Metal Organic Framework Cubosomes

Nano-Metal-Organic Frameworks Isolated in Mesoporous Structures

As an alternative to bulk counterparts, metal-organic framework (MOF) nanoparticles isolated within conductive mesoporous carbon matrices are of increasing interest for electrochemical applications. Although promising, a "clean" carbon surface is generally associated with poor compatibility and weak interactions with metal/ligand precursors, which leads to the growth of MOFs with inhomogeneous particle sizes on outer pore walls. Here, a general methodology for in situ synthesis of eight nanoMOF composites within mesochannels with high dispersity and stability are reported. Mesoporous polydopamine (mesoPDA)-F127 nanospheres with unique surface chemistry, e.g., nanoconfined spaces, catechol functional groups, pyrrolic N doping, and hydrophilic PEO blocks, are found to be a suitable molecular platform. Sliced cross-sectional TEM, HAADF-STEM, and corresponding EDS elemental mapping, as well as nitrogen adsorption characterizations, are utilized to visualize the in situ growth process of ZIF-8 nanoparticles. These careful analyses provides direct evidence that the highly dispersed ZIF-8 is exclusively located inside the internal mesochannels. After moderate carbonization of the mesoPDA-F127/ZIF-8 nanocomposites, a prototype for a mesoporous carbon-isolated ZIF-8 nanostructure is achieved, which can regulate Zn2+ plating electrochemistry toward stable aqueous Zn batteries. This is the first report of the complete impregnation and even dispersion of nanoscale MOFs within the interior channels of mesoporous carbons.

Neutral Interface Directed 3D Confined Self-Assembly of Block Copolymer: Anisotropic Patterned Particles with Ordered Structures

Three-dimensional confined self-assembly (3D-CSA) of block copolymers (BCPs) is a distinctive and robust strategy that can yield colloidal polymer particles boasting ordered internal structures and diverse morphologies. The unique advantage of neutral interface lies in its ability to create anisotropic particles with surface patterns. The resulting unique polymer particles exhibit deformability under swelling, coupled with excellent spreadability and optical properties. These particles can also be used for fabrication of anisotropic nanoobjects or mesoporous particles via disassembly or serving as templates. This review comprehensively outlines the research advancements in neutral interface-guided 3D-CSA systems, including surfactant engineering, internal structure control, properties and future possibilities of anisotropic patterned particles.

Assessing the Effect of a Schwarz P Surface on the Oxygen Electroreduction Performance of Porous Single-Atom Catalysts

The surface curvature of catalysts has a decisive impact on their catalytic performance. However, the influence of a negative-Gaussian-curvature surface on the catalytic performance of porous catalysts has remained unexplored due to the lack of suitable samples. Bicontinuous-structured porous structures can serve as ideal models, but they are known as "Plumber's nightmare" due to their highly difficult preparation. Here, using metal-organic frameworks as the precursor and polymer cubosomes as the template, a bicontinuous mesoporous Fe single-atom catalyst (named bmFeSAC) with a Schwarz P surface is synthesized. The bmFeSAC catalyst has a large specific surface area of 916 m2 g-1 and uniformly distributed Fe-N4 active sites with a 1.80 wt.% Fe content. The continuous channels enabled high utilization efficiency of the Fe-N4 catalytic sites, while the negative-Gaussian-curvature surface enabled low reaction energy barrier. As an electrocatalyst of the oxygen reduction reaction, bmFeSAC delivered a high half-wave potential of 0.931 V versus. RHE in alkaline electrolyte, reaching the leading level among those of the reported state-of-the-art electrocatalysts. Furthermore, the bmFeSAC-based Zn-air batteries exhibited excellent performance, demonstrating the potential application of bmFeSAC. This study revealed that a bicontinuous-structured porous structure can improve catalytic activity by increasing the utilization ratio of catalytic sites and, more importantly, by regulating the electronic structure of catalyst surfaces through the negative-Gaussian-curvature.

