3D Porous Architecture Research Articles

Multielectrode electrochemical cell for in situ structural characterization of amorphous thin-film catalysts using high-energy X-ray scattering

A multielectrode-based electrochemical cell allows the structural characterization of an amorphous thin-film water oxidation catalyst under various electrochemical potentials using high-energy X-ray scattering and atomic pair distribution function (PDF) techniques. A multielectrode with five electrodes provides a sufficiently low background signal to enable high-energy X-ray scattering (HEXS) measurements and amplifies the extremely low HEXS signals from samples for high-resolution PDF analysis of in situ data from thin-film catalysts. Glassy carbon (GC) creates a relatively low intensity HEXS pattern and is used as a working electrode. Instead of a three-dimensional (3D) porous electrode architecture, the flat geometry of the electrode enables various deposition techniques to be used for the preparation of a highly conductive metal oxide layer. PDF analysis demonstrates high spatial resolution for a 230 nm thick amorphous iridium oxide film deposited on two roughened 60 µm thick GC electrodes. The PDF analysis resolves the domain size and distinguishes changes in fine structure which are directly correlated with the structure and function of the catalysts. The results bring the opportunity to analyze the structure of nanometre-scale amorphous thin-film catalysts in an electrolyte-compatible and compact 3D-printed electrochemical cell in a three-electrode configuration.

Supramolecular Enhancement of Electrochemical Nitrate Reduction Catalyzed by Cobalt Porphyrin Organic Cages for Ammonia Electrosynthesis in Water.

The electrochemical nitrate (NO3 - ) reduction reaction (NO3 RR) to ammonia (NH3 ) represents a sustainable approach for denitrification to balance global nitrogen cycles and an alternative to traditional thermal Haber-Bosch processes. Here, we present a supramolecular strategy for promoting NH3 production in water from NO3 RR by integrating two-dimensional (2D) molecular cobalt porphyrin (CoTPP) units into a three-dimensional (3D) porous organic cage architecture. The porphyrin box CoPB-C8 enhances electrochemical active site exposure, facilitates substrate-catalyst interactions, and improves catalyst stability, leading to turnover numbers and frequencies for NH3 production exceeding 200,000 and 56 s-1 , respectively. These values represent a 15-fold increase in NO3 RR activity and 200-mV improvement in overpotential for the 3D CoPB-C8 box structure compared to its 2D CoTPP counterpart. Synthetic tuning of peripheral alkyl substituents highlights the importance of supramolecular porosity and cavity size on electrochemical NO3 RR activity. These findings establish the incorporation of 2D molecular units into 3D confined space microenvironments as an effective supramolecular design strategy for enhancing electrocatalysis.

Supramolecular Enhancement of Electrochemical Nitrate Reduction Catalyzed by Cobalt Porphyrin Organic Cages for Ammonia Electrosynthesis in Water**

AbstractThe electrochemical nitrate (NO3−) reduction reaction (NO3RR) to ammonia (NH3) represents a sustainable approach for denitrification to balance global nitrogen cycles and an alternative to traditional thermal Haber‐Bosch processes. Here, we present a supramolecular strategy for promoting NH3 production in water from NO3RR by integrating two‐dimensional (2D) molecular cobalt porphyrin (CoTPP) units into a three‐dimensional (3D) porous organic cage architecture. The porphyrin box CoPB‐C8 enhances electrochemical active site exposure, facilitates substrate–catalyst interactions, and improves catalyst stability, leading to turnover numbers and frequencies for NH3 production exceeding 200,000 and 56 s−1, respectively. These values represent a 15‐fold increase in NO3RR activity and 200‐mV improvement in overpotential for the 3D CoPB‐C8 box structure compared to its 2D CoTPP counterpart. Synthetic tuning of peripheral alkyl substituents highlights the importance of supramolecular porosity and cavity size on electrochemical NO3RR activity. These findings establish the incorporation of 2D molecular units into 3D confined space microenvironments as an effective supramolecular design strategy for enhancing electrocatalysis.

A Generic “Engraving in Aprotic Medium” Strategy toward Stabilized Zn Anodes

AbstractZn foil pretreatment is a direct route to alleviating Zn anode instability and maintaining high energy performance in Zn metal batteries. Unfortunately, prevailing methods for achieving an ideal Zn surface texture do not enable durable operation under a large depth of discharge, thus impairing the Zn utilization ratio. Zn etching is a more feasible way to control the surface texture, but this approach remains relatively unexplored. In this study, a general strategy is reported for Zn foil engraving in aprotic media to realize efficient anode pretreatment in terms of stability. These tests are performed using high‐valence metal ions (especially Mo5+) in an aprotic environment as the key etchant to render a homogenously‐distributed, 3D porous architecture on the Zn foil surface. Comprehensive experimental results and theoretical simulations revealed enhanced Zn nucleation and growth. This specially designed electrode exhibited a long lifespan with a large depth of discharge of 88% in symmetric cells. When assembled with a ZnxV2O5 cathode, the constructed cell demonstrated nearly full capacity retention even under stringent conditions (e.g., an N/P capacity ratio of 5.5). This study demonstrates the potential of a Zn etching pretreatment to address the prototypical instability issues of Zn anodes.

