Self-assembly Of Metal-organic Framework Research Articles

Revealing electrostatic-manipulated self-assembly mechanism helps to readily design enhanced MOF-derived microwave absorbers

The controllable self-assembly of Metal Organic Frameworks (MOFs) crystals plays a vital role in modulating the performance for microwave absorbers. However, most current strategies require colloidal or intricate chemical modifications of nanoparticles, thereby increasing the complexity of structural construction and impeding the broader application of microwave absorbers. To resolve this tough issue, we herein innovatively propose a more easily achievable electrostatic-manipulated self-assembly strategy. By readily manipulating the electrostatic adsorption and repulsion between particles, the aggregation and growth sites of initial MOF crystals are anchored, hence facilitating to the construction of solid-core/shell and hollow porous microstructures for absorbers. The substantial improvement depending on electrostatic effects is clearly observed in experimental results. It demonstrates that the Co@hollow N-doped carbon spheres (Co@HNCSs) absorber, induced by electrostatic repulsion, shows the best overall absorption performance, with a strong absorption of −65.4 dB at a thickness of 1.9 mm and an effective absorption bandwidth (EAB) of 5.4 GHz at a thickness of 1.6 mm, covering almost the entire Ku band. The influence of these strategies on the electromagnetic response mechanisms is further comprehensively discussed. Accordingly, we believe this strategy offers new insights for the MOFs’ structural absorbers via electrostatic-manipulated self-assembly strategy.

Engineered assembly of water-dispersible nanocatalysts enables low-cost and green CO2 capture

Catalytic solvent regeneration has attracted broad interest owing to its potential to reduce energy consumption in CO2 separation, enabling industry to achieve emission reduction targets of the Paris Climate Accord. Despite recent advances, the development of engineered acidic nanocatalysts with unique characteristics remains a challenge. Herein, we establish a strategy to tailor the physicochemical properties of metal-organic frameworks (MOFs) for the synthesis of water-dispersible core-shell nanocatalysts with ease of use. We demonstrate that functionalized nanoclusters (Fe3O4-COOH) effectively induce missing-linker deficiencies and fabricate mesoporosity during the self-assembly of MOFs. Superacid sites are created by introducing chelating sulfates on the uncoordinated metal clusters, providing high proton donation capability. The obtained nanomaterials drastically reduce the energy consumption of CO2 capture by 44.7% using only 0.1 wt.% nanocatalyst, which is a ∽10-fold improvement in efficiency compared to heterogeneous catalysts. This research represents a new avenue for the next generation of advanced nanomaterials in catalytic solvent regeneration.

Self-assembly of metal-organic framework onto nanofibrous mats to enhance proton conductivity for proton exchange membrane

Constructing consecutive proton-conducting nanochannels and optimizing nanophase-separation within proton exchange membrane (PEM) was of guiding significance for improving proton transfer. Metal organic framework (MOF), as a novel and functional material had drawn increasing attention in the research of proton PEM because of its flexible tunability and designability. Herein, a novel MOF-based nanofibrous mats (NFMs) were prepared by the self-assembly of zeolitic imidazole framework-67 (ZIF-67) onto polyacrylonitrile (PAN) NFMs. Subsequently, the ZIF-67 NFMs were incorporated into Nafion matrix to prepare ZIF-67@Nafion composite membrane which aimed at constructing consecutive proton-conducting channels. Especially, the acid–base pairs between N–H (ZIF-67 NFMs) and –SO3H (Nafion) could promote the protonation/deprotonation and subsequent proton leaping via Grotthuss mechanisms. As expected, the ZIF-67@Nafion-5 composite membrane showed a promising proton conductivity of 288 mS/cm at 80 °C and 100% RH, low methanol permeability of 7.98 × 10−7 cm2s−1, and superior power density of 298.68 mW/cm2 at 80 °C and 100% RH. In addition, the resulting composite membrane exhibited considerable enhancement in thermal stability and dimensional stability. This promising strategy provided a valuable reference for designing high-performance PEMs.

Self-Assembly of Metal-Organic Frameworks in Pickering Emulsions Stabilized with Graphene Oxide

Self-Assembly of Metal-Organic Frameworks in Pickering Emulsions Stabilized with Graphene Oxide

Self-Assembly of 0D-2D Heterostructure Electrocatalyst from MOF and MXene for Boosted Lithium Polysulfide Conversion Reaction.