Coassembling Mesoporous Zeolitic Imidazolate Frameworks by Directed Reticular Chemistry

Conventional microporous zeolitic imidazolate frameworks (ZIFs) face limitations in mass transfer and pore accessibility when dealing with large guest molecules. Here, we describe a technique for the synthesis of mesoporous ZIFs (MesoZIFs) using a strategy we term directed reticular chemistry. MesoZIF-8 was prepared through solvent evaporation-induced coassembly of polystyrene-block-poly(ethylene oxide) (PS-b-PEO), ZIF-8 building blocks, and acetic acid (AcOH), followed by amine-facilitated crystallization of ZIF-8 in the interstices of PS-b-PEO micelles. AcOH prevents the fast coordination of ZIF-8 building blocks, avoiding phase separation during coassembly. The employed amine plays a crucial role in neutralizing the crystallization environment and further deprotonating the 2-methlyimizale linker to coordinate with zinc ions. Ink bottle-shaped mesopores with tunable mesopore sizes were created by adjusting the molecular weight of PS-b-PEO. Compared to microporous ZIF-8, MesoZIF-8 exhibited enhanced performance in Knoevenagel condensation reactions involving large reactants and hydrogen storage capacity. With this study, we establish an efficient approach for synthesizing MesoZIFs with highly accessible mesopores to enhance ZIF performance in targeted applications.

Biphasic interface templated synthesis of wrinkled MOFs for the construction of cascade sensing platform based on the encapsulated gold nanoclusters and enzymes

The design and construction of MOFs with flower-like structure could afford sufficient space for the immobilization of guests with large size and interconnected transport channels for their mass diffusion although it remains a challenge. Herein, wrinkled Ce-based hierarchically porous UiO-66 (Ce-WUiO-66) with good crystallinity was successfully synthesized for the first time using bicontinuous emulsion composed of 1-heptanol, water and F127 (PEO106PPO70PEO106) surfactant as a template. F127 played a key role in the formation of emulsions as a stabilizer, and meanwhile its PEO segments interacted with MOF precursors to guide the evolvement of crystallized pore walls. Through controlling the ratios of heptanol to water and the salinity, the distances of the pleat openings and the morphology of the resultant Ce-WUiO-66 were facilely regulated. In virtue of its highly open radial structure, Ce-WUiO-66 could serve as an ideal platform for loading multiple substances to build a cascade sensing system. As a proof of concept, we designed an amino acid (AA) cascade probe by co-immobilizing gold nanoclusters (AuNCs) and LAA oxidase into Ce-WUiO-66. The aggregation-induced-emission enhancement resulted from the encapsulation of AuNCs into Ce-WUiO-66 significantly improved the detection sensitivity and the detection limit of corresponding substrates reached as low as 10-8 M. The proposed biphasic interface assembly strategy is hopefully to provide a new route for the rational design of MOFs with various open pore structure and broaden their potential applications with multiple large-size substances involved besides the currently exemplified cascade sensing platform.

Polyphenol-Based Bicontinuous Porous Spheres Via Amine-Mediated Polymerization-Induced Fusion Assembly

Bicontinuous porous materials, which possess 3D interconnected network and pore channels facilitating the mass diffusion to the interior of materials, have demonstrated their promising potentials in a large variety of research fields. However, facile construction of such complex and delicate structures is still challenging. Here, an amine-mediated polymerization-induced fusion assembly strategy is reported for synthesizing polyphenol-based bicontinuous porous spheres with various pore structures. Specifically, the fusion of pore-generating template observed by TEM promotes the development of bicontinuous porous networks that are confirmed by 3D reconstruction. Furthermore, the resultant bicontinuous porous carbon particles after pyrolysis, with a diameter of ≈600 nm, a high accessible surface area of 359 m2 g-1, and a large pore size of 40-150 nm manifest enhanced performance toward the catalytic degradation of sulfamethazine in water decontamination. The present study expands the toolbox of interfacial tension-solvent-dependent porous spheres while providing new insight into their structure-property relationships.

