Porous Superstructures Research Articles

Biomimetic Hierarchies for Universal Surface Enhancement and Applications in Water Treatment.

Hierarchical superstructures, ubiquitously found in nature, offer enhanced efficiency in both substance reaction and mass transport owing to their unique multiscale features. Inspired by these natural systems, this research reports a general and scalable electrochemical scheme for creating highly branched, multilevel porous superstructures on various electrically conductive substrates. These structures exhibit cascading features from centimeters, submillimeters, micrometers, down to sub-100 nm, significantly increasing the surface area of substrates, such as foams, foils, and carbon cloth by 2 orders of magnitude─among the highest reported enhancements. This versatile and low-cost method, applicable to a range of electrically conductive substrates, enables innovative flow-assisted water purification with enhanced energy efficiency. The performance, successfully removing 99% of mercury within 0.5 h at 540 rpm and meeting the U.S. Environmental Protection Agency (EPA) safety standards for drinking water, further validates the advantages of these unique structures. Overall, the reported general, economical, and versatile scheme could broadly impact energy and environmental remediation.

A Simple and Sequential Strategy for the Introduction of Complexity and Hierarchy in Hydrogen-Bonded Organic Framework (HOF) Crystals for Environmental Applications.

Hydrogen-bonded organic frameworks (HOFs) are a new class of crystalline porous organic molecular materials (POMMs) with great potential for a diverse range of applications. HOFs face common challenges to POMMs, and in general to purely organic crystals, that is, the difficulty of integrating complexity in crystals. Herein, we propose a simple and sequential strategy for the formation of HOFs with hierarchical superstructures. The strategy is based on controlling the assembly conditions, avoiding the use of any surface functionalization or template, which allows to obtain hierarchical crystalline porous superstructures in an easy manner. As proof of concept, we obtained the first example of core-shell (HOF-on-HOF) crystals and HOFs with hierarchical superstructures having superhydrophobicity and trapping abilities for the capture of persistent water contaminants such as oils and microplastics. We expect that this strategy could serve as inspiration for the construction of more intricate multiscale structures that could greatly expand the library of HOF materials.

A Simple and Sequential Strategy for the Introduction of Complexity and Hierarchy in Hydrogen‐Bonded Organic Framework (HOF) Crystals for Environmental Applications

AbstractHydrogen‐bonded organic frameworks (HOFs) are a new class of crystalline porous organic molecular materials (POMMs) with great potential for a diverse range of applications. HOFs face common challenges to POMMs, and in general to purely organic crystals, that is, the difficulty of integrating complexity in crystals. Herein, we propose a simple and sequential strategy for the formation of HOFs with hierarchical superstructures. The strategy is based on controlling the assembly conditions, avoiding the use of any surface functionalization or template, which allows to obtain hierarchical crystalline porous superstructures in an easy manner. As proof of concept, we obtained the first example of core–shell (HOF‐on‐HOF) crystals and HOFs with hierarchical superstructures having superhydrophobicity and trapping abilities for the capture of persistent water contaminants such as oils and microplastics. We expect that this strategy could serve as inspiration for the construction of more intricate multiscale structures that could greatly expand the library of HOF materials.

Coassembly of Complementary Polyhedral Metal-Organic Framework Particles into Binary Ordered Superstructures.

Here we report the formation of a 3D NaCl-type binary porous superstructure via coassembly of two colloidal polyhedral metal-organic framework (MOF) particles having complementary sizes, shapes, and charges. We employed a polymeric-attenuated Coulombic self-assembly approach, which also facilitated the coassembly of these MOF particles with spherical polystyrene particles to form 2D binary superstructures. Our results pave the way for using MOFs to create sophisticated superstructures comprising particles of various sizes, shapes, porosities, and chemical compositions.