Synthesis of tea dregs-derived 3D interconnected honeycomb-like porous activated carbon for supercapacitor applications

ABSTRACT Biomass-derived porous activated carbon and their applications as supercapacitor (SC) electrode materials have gained immense research interest owing to their abundance, inexpensive, recyclable, etc. Herein, we report the synthesis of tea dregs-derived 3D interconnected honeycomb-like porous activated carbon (HCAC) via a simple, effective, and inexpensive method for SC applications. Tea dregs waste was activated using NaOH activation with different mass ratios of 1:3, 1:4, and 1:5 under a N2 atmosphere at 800°C for 3.5 h. The scanning electron microscope, energy dispersive X-ray (EDX) spectroscopy, adsorption/desorption isotherm of N2, X-ray diffraction (XRD), FT-IR, and cyclic voltammetry methods were employed to analyze surface morphology, elemental compositions, specific surface area, crystallographic feature, surface functional groups, and electrochemical behavior, respectively. The as-obtained HCAC-3 has a 3D interconnected honeycomb-like porous architecture with high carbon and oxygen contents, achieved the specific surface area of 624 m2/g, amorphous carbon structure, and containing oxygen functional group. The symmetrical SC devices have an optimum specific capacitance of 100 F/g with an optimum energy density of 13.89 Wh/kg at a power density of 50.05 W/kg. This study could provide a good reference for the synthesis of biomass-derived 3D interconnected HCAC and its applications in energy storage devices systems, catalysts, and adsorbents.

Super expanded freestanding 3D graphene foam as a versatile platform for CO2 capture and hydrogenation

A robust fabrication process has been developed to produce super-expanded freestanding 3D reduced graphene oxide foams (SE-rGO) with an outstanding porous architecture and stable geometry for effective capture (from the atmosphere) and the conversion of CO2 into fuel. The 3D SE-rGO foam was prepared using salicylic acid-induced exfoliation of graphene layers based on a template-assisted process. The foam was then coated with a thin layer of polydopamine (pDA) to enhance its physical and functional properties. The morphology and structural integrity of the foam were examined using SEM, XRD, XPS, and TGA. Owing to its unique 3D porous architecture and large specific surface area (767 m2/g, SSA), the foam displayed excellent multifunctional attributes, namely high CO2 adsorption capacity (4.17 mmol/g) and catalytic support for effective CO2 hydrogenation to formate. The key catalytic activity was made possible by coating the foam with palladium nanoparticles. The coated foam showed outstanding hydrogenation of CO2 to formate with a maximum yield of 24.3% at 120 °C. Given its potential, this graphene foam can be a promising and versatile material for both CO2 capture and CO2 hydrogenation.

Matrilin-2 within a three-dimensional lysine-modified chitosan porous scaffold enhances Schwann cell migration and axonal outgrowth for peripheral nerve regeneration.

Background: Matrilin-2 is a key extracellular matrix protein involved in peripheral nerve regeneration. We sought to develop a biomimetic scaffold to enhance peripheral nerve regeneration by incorporating matrilin-2 within a chitosan-derived porous scaffold. We hypothesized that the use of such a novel biomaterial delivers microenvironmental cues to facilitate Schwann cell (SC) migration and enhance axonal outgrowth during peripheral nerve regeneration. Materials and Methods: The effect of matrilin-2 on SC migration was evaluated with agarose drop migration assay on matrilin-2 coated dishes. SC adhesion was determined with SCs cultured atop tissue culture dishes coated with matrilin-2. Various formulations of chitosan vs matrilin-2 in scaffold constructs were examined with scanning electron microscopy. The effect of the matrilin-2/chitosan scaffold on SC migration in the collagen conduits was determined by capillary migration assays. Neuronal adhesion and axonal outgrowth were evaluated with three-dimensional (3D) organotypic assay of dorsal root ganglions (DRG). DRG axonal outgrowth within the scaffolds was determined by immunofluorescence staining of neurofilaments. Results: Matrilin-2 induced SC migration and enhanced its adhesion. A formulation of 2% chitosan with matrilin-2 demonstrated an optimal 3D porous architecture for SC interaction. Matrilin-2/chitosan scaffold enabled SCs to migrate against gravity within conduits. Chemical modification of chitosan with lysine (K-chitosan) further improved DRG adhesion and axonal outgrowth than the matrilin-2/chitosan scaffold without lysine modification. Conclusion: We developed a matrilin-2/K-chitosan scaffold to mimic extracellular matrix cues and provide a porous matrix to enhance peripheral nerve regeneration. Taking advantage of matrilin-2's capability to stimulate SC migration and adhesion, we formulated a porous matrilin-2/chitosan scaffold to support axongal outgrowth. Chemical modification of chitosan with lysine further improved matrilin-2 bioactivity in the 3D scaffold. The 3D porous matrilin-2/K-chitosan scaffolds have high potential for enhancing nerve repair by stimulating SC migration, neuronal adhesion, and axonal outgrowth.