Fully Degradable Polyphosphoester Cubosomes for Sustainable Agrochemical Delivery

Microplastic pollution and the urgent need for sustainable agriculture have raised interest in developing degradable carriers for controlled agrochemical release. Porous polymeric particles are particularly promising due to their unique release profiles compared to solid or core-shell carriers. However, creating degradable, mesoporous (2-50 nm) microparticles is challenging, and their potential for agrochemical delivery is largely unexplored. A straightforward self-assembly method is demonstrated for fully degradable porous polymer cubosomes (PCs), showcasing their ability to load and release agrochemicals. Using fully degradable block copolymers (BCPs), poly(ethyl ethylene phosphate)-b-polylactide (PEEP-b-PLA), PCs are synthesized in water with high inner order and open pores averaging 19 ± 3 nm in diameter. During the self-assembly process in the presence of the hydrophobic fungicide tebuconazole, polymersomes transform into PCs by enriching the hydrophobic polymer domain and altering the BCP packing parameter. After self-assemby, highly porous and fungicide-loaded PCs are obtained. Fungicide-loaded PCs show high antimycotic activity against Botrytis cinerea (grey mold), adhere to Vitis vinifera Riesling leaves even after simulated rain, and release the fungicide continuously over several days with different release-kinetics compared to solid particles. PCs hydrolyze completely into lactic acid and phosphate derivatives, highlighting their potential as microplastic-free agrochemical delivery systems for sustainable agriculture.

Coordination-Driven Templated Synthesis of Hierarchically Porous Zeolitic Imidazolate Frameworks for Cascade Enzyme Cycle Amplification Coupled Immunoassay

Although hierarchically porous zeolitic imidazolate frameworks (HPZIFs) not only inherit the intrinsic architectural and chemical stabilities of their microporous counterparts but also afford open space for the efficient mass diffusion of the macromolecules involved, their rational design and construction are still challenging. Herein, HPZIFs with tailorable pore sizes ranging from 18 to 54 nm were successfully fabricated by using a newly developed soft-template-directed strategy. Our success rooted in the fact that the screened PS81-PVP44-PEO113 triblock copolymer could effectively coordinate with the metal precursor for the directed crystallization of ZIFs along surfactant assemblies. The advantages of continuous large pores and open structures in such HPZIFs were fully taken into account to serve as a bioreactor for the efficient immunoassay. The expanded large pores provided not only a significantly vast surface area to enhance the density of capture antibodies but also enough space for accommodating multiple conjugated biomolecules in one pore channel. In combination with a cascade enzyme cycle amplification strategy, a model biomarker of prostate-specific antigen (PSA) at the femtomolar level was checked with a limit of detection of 92 fM using the developed immunosensor. Specific screening on patients with prostate cancer or even benign prostatic hyperplasia was exemplified through accurately quantifying small changes of PSA concentration in clinical serum samples, prefiguring the great potential of the developed HPZIF-8 immunosensor platform for the early monitoring and diagnostics of diseases.

Fe3O4-doped mesoporous carbon cathode with a plumber's nightmare structure for high-performance Li-S batteries

Shuttling of lithium polysulfides and slow redox kinetics seriously limit the rate and cycling performance of lithium-sulfur batteries. In this study, Fe3O4-dopped carbon cubosomes with a plumber's nightmare structure (SP-Fe3O4-C) are prepared as sulfur hosts to construct cathodes with high rate capability and long cycling life for Li-S batteries. Their three-dimensional continuous mesochannels and carbon frameworks, along with the uniformly distributed Fe3O4 particles, enable smooth mass/electron transport, strong polysulfides capture capability, and fast catalytic conversion of the sulfur species. Impressively, the SP-Fe3O4-C cathode exhibits top-level comprehensive performance, with high specific capacity (1303.4 mAh g-1 at 0.2 C), high rate capability (691.8 mAh gFe3O41 at 5 C), and long cycling life (over 1200 cycles). This study demonstrates a unique structure for high-performance Li-S batteries and opens a distinctive avenue for developing multifunctional electrode materials for next-generation energy storage devices.

