with amino and carboxyl groups was used as a ligand, and Ni and Co ions as metal nodes to construct novel highly electroactive bimetallic MOF(DABA-MOF) materials through a simple one-step solvothermal method. The structure and capacitive performance of obtained DABA-MOF in three organic solvents with different polarities and degrees of deprotonation (methanol, ethanol, N,N-dimethylformamide) was investigated, and it was found that with the increase of solvent deprotonation degree, the morphology of DABA-MOF with the coexistence of amino and carboxyl groups gradually changes from a smooth rod-shaped solid structure to a rough hydrangea-like structure, and the corresponding capacitive performance of DABA-MOF is also gradually enhanced. In particular, DABA-MOF synthesized in DMF can reach a maximum specific capacitance of 621 C g−1 at 1 A g−1, and the capacitance remains as high as 81.05% even after 5000 cycles, which exhibit excellent capacitance properties. This study shows that it has potential advantages to select the mixed coordination active MOF with amino and carboxyl groups as the electrode material for supercapacitor, and the deprotonation degree of solvent has a great influence on the structure and morphology of MOF with mixed active coordination sites.

Highly effective detection of picric acid by a Ca(II)-Framework with adjustable crystal morphology and size

It is of great significance to synthesize photo-functional metal-organic frameworks (MOFs) for specific identification of pollutants and to control the morphology of MOFs for practical applications. In this article, a Ca(II)-organic framework [HBU-170, H3L ​= ​4, 4′, 4'' - (1H-imidazole-2, 4, 5-triyl) tribenzoic acid] with controllable morphology and size, was successfully synthesized under solvothermal conditions by regulating pH and characterized. With the decrease of pH value, the size of crystals is getting larger and the appearance changes from spherical to the flowers “blossomed” gradually. For the best crystallinity and better thermal stability, HBU-170–25 was selected as the volunteer for fluorescent detections. To investigate the concentration effect of detection, two groups of nitro aromatic compounds are used as additive agent. The most striking properties of HBU-170–25 are the distinct red shift and fluorescence changes observed in the presence of picric acid. The limit of detection (LOD) is calculated to be 19.06 ​μM (based on the linear regression in the range of 65.420–310.345 ​μM). The fluorescence quenching rates of picric acid is 6.7 × 103 in the linear range of 65.420–310.345 ​μM. According to the quenching efficiency, HBU-170–25 represents the better detection ability in the lower concentration. Moreover, the results of actual sample analysis indicate that HBU-170–25 owns the potential of application in the tests of actual samples.

Effects of Acid Modulators on the Microwave-Assisted Synthesis of Cr/Sn Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) have attracted remarkable attention for their distinguished structural designability. Precisely controlling the particle size and improving the structural stability of MOF nanoparticles influence their catalytic activity significantly. In this study, six acids (nitric, hydrochloric, formic, acetic, succinic, and citric acids) were used as modulators to prepare bimetallic MIL-101 (Cr, Sn) (MIL stands for Materials of Institut Lavoisier) via a microwave-assisted hydrothermal method. Changes in volumetric, structural, stability, and catalytic properties, size, and shape of MIL-101 (Cr, Sn) were examined using scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, and N2 adsorption–desorption measurements. All modulators altered the MOF properties. Compared with other samples, acetic acid as a modulator mildly altered the MOF morphology by narrowing their particle size distribution, enhancing the specific surface area, and significantly improving their water and thermal stabilities. The addition of acetic acid was suitable for the catalytic conversion of glucose to 5-hydroxymethylfurfural (5-HMF), achieving a 43.1% 5-HMF yield with 91.4% glucose conversion in a mixed solution of γ-valerolactone and saturated salt water at 150 °C after 30 min.

The challenges and promises of layered 2D perovskites

Dr. Tsai is a postdoctoral associate at the University of California, Berkeley, and works with Prof. Jeffrey Long on controlling the crystal growth kinetics and morphology of metal-organic frameworks (MOFs) for CO₂ capture. After earning a BS degree in chemistry (Fu Jen Catholic University) and MS degree in polymer science (National Taipei University of Technology), he continued to work at Los Alamos National Laboratory in polymer thin-film research for sensors and catalysis. He continued his PhD training in material science and nanoengineering at Rice University, where he focused on the development of 2D perovskite materials and device research for applications in photovoltaics, light-emitting diodes, and radiation detectors.

3D juniperus sabina-like Ni/Co metal-organic framework as an enhanced electrode material for supercapacitors

Metal-organic frameworks (MOFs) haves been intensively studied as active electrode materials for supercapacitors. However, few studies have been systematically investigated the electrochemical performance of MOFs as electrode materials by adjusting the raw material components and reaction conditions to regulate and control MOFs morphology structures. Herein, a series of nickel/cobalt MOFs (Ni/Co-MOFs) with different morphology structures were synthesized by one-pot solvothermal method via adjusting raw material components and reaction conditions. Results show that three-dimensional (3D) juniperus sabina-like Ni/Co-MOF has optimal electrochemical performance with a specific capacitance of 982.5 ​F/g at 0.5 A/g. Meanwhile, the asymmetric supercapacitor exhibits the capacitance of 132.0 ​F/g at 0.5 A/g, and the corresponding energy density and power density are 46.9 ​Wh/kg and 400.0 ​W/kg, respectively. The work presents a novel strategy to regulate and control the morphology structures of MOFs by adjusting the raw material components and reaction conditions to achieve the optimal electrochemical performance of MOFs.