Computationally guided synthesis of a hierarchical [4[2+3]+6] porous organic ‘cage of cages’

Here we report a two-step, hierarchical synthesis that assembles a trigonal prismatic organic cage into a more symmetric, higher-order tetrahedral cage, or ‘cage of cages’. Both the preformed [2+3] trigonal prismatic cage building blocks and the resultant tetrahedral [4[2+3]+6]cage molecule are constructed using ether bridges. This strategy affords the [4[2+3]+6]cage molecule excellent hydrolytic stability that is not a feature of more common dynamic cage linkers, such as imines. Despite its relatively high molar mass (3,001 g mol−1), [4[2+3]+6]cage exhibits good solubility and crystallizes into a porous superstructure with a surface area of 1,056 m2 g−1. By contrast, the [2+3] building block is not porous. The [4[2+3]+6]cage molecule shows high CO2 and SF6 uptakes due to its polar skeleton. The preference for the [4[2+3]+6]cage molecule over other cage products can be predicted by computational modelling, as can its porous crystal packing, suggesting a broader design strategy for the hierarchical assembly of organic cages with synthetically engineered functions.

A Novel Homoconjugated Propellane Triimide: Synthesis, Structural Analyses, and Gas Separation.

Rigid three-dimensional (3D) polycyclic propellanes have garnered interest due to their unique conformational spaces, which display great potential use in selectivity, separation and as models to study through-space electronic interactions. Herein we report the synthesis of a novel rigid propellane, trinaphtho[3.3.3]propellane triimide, which comprises three imide groups embedded on a trinaphtho[3.3.3]propellane. This propellane triimide exhibits large bathochromic shift, amplified molar absorptivity, enhanced fluorescence, and lower reduction potential when compared to the subunits. Computational and experimental studies reveal that the effective through-space π-orbitals interacting (homoconjugation) occurs between the subunits. Single-crystal XRD analysis reveals that the propellane triimide has a highly quasi-D3h symmetric skeleton and readily crystallizes into different superstructures by changing alkyl chains at the imide positions. In particular, the porous 3D superstructure with S-shaped channels is promising for taking up ethane (C2H6) with very good selectivity over ethylene (C2H4), which can purify C2H4 from C2H6/C2H4 in a single separation step. This work showcases a new class of rare 3D polycyclic propellane with intriguing electronic and supramolecular properties.

A Novel Homoconjugated Propellane Triimide: Synthesis, Structural Analyses, and Gas Separation

AbstractRigid three‐dimensional (3D) polycyclic propellanes have garnered interest due to their unique conformational spaces, which display great potential use in selectivity, separation and as models to study through‐space electronic interactions. Herein we report the synthesis of a novel rigid propellane, trinaphtho[3.3.3]propellane triimide, which comprises three imide groups embedded on a trinaphtho[3.3.3]propellane. This propellane triimide exhibits large bathochromic shift, amplified molar absorptivity, enhanced fluorescence, and lower reduction potential when compared to the subunits. Computational and experimental studies reveal that the effective through‐space π‐orbitals interacting (homoconjugation) occurs between the subunits. Single‐crystal XRD analysis reveals that the propellane triimide has a highly quasi‐D3h symmetric skeleton and readily crystallizes into different superstructures by changing alkyl chains at the imide positions. In particular, the porous 3D superstructure with S‐shaped channels is promising for taking up ethane (C2H6) with very good selectivity over ethylene (C2H4), which can purify C2H4 from C2H6/C2H4 in a single separation step. This work showcases a new class of rare 3D polycyclic propellane with intriguing electronic and supramolecular properties.

DNA-Directed Assembly of Hierarchical MOF-Cellulose Nanofiber Microbioreactors with "Branch-Fruit" Structures.