The design of nanostructured electrocatalysts with high activity and long-term durability for the sluggish lithium polysulfide (LiPS) conversion reaction is essential for the development of high-performance lithium-sulfur (Li-S) batteries. Here, the self-assembly of bimetallic selenides on nitrogen-doped MXene (CoZn-Se@N-MX) based on the self-assembly of metal-organic framework and MXene is reported. A combination of 0D CoZn-Se nanoparticles and 2D N-MX nanosheet co-catalysts forms double lithiophilic-sulfifilic binding sites that effectively immobilize and catalytically convert LiPS intermediates. This 0D-2D heterostructure catalyst has a hierarchical porous architecture with a large active area and enables rapid Li ion diffusion, reduces the activation energy of Li2 S deposition, and lowers the energy barrier of Li2 S dissolution. In addition, an assembled CoZn-Se@N-MX hybrid synergistically prevents the aggregation of the CoZn-Se nanoparticles and restacking of the active areas of N-MX nanosheets during assembly and the LiPS conversion process. The Li-S battery with this 0D-2D catalyst delivers excellent rate capability, ultralong cycling life (over 2000 cycles), and a high areal capacity of 6.6 mAh cm-2 with a low electrolyte/sulfur ratio of 5µL mg-1 .

Metal-Directed Assembly of Five 4-Connected MOFs: One-Pot Syntheses of MOF-Derived MxSy@C Composites for Photocatalytic Degradation and Supercapacitors

In this work, a series of divalent metal ions (M = CoII, ZnII, CdII, NiII, and CuII) have been used to react with phthalic acid (H2pa) and 1,4-bis(imidazol-1-yl)benzene (bib) under proper solvethermal conditions, which afforded five metal–organic frameworks (MOFs) with the identical formula [M(pa)(bib)]∞, named Co-, Zn-, Cd-, Ni-, and Cu-MOF, respectively. Co-MOF and Zn-MOF are isoporphous, and present a diamondoid framework. Cd-MOF shows a distorted 2D (4,4) layer just like the herringbone. Ni-MOF and Cu-MOF are also isostructural, and illustrate a 3D CdSO4 net. These topologies are all based on the 4-connected node linked by the ligands pa2- and bib. It is the character of the metal ion that causes the structural diversity, which indicates that the metal ion plays an essential role in the self-assembly of MOFs. Furthermore, five well-dispersed MxSy@C composites have been successfully synthesized through the one-pot sulfurization of MOF precursors, which prevents the sintered phenomenon in the stepwise c...

In Situ Growth of Self-Assembled ZIF-8-Aminoclay Nanocomposites with Enhanced Surface Area and CO2 Uptake.

Self-assembly of metal-organic framework (MOF) nanoparticles (NPs) with a functional material can result in MOF nanocomposites having new and advanced properties along with the fabrication of new nanoscopic structures. However, such assembly of MOFs has not been realized to date. Here we report self-assembled nanocomposites of the zeolitic imidazolate framework (ZIF-8) and layered aminoclay (AC) for the first time, and the ZIF-8@AC composites exhibit significantly enhanced adsorption properties in comparison to those of pristine ZIF-8 nanoparticles. Four different composites denoted as ZIF-8@AC-1, ZIF-8@AC-2, ZIF-8@AC-3, and ZIF-8@AC-4 were synthesized by varying the clay content, and their AC contents were found to be 12.1, 18.3, 22.2, and 27.2 wt %, respectively. The composites were thoroughly characterized by PXRD, FTIR, Raman, and various microscopic techniques (FESEM, TEM, and STEM). The formation of the composites is driven by the specific interaction between unsaturated Zn(II) sites of ZIF-8 nanoparticles and NH2 groups of the aminoclay, which was validated from ζ potential and Raman spectroscopic measurements. The adsorption studies of the desolvated composites were also carried out in detail. The best performance is achieved with one of the composites, which exhibits a 42% increase in BET surface area while CO2 uptake at 298 K is doubled in comparison to the ZIF-8 nanoparticles.

Multi-functional MOF-derived magnetic carbon sponge

Multi-functional magnetic carbon sponge derived from one-step carbonization of self-assembly of metal organic framework and melamine sponge.