Photocleavable Polymer Cubosomes: Synthesis, Self-Assembly, and Photorelease

Polymer cubosomes (PCs) are a recent class of self-assembled block copolymer (BCP) microparticles with an accessible periodic channel system. Most reported PCs consist of a polystyrene scaffold, which provides mechanical stability for templating but has a limited intrinsic functionality. Here, we report the synthesis of photocleavable BCPs with compositions suitable for PC formation. We analyze the self-assembly mechanism and study the model release of dyes during irradiation, where the transition of the BCPs from amphiphilic to bishydrophilic causes the rapid disassembly of the PCs. A combination of modeling and experiment shows that the evolution of PCs proceeds first via liquid-liquid phase separation into polymer-rich droplets, followed by microphase separation within this droplet confinement, and finally, membrane reorganization into high internal order. This insight may encourage exploration of alternative preparation strategies to better control the size and homogeneity of PCs.

Engineering Interconnected Open-Porous Particles via Microfluidics Using Bijel Droplets as Structural Templates

Designing porous structures is key in materials science, particularly for separation, catalysis, and cell culture systems. Bicontinuous interfacially jammed emulsion gels represent a unique class of soft matter formed by kinetically arresting the separation of the spinodal decomposition phase, which is stabilized by colloidal particles with neutral wetting. This study introduces a microfluidic technique to create highly interconnected open-porous particles using bijel droplets stabilized with hexadecyltrimethylammonium bromide (CTAB)-modified silica particles. Monodisperse droplets comprising a hydrophobic monomer, water, ethanol, silica particles, and CTAB were initially formed in the microfluidic device. The diffusion of ethanol from these droplets into the continuous cyclohexane phase triggered spinodal decomposition within the droplets. The phase-separated structure within the droplets was stabilized by the CTAB-modified silica particles, and subsequent photopolymerization yielded microparticles with highly interconnected, open pores. Moreover, the influence of the ratio of the CTAB and silica particles, fluid composition, and microchannel direction on the final structure of the microparticles was explored. Our findings indicated that the phase-separated structure of the particles transitioned from oil-in-water to water-in-oil as the CTAB/silica ratio was increased. At intermediate CTAB/silica ratios, microparticles with bicontinuous structures were formed. Regardless of the fluid composition, the pore size of the particles increased with time after phase separation. However, this coarsening was arrested 15 s after droplet formation in the CTAB-modified silica particles, accompanied by a change in the particle shape from spherical to ellipsoidal. In situ observations of the bijel droplet formation revealed that the particle shape deformation is caused by the rolling of elastic bijel droplets at the bottom of the microchannel. As such, the channel setup was altered from horizontal to vertical to prevent the deformation of bijel droplets, resulting in spherical particles with open pores.

Hofmeister Effect Promoted the Introduction of Tunable Large Mesopores in MOFs at Low Temperature for Femtomolar ALP Detection

In addressing the demand for hierarchically mesoporous metal-organic frameworks (HMMOFs) with adjustable large mesopores, a method based on the synergistic effects of low-temperature microemulsions and Hofmeister ions is developed. Low temperature dramatically enhanced the solubility of hydrophobic solvent in the microemulsion core, enlarging the mesopores in HMMOFs replica. Meanwhile, Hofmeister salt-in ions continuously controlled mesopore expansion by modulating the permeability of swelling agent into the microemulsion core. The large mesopores up to 33 nm provided sufficient space for the alkaline phosphatase (ALP) enrichment, and retained the remaining channel to facilitate the free mass diffusion. Leveraging these advantages, a colorimetric sensor is successfully developed using large-mesopore HMMOFs for femtomolar ALP detection based on the enrichment and cycling amplification principles. The sensor exhibited a linear detection range of 100 to 7500 fm and a limit of detection of 42 fm, presenting over 4000 times higher sensitivity than classic para-nitrophenyl phosphate colorimetric methods. Such high sensitivity highlights the importance of adjustable mesoporous structures of HMMOFs in advanced sensing applications, and prefigures their potential for detecting large biomolecules in diagnostics and biomedical research.