Assembling metal-organic frameworks (MOFs) into ordered multidimensional porous superstructures promises the encapsulation of enzymes for heterogeneous biocatalysts. However, the full potential of this approach has been limited by the poor stability of enzymes and the uncontrolled assembly of MOF nanoparticles onto suitable supports. In this study, a novel and exceptionally robust Ni-imidazole-based MOF was synthesized in water at room temperature, enabling in situ enzyme encapsulation. Based on this MOF platform, we developed a DNA-directed assembly strategy to achieve the uniform placement of MOF nanoparticles onto bacterial cellulose nanofibers, resulting in a distinctive "branch-fruit" structure. The resulting hybrid materials demonstrated remarkable versatility across various catalytic systems, accommodating natural enzymes, nanoenzymes, and multienzyme cascades, thus showcasing enormous potential as universal microbioreactors. Furthermore, the hierarchical composites facilitated rapid diffusion of the bulky substrate while maintaining the enzyme stability, with ∼3.5-fold higher relative activity compared to the traditional enzyme@MOF immobilized in bacterial cellulose nanofibers.

Rapid production of 3D porous superstructures for energy storage and infrared stealth

Rapid production of 3D porous superstructures for energy storage and infrared stealth

Design of B/N Co-doped micro/meso porous carbon electrodes from CNF/BNNS/ZIF-8 nanocomposites for advanced supercapacitors

Boron (B) and nitrogen (N) co-doped 3D hierarchical micro/meso porous carbon (BNPC) were successfully fabricated from cellulose nanofiber (CNF)/ boron nitride nanosheets (BNNS)/ zinc-methylimidazolate framework-8 (ZIF-8) nanocomposites prepared by 2D BNNS, ZIF-8 nanoparticles, and wheat straw based CNFs. Herein, CNF/ZIF-8 acts as versatile skeleton and imparts partial N dopant into porous carbon structure, while the introduced BNNS can help strengthen the hierarchical porous superstructure and endow abundant B/N co-dopants within BNPC matrix. The obtained BNPC electrode possesses a high specific surface area of 505.4 m2/g, high B/N co-doping content, and desirable hydrophilicity. Supercapacitors assembled with BNPC-2 (B/N co-doped porous carbon with a CNF/BNNS mass ratio of 1꞉2) electrodes exhibited exceptional electrochemical performance, demonstrating high capacitance stability even after 5 000 charge-discharge cycles. The devices exhibited outstanding energy density and power density, as well as the highest specific capacitance of 433.4 F/g at 1.0 A/g, when compared with other similar reports. This study proposes a facile and sustainable strategy for efficiently fabrication of rich B/N co-doped hierarchical micro/meso porous carbon electrodes from agricultural waste biomass for advanced supercapacitor performance.

Engineered In-Situ-Forming Biomimetic Hydrogel with Self-Regulated Immunostimulatory Capacity Promotes Postoperative Tumor Treatment

Post-resection tumors with microscopic foci and immunosuppressive microenvironments have high risk of recurrence and metastasis but respond poorly to various therapies. Herein, we propose a biomimetic hydrogel as a biocompatible, biodegradable and bioadhesive postoperative dressing that could be formed in situ by NaIO4-initiated thiourea-catechol crosslinking after syringe-injection into the resection cavity. The thiourea or catechol-bearing hyaluronic acid (HA) precursors are also separately engineered with phenylboronic acid and β-cyclodextrin (β-CD) groups, potentiating the reversible immobilization of (1S, 3R) RAS-selective lethal 3 (RSL3) and glycosylated granulocyte macrophage-colony stimulating factor (GM-CSF) without invasive chemical reactions. Meanwhile, the interconnected porous superstructure of the hydrogels allows the incorporation and self-regulated delivery of PD-L1 antibody (aPD-L1). RSL3-induced immunogenic ferroptosis and GM-CSF could cooperatively trigger robust adaptive tumor-specific immune responses, while aPD-L1 further alleviates the accumulated immunoresistance of tumor cells due to interferon γ-mediated PD-L1 upregulation, thus stimulating potent local and whole-body antitumor immunity to prevent postoperative tumor recurrence and metastasis. The biomimetic hydrogel may serve as a promising solution for the postoperative treatment of solid tumors.