A truncated octahedron metal-organic framework derived TiO2@C@MoS2 composite with superior lithium-ion storage properties

Metal-organic frameworks (MOFs), as 3D porous precursors, have demonstrated great potential as electrode materials for lithium storage on account of high specific area and tunable structure. To enhance the intrinsic performance and endow MOFs with versatility, constructing distinctive morphology of MOFs while maintaining their porous structure to satisfy various application is highly desirable. Herein, we successfully developed a facile strategy for rationally designing and synthesizing the morphology of MOFs from circular plate shape to truncated octahedron gem shape via regulating the ratio of Pluronic F127 to terephthalic acid. In addition, the as-prepared Pluronic F127-regulated Ti-based MOFs (F-MIL-125-Ti) sacrifice as precursor to derive 3D mesoporous titanium dioxide (TiO 2 ) and as template for in situ growth of molybdenum disulfide (MoS 2 ) nanosheets to prepare a truncated octahedron TiO 2 @C@MoS 2 hierarchical composite. As expected, the distinctive 3D hierarchical TiO 2 @C@MoS 2 electrode exhibits superb rate capability (775 mAh g −1 at 5 C) and outstanding cycling stability (822 mAh g −1 after 1000 cycles at 1 C), which is benefiting from the 3D mesoporous TiO 2 and synergies between TiO 2 and MoS 2 nanosheets. This work develops new insight to design novel and controllable morphology MOFs-derived materials for application of energy storage devices. We fabricated 3D hierarchical MOF-derived TiO 2 @C@MoS 2 composite with unique truncated octahedron morphology for the first time. The as-prepared composite exhibits superb specific capacity and cycling stability as Li-ion battery anode material. • The morphology evolution of metal-organic frameworks via different additive dosage. • The synergy effects between nanosheets and truncated octahedron materials. • The hierarchical porous composite electrode with enhanced electrochemical performance. • TiO 2 @C@MoS 2 delivered 1180 mAh g −1 at 0.1 C.

Nanospace Engineering of Metal‐Organic Frameworks for Heterogeneous Catalysis

AbstractThe structural advantages of metal‐organic frameworks (MOFs) can facilitate wide applications in the field of catalysis, including oxidation, hydrogenation, acetalization, transesterification, catalytic cracking, and so on. The efficiency of catalysis is closely related to the synergy between active center, auxiliary center, and microenvironment. Researchers can customize MOFs according to the needs of catalytic reactions, and many strategies were established for boosting catalytic performance. In this review, we aim to summarize and illustrate recent progress in the nanospace engineering of MOFs. Generally, MOFs were engineered mainly from the following aspects: 1) Regulation of pore size, including micropores, mesopores, and macropores. 2) Engineering of encapsulated active species, such as metal nanoparticles, quantum dots, polyoxometalates, enzymes, etc. 3) Engineering of MOFs morphology from zero dimension to three‐dimension. 4) Controllable integration of MOFs with multi‐strategies. 5) Construction of multivariate MOFs via introducing multiple or mixed organic functional groups into the existing framework. Besides, for further low cost and practical applications, challenges for MOFs as green and sustainable catalysts are also discussed.

Chitosan-assisted MOFs dispersion via covalent bonding interaction toward highly efficient removal of heavy metal ions from wastewater

Metal organic frameworks (MOFs) have been considered to be robust adsorbent for the removing heavy metal ions from wastewater due to their unique properties such as large active sites, high specific surface area and high porosity, etc., however, their practical engineering application faces the problem of serious agglomeration. In this work, a new strategy of chitosan (CS) assisting MOF dispersion was proposed to develop the new generation of MOF-based adsorbents, namely, CS grafted UiO-66-NH2 composite materials (CGUNCM). The UiO-66-NH2 was selected and it was grafted onto the main chains of CS through covalent bonding interaction with the aid of glutaraldehyde, which was totally different from the common method that grafting molecular chains on the surface of MOFs resulting in the dramatic reduction of active adsorption sites. The results show that grafting MOFs onto CS main chains not only greatly improves the dispersion of MOFs but also reserves the morphology of MOFs as much as possible. The adsorption performances toward Cu(II) and Pb(II) were intensively studied by varying adsorbate concentration, ionic strength, the contact time, adsorption temperature and pH value of solution. The results show that the composite adsorbent exhibits high adsorption efficiency and the adsorption equilibrium can be reached within 45 min, and the maximum adsorption capacity toward Cu(II) and Pb(II) achieve 364.96 mg/g and 555.56 mg/g, respectively. Furthermore, the composite adsorbent shows good reusability. This work provides a new method of fabricating the MOF-based adsorbent and paves the way for the practical application of such adsorbents in wastewater treatment.