MOF-mixed matrix membranes: Precise dispersion of MOF particles with better compatibility via a particle fusion approach for enhanced gas separation properties

Mixed matrix membranes (MMMs) incorporating conventional fillers frequently suffer from insufficient adhesion between the polymer matrix and the fillers. This often results in the formation of non-selective voids at the filler/polymer interface, which decreases the performance of the membrane. A novel approach is presented here to develop metal organic framework (MOF) based MMMs by using the self-assembly of MOF and polymer particles followed by their controlled fusion. MOF-polymer interaction is optimized through this strategy and it overcomes MOF-polymer incompatibility, MOF agglomeration and MOF distribution problems, happening especially at high loadings of MOFs when applying conventional methods. Matrimid® polymer particles were first prepared by precipitating a Matrimid® polymer solution in water. The surface of these particles was then modified by the introduction of imidazole groups, enhancing the chemical compatibility with the selected ZIF-8 MOF. ZIF-8 nanoparticles were then grown in-situ to this modified polymer particle suspension by addition of the precursor for ZIF-8 synthesis. The resulted suspension was cast to dryness and annealed in a solvent–vapor environment to induce particle fusion, leading to a dense MMM structure. Scanning electron microscopy (SEM) images showed an excellent dispersion of the ZIF-8 nanoparticles forming a percolating pathway without any agglomeration, even at 40wt% loading of the ZIF-8. Excellent dispersion of ZIF-8 and an excellent ZIF-8-polymer interfacial adhesion resulted in a significant improvement in both CO2 permeability and CO2/CH4 selectivity. The CO2 permeability of the MMMs increased by 200% and the CO2/CH4 selectivity increased by 65% as compared to unfilled Matrimid®. More detailed analysis of the gas transport performance of the MMMs showed that the CO2 permeability and the CO2/CH4 selectivity are mainly governed by the increase in CO2 diffusivity. The presented approach is a very versatile MMM preparation route, not only for this specific ZIF and polymer but for a wide range of material combinations.

Magnetic cobalt–graphene nanocomposite derived from self-assembly of MOFs with graphene oxide as an activator for peroxymonosulfate

While metal organic frameworks (MOFs) have been extensively explored as a platform for developing porous metal oxides, another intriguing direction is to use MOFs as precursors to prepare carbonaceous materials.

Unusual six-connected self-catenated network with 5-fold interpenetrated CdSO4subnets: stepwise synthesis, topology analysis and fluorescence properties

In this work, the rod-like ligand 4,4′-bis(imidazol-1-yl)-biphenyl (L) has been utilized as a long building block to perform an intensive study on the entanglement of metal–organic frameworks (MOFs). The room-temperature reaction of Cd(ClO4)2·6H2O with ligand L in a glass-tube affords a new coordination polymer {[Cd(ClO4)2(L)2]·(CH3OH)·(H2O}∞ (1), which exhibits an inter-digitated (4,4) layer pierced by the ClO4− ion. Considering the weak coordination affinity of the ClO4− ion and that it could be easily replaced by other ions, complex 1 was employed as a precursor to react with NH4Cl, resulting in a novel organic–inorganic hybrid material {[CdCl(L)2](ClO4)·(H2O)5.5·(CH3OH)0.5}∞ (2). In complex 2, the heteroleptic octahedral CdII node is connected by the linear spacer L into a five-fold interpenetrated CdSO4 framework. Then, the subnet is further linked together by the Cl− ion to form an unusual self-catenated network with the Schafli symbol of 44·610·8. Great structural diversities in 1 and 2 reveal that the counterion plays an important role in the self-assembly of MOFs. Furthermore, complexes 1 and 2 both exhibit solid-state fluorescence properties at room temperature.

Urothermal synthesis of a photoluminescent zinc coordination polymer

Abstract Solvent plays an important role in the self-assembly of metal-organic frameworks (MOFs). It has been demonstrated that the urea derivatives are a new kind of useful solvents, and a new synthetic method denoted as “urothermal synthesis” is emerging. Presented here are the urothermal synthesis, structure and photoluminescent property of an interesting coordination polymer {Zn3[(sip)2(tmdpy)2(e-urea)4(H2O)2](e-urea)2}n (1; sip = 5-sulfoisophthalate; tmdpy = 1.3-di(4-pyridyl)propane; and e-urea = 2-imidazolidinone) with ladder-like structure.

Supramolecular association of water molecules forming discrete clusters in the voids of coordination polymers

The fundamental importance of water in many biological, chemical and physical processes has prompted enormous curiosity for this liquid from theoreticians and experimentalists alike. However, water is not a simple liquid and many of its properties are considered anomalous. Hydrogen bonding interactions, their fluctuations and rearrangement dynamics determine the properties of liquid water. A major obstacle to understand this liquid is a correct description of the cooperative nature of H-bonding among a collection of water molecules. The key here is precise structural data of various hydrogen-bonded networks of water clusters in different restricted environments. How discrete water clusters assume structures that are different from the gas phase structures based on theoretical studies can throw light on the effect of environments on the H-bonded networks of this liquid. Besides, the degree of structuring of a water cluster that can be imposed by its environments and vice versa, can be of importance in the self-assembly of metal-organic frameworks. This review deals with the study of discrete water clusters present in metal-organic framework structures.