Hierarchically ordered porous superstructure embedded with readily accessible atomic pair sites for enhanced CO2 electroreduction

Herein, a hierarchically ordered porous superstructure of N-doped carbon embedded with readily accessible Fe-Ni diatomic sites (FeNi DASs/HOPSNC) has been synthesized for highly efficient CO2 electroreduction. By integrating additional secondary mesopores into the ordered macroporous skeleton, this distinctive superstructure exhibits greatly enhanced accessibility and mass transfer. Benefiting from the unique structure merits including the synergistic effect in Fe-Ni atomic pair sites and the multi-level porosity, such diatomic site catalyst affords an outstanding electrocatalytic performance with excellent activity and selectivity for CO2-to-CO conversion and remarkable stability. Furthermore, systematic characterizations and density functional theory calculations unveiled that the electronic interaction within the diatomic pairs leads to the optimized electronic state and decreased reaction energy barrier for generating COOH* intermediate and weakening the binding strength of CO*, thereby improving the intrinsic catalytic activity and selectivity. This work may inspire further development of high-performance diatomic site catalysts for CO2 electroreduction and other electrosynthesis.

Self-assembly of colloidal metal-organic framework (MOF) particles.

Self-assembly of colloidal particles into ordered superstructures enables the development of novel advanced materials for diverse applications such as photonics, electronics, sensing, energy conversion, energy storage, diagnosis, drug or gene delivery, and catalysis. Recently, polyhedral metal-organic framework (MOF) particles have been proposed as promising colloidal particles to form ordered superstructures, based on their colloidal stability, size-tunability, rich polyhedral shapes, porosity and multifunctionality. In this review, we present a comprehensive overview of strategies for the self-assembly of colloidal MOF particles into ordered superstructures of different dimensionalities, highlighting some of their properties and applications, and sharing thoughts on the self-assembly of MOF particles.

Rational construction of Ag@MIL-88B(V)-derived hierarchical porous Ag-V2O5 heterostructures with enhanced diffusion kinetics and cycling stability for aqueous zinc-ion batteries

With the advantages of the multiple oxidation states and highly open crystal structures, vanadium-based composites have been considered as the promising cathode materials for aqueous zinc-ion batteries (ZIBs). However, the inherent inferior electrical conductivity, low specific surface area, and sluggish Zn2+ diffusion kinetics of the traditional vanadium-based oxides have greatly impeded their development. Herein, a novel hierarchical porous spindle-shaped Ag-V2O5 with unique heterostructures was rationally designed via a simple MOF-assisted synthetic method and applied as stable cathode for aqueous ZIBs. The high specific surface area and hierarchically porous superstructures endowed Ag-V2O5 with sufficient electrochemical active sites and shortened the diffusion pathways of Zn2+, which was beneficial to accelerate the reversible transport of Zn2+ and deliver a high specific capacity (426 mA h g−1 at 0.1 A g−1 and 96.5% capacity retention after 100 cycles). Meanwhile, the self-built-in electric fields at the heterointerface of Ag-V2O5 electrode could strengthen the synergistic coupling interaction between Ag and V2O5, which can effectively enhance the electric conductivity and maintain the structural integrity, resulting in superb rate capability (326.1 mA h g−1 at 5.0 A g−1) and remarkable cycling stability (89.7% capacity retention after 2000 cycles at 5.0 A g−1). Moreover, the reversible Zn2+ storage mechanism was further investigated and elucidated by kinetics analysis and DFT calculations.

Biomass derived carbonaceous materials with tailored superstructures designed for advanced supercapacitor electrodes