Nitrogen-Doped Carbon Cubosomes as an Efficient Electrocatalyst with High Accessibility of Internal Active Sites

Porous carbon particles (PCPs) present considerable potential for applications across a wide range of fields, particularly within the realms of energy and catalysis. The control of their overall morphologies and pore structures has remained a big challenge. Here, using metal-organic frameworks (MOFs) as the precursor and polymer cubosomes (PCs) as the template, nitrogen-doped carbon cubosomes (SP-NCs) with a single primitive bicontinuous architecture are prepared. SP-NCs inherit the high porosity of MOFs, generating a high specific surface area of 825 m2 g-1 and uniformly distributed active sites with a 5.9 at % nitrogen content. Thanks to the presence of three-dimensional continuous mesochannels that enable much higher accessibility of internal active sites over those of their porous counterparts' lack of continuous channels, SP-NCs exhibit superior electrocatalytic performance for oxygen reduction reaction with a half-wave potential of 0.87 V, situating them in the leading level of the reported carbon electrocatalysts. Serving as an air cathode catalyst of the Zn-air battery, SP-NCs exhibit excellent performance, outperforming the commercial Pt/C catalysts.

Ultrahigh-Rate Na/Cl2 Batteries Through Improved Electron and Ion Transport by Heteroatom-Doped Bicontinuous-Structured Carbon

Rechargeable sodium/chlorine (Na/Cl2 ) batteries are emerging candidates for sustainable energy storage owing to their superior energy densities and the high abundance of Na and Cl elements. However, their practical applications have been plagued by the poor rate performance (e.g., a maximum discharge current density of 150 mA g-1 ), as the widely used carbon nanosphere cathodes show both sluggish electron-ion transport and reaction kinetics. Here, by mimicking the sufficient mass and energy transport in a sponge, we report a bicontinuous-structured carbon cubosome with heteroatomic doping, which allows efficient Na+ and electron transport and promotes Cl2 adsorption and conversion, thus unlocking ultrahigh-rate Na/Cl2 batteries, e.g., a maximum discharge current density of 16,000 mA g-1 that is more than two orders of magnitude higher than previous reports. The optimized solid-liquid-gas (carbon-electrolyte-Cl2 ) triple interfaces further contribute to a maximum reversible capacity and cycle life of 2,000 mAh g-1 and 250 cycles, respectively. This study establishes a universal approach for improving the sluggish kinetics of conversion-type battery reactions, and provides a new paradigm to resolve the long-standing dilemma between high energy and power densities in energy storage devices.

Prismatic Block Copolymer Hexosomes

Cubosomes and hexosomes are recent solution morphologies with an ordered porous structure and are observed for lipids and amphiphilic block copolymers (BCPs) with high hydrophobic fractions. Whereas lipid hexosomes typically exhibit a prismatic shape, BCP hexosomes have so far only been observed as closed microspheres where inner channels are not connected to the surrounding medium. Here, we describe the formation of flat, prismatic BCP hexosomes with pronounced faceting and a highly ordered lattice of hexagonally packed channels. We assemble polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP or SV) into the hexosome framework using polystyrene-block-poly(4-vinylpyridine)-block-poly(tert-butyl methacrylate) (PS-b-P4VP-b-PT or SVT) as a macromolecular surfactant in low-χ solvents. During solvent exchange, SV-rich domains form through liquid-liquid phase separation, followed by solidification and confined assembly within these domains. Since the final solvent (acetone) has a very low χ parameter toward PS and P4VP (equaling low interfacial tension), solidification of the hexosome occurs under confinement conditions that we term "supersoft". The low interfacial tension allows the stabilization of the hexagonal-prismatic shape, which originates from the hexagonal lattice of channels. Increasing the interfacial tension with polar cosolvents at some point dominates the particle shape, resulting in deformation of prismatic BCP hexosomes into spinning-top structures. The use of low-χ solvents for confined assembly of BCPs may allow the formation of unusual particle shapes simply by tuning the polymer-solvent interaction.