Supercapacitors (SC), as one of the most competitive energy storage devices, are receiving great attention in R&D community. Carbonaceous materials for supercapacitor electrodes with high performance possess many attractive advantages, such as large specific surface area (SSA), hierarchical porous superstructures and excellent conductivity. Herein, biomass based materials are often utilized as versatile precursors for activated carbon production due to their inherent merits, including low cost, abundance, renewability, high carbon content, environmental friendliness, genetically unique nature structure. As known, the capacitance performance of biomass based carbon-assembled supercapacitors is mainly directly proportional to the exceptional skeleton robustness, high SSA and electroactive site content within carbonaceous framework. In this review, special attentions will be paid to the latest research progress of carbonaceous materials derived from biomass with tailored hierarchical superstructures to highlight their impact on the electrochemical performance of assembled supercapacitor. The objective of this paper is to present a critical review on the most recent publication related to biomass oriented carbonaceous electrodes for outstanding supercapacitor electrodes. Furthermore, the perspective for the progress and development of biomass based carbonaceous electrodes for high performance supercapacitors will also be provided, to underscore the current critical issues and future opportunities. • Carbon derived from biomass with tailored structure for supercapacitors was reviewed. • Methods for activating carbon with improved capacitance were reviewed and discussed. • Biomass based carbon and their key parameters/ characterizations were summarized. • The reasons why biomass derived carbon are suitable for electrodes were demonstrated. • Preparation methods and applications of biomass derived carbon were summarized and prospected.

Hierarchical hollow superstructure cobalt selenide bird nests for high-performance lithium storage

The inferior cycling performance caused by large volume variation is the main problem that restricts the application of cobalt selenides in lithium-ion batteries. Herein, we synthesize raspberry-like Co-ethylene glycol precursor. It is further selenized into the hierarchical hollow superstructure CoSe2/CoSe bird nests that are assembled by the hollow nanosphere units of CoSe2 and CoSe nanocrystalline. CoSe2/CoSe bird nests achieve excellent cycling performance, high reversible capacity and satisfactory rate capability (1361 mAh/g at 1 A/g after 1000 cycles, 579 mAh/g at 2 A/g after 2000 cycles, 315 mAh/g at 5 A/g after 1000 cycles). Electrochemical kinetics analyses and ex-situ material characterization reveal that the surface capacitive behavior controls the electrochemical reaction, and the composite has low reaction impedance, fast and stable Li+ diffusion, and superior structural stability. The superior lithium storage performance is attributed to the unique superstructure bird nest. Large specific surface area, abundant hierarchical pores and the opening mouth result in high electrochemical activity, which induces high reversible capacity. The small hollow nanosphere units, the sufficiently thick hierarchical porous superstructure shell and the large hollow interior bring about the strong synergistic effect to improve cycling performance. The intimately coupling of CoSe2/CoSe nanocrystalline and the hollow nanosphere units guarantees high conductivity. This work has greatly enriched the understanding of structure design of high-performance cobalt selenide anodes.

Ion exchange fabrication of lanthanide functionalized layered double hydroxides microcapsules for rapid and visual detection of anthrax biomarker

Lanthanide ion probes have recently been considered as promising sensing materials due to their high sensitivity and good optical properties. Herein, the 3D hierarchical lanthanide functionalized layered double hydroxides microcapsules were synthesized via a facile ion exchange strategy and further developed as novel fluorescent probes for detecting trace amounts of the anthrax biomarker dipicolinicacid (DPA). Benefiting from the 3D porous superstructure and abundant unsaturated coordination sites of lanthanide ion, the ternary Ni-Fe-Ln-LDHs (Ln = Tb/Eu) not only possess a large reactive contact area to improve the sensitivity of DPA detection, but also demonstrate very fast reaction rate. The design of inexpensive fluorescent test strips can perform the on-site and real-time detection via a smartphone with a color recognition application. More prominently, the sensitivity of the system was evaluated by actual spore samples with the detection limit as low as 3.54 × 104 spores/mL. The 3D lanthanide functionalized LDHs nanoprobe constructed by ion exchange exhibits a new vision for the development of a sensing platform in other research areas.

CMP-on-MOF bimetallic hybrids derived sheet-on-rod heterostructure as bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries

As a simple but effective approach to engineer the simultaneous geometric structure and composition diversity into one nano-material, hybrids have geared great research attention, recently. Here, a N-decorated sheet-on-rod heterostructure with hierarchical porosity, as well as homogeneously dispersed Co5.47N, Co0.7Fe0.3, and Fe/Co-Nx species on the phase interface, was developed via pyrolysis of a CMP-on-MOF bimetal hybrid, to achieve the bifunctional oxygen electrocatalytic activity. Conjugated microporous polymers (CMPs) are an emerging class of multifunctional materials combining the features of conventional conjugated polymers and porous materials, simultaneously. CMP-on-MOF was prepared via the assembly of Co-phthalocyanine-CMP (Co-CMP) on the surface of Fe-MIL-88B (Fe-MOF) through a solid-phase synthesis method. The optimized catalyst (PM-900), namely the product of hybrid pyrolysis, is obtained by finely regulating the composition of hybrid (mCMP to mMOF of 1:1) and pyrolysis temperature (900 °C) on the hybrid, simultaneously. The abundant Co5.47N, Co0.7Fe0.3, and atomically dispersed Fe/Co-Nx species are highly catalytically active, and the hierarchical porous structure provides easily accessible pathway for active sites, and the sheet-on-rod structure ensures a high electrical conductivity which is conducive for the catalysis. As a result, the optimum electrocatalyst, denoted as PM-900, presents a superb bifunctional electrocatalytic activity for both the oxygen reduction (ORR) and oxygen evolution reaction (OER) under alkaline conditions. Additionally, a home-made Zn–air battery (ZAB) comprising PM-900 catalyst presents prominent charge-discharge property even outperforms the mixture of Pt/C (20 wt%) and IrO2. The hybrid strategy paves a new avenue for the rational design and synthesis of advanced bifunctional catalysts with intricate and unprecedented porous superstructures for reversible energy storage and conversion applications.

Zinc cobaltite micro-stars with a zinc oxide nano-stubs overlayer based supercapacitor colors a polyaniline//tungsten oxide electrochromic device

Zinc cobaltite(ZnCo2O4) micro-star shaped porous superstructure, on coating with zinc oxide(ZnO) nano-stubs, and coupling with porous flaky activated carbon(AC) from green tea, yielded asymmetric supercapacitor(ASC) with greatly enhanced performance parameters: specific capacitance(SC) of 557 F g−1, energy and power density(E and P) maxima of 173 Wh kg−1 and ∼3 kW kg−1, compared to reported ASCs of carbon/ZnCo2O4 composites and pure ZnCo2O4 or ZnO. Sub-stoichiometry in ZnO overlayer endows it with good electrical conductivity (14.6 mS cm−1), enhancing overall electron circulation in composite and due to direct contact between two oxides, with different morphologies and sufficient porosity, electrolyte penetration is deep, and ample ion-accommodation sites prevail in ZnO@ZnCo2O4 composite, which translate into increased SC, E, P, rate-response and cycle life. Usefulness of high-performance AC//ZnO@ZnCo2O4 ASC is ratified by connecting it in its fully charged state to electrochromic device (ECD) of polyaniline and tungsten oxide, and large integrated transmission modulation of 45.8% was rendered in ECD over bulk of visible region (480–800 nm). This demonstration of self-powering ECD proved efficacy of these devices for futuristic applications, where, dual functions of energy storage and saving can be tapped, by using such low cost, highly efficient devices, that can not only work independently, but can also work in tandem.

Garland, Flower, and Petals via a Hierarchical Self-Assembly of Ursane-Type Triterpenoid Uvaol.

Uvaol, a 6-6-6-6-6 pentacyclic dihydroxy ursane-type triterpenoid, is isolable from different parts of plants Plumeria rubra, Olea europaea, Nerium oleander, Lavandula pedunculta, and Malus domestica. It is also obtained by a one-step reduction of naturally occurring triterpenoid ursolic acid. Herein, we report the first self-assembly properties of uvaol in different neat organic liquids and aqueous organic binary liquid mixtures. Spontaneous self-assembly of uvaol in different neat liquids and binary liquid mixtures yielded garland, flower, and petal-like porous superstructures of nano- to micrometer dimensions. Utilization of self-assemblies has been demonstrated in generation of anticancer drug conjugates and the removal of carcinogenic and toxic chemicals.