Polylevolysine and Fibronectin-Loaded Nano-Hydroxyapatite/PGLA/Dextran-Based Scaffolds for Improving Bone Regeneration: A Histomorphometric in Animal Study.

The regeneration of large bone defects is still demanding, requiring biocompatible scaffolds, with osteoconductive and osteoinductive properties. This study aimed to assess the pre-clinical efficacy of a nano-hydroxyapatite (nano-HA)/PGLA/dextran-based scaffold loaded with Polylevolysine (PLL) and fibronectin (FN), intended for bone regeneration of a critical-size tibial defect, using an ovine model. After physicochemical characterization, the scaffolds were implanted in vivo, producing two monocortical defects on both tibiae of ten adult sheep, randomly divided into two groups to be euthanized at three and six months after surgery. The proximal left and right defects were filled, respectively, with the test scaffold (nano-HA/PGLA/dextran-based scaffold loaded with PLL and FN) and the control scaffold (nano-HA/PGLA/dextran-based scaffold not loaded with PLL and FN); the distal defects were considered negative control sites, not receiving any scaffold. Histological and histomorphometric analyses were performed to quantify the bone ingrowth and residual material 3 and 6 months after surgery. In both scaffolds, the morphological analyses, at the SEM, revealed the presence of submicrometric crystals on the surfaces and within the scaffolds, while optical microscopy showed a macroscopic 3D porous architecture. XRD confirmed the presence of nano-HA with a high level of crystallinity degree. At the histological and histomorphometric evaluation, new bone formation and residual biomaterial were detectable inside the defects 3 months after intervention, without differences between the scaffolds. At 6 months, the regenerated bone was significantly higher in the defects filled with the test scaffold (loaded with PLL and FN) than in those filled with the control scaffold, while the residual material was higher in correspondence to the control scaffold. Nano-HA/PGLA/dextran-based scaffolds loaded with PLL and FN appear promising in promoting bone regeneration in critical-size defects, showing balanced regenerative and resorbable properties to support new bone deposition.

Nickel-coated 3D-printed titanium electrodes for electrochemical flow reactors

ABSTRACT Electrocatalyst-coated metallic electrodes for electrochemical flow reactors have many applications in electrosynthesis, environmental remediation and energy conversion. This work presents novel nickel-coated titanium-alloy electrodes produced by means of direct metal laser sintering and constant current electrodeposition in an additive-free Wood’s nickel strike then a Watts nickel bath. Several 3D porous architectures were created in Ti-6Al-4 V alloy and coated, their digital design being the subject of previous work. Nickel coatings were macroscopically uniform and adherent with a thickness up to 5.8 µm, depending on the surface area of the electrodes. The morphology of nickel was cauliflower-like, with crystallisation growth occurring as spherical grains, as typically found for deposits from pH buffered Watts baths. Some degree of coating porosity was observed at electrodes of large surface area, indicating the need for longer deposition times. The results open the path for further optimisation of electrodeposition parameters and the development of bath additives to tailor deposit properties.

Influence of the catalyst layer thickness on the determination of the OER activity of Fe3O4@CoFe2O4 core-shell nanoparticles

Transition metal oxides-based catalytic layers often present a complex 3D porous architecture affecting the evaluation of their intrinsic electrocatalytic activity. In this work the oxygen evolution reaction activity of core-shell Fe3O4@CoFe2O4 nanoparticles combining a conductive magnetite core and a catalytically active cobalt ferrite shell was studied at different loading and thickness of the catalytic layer. It was observed that their apparent activity is decreasing and that the Tafel slopes are becoming convex when the loading increases. The activity decay could be attributed to the significant resistance to charge transport in the thick porous catalyst layer. This resistance could be estimated by fitting the electrochemical impedance spectra using the transmission line model. The influence of the layer thickness on the experimental current-potential curves and on their Tafel slopes could be simulated using a simple model based on the Telegrapher's equations. It is concluded that in order to measure accurately the activity and Tafel slopes of an electrocatalyst, thin layers must be used, notably for catalyst layers that are not highly conductive.

Tailoring NH4+ storage by regulating oxygen defect in ammonium vanadate

Defect engineering is an effective strategy for modifying the energy storage materials to improve their electrochemical performance. However, the impact of oxygen defect and its content on the electrochemical performances in the burgeoning aqueous NH4+ storage field remains explored. Therefore, for the first time in this work, an oxygen-defective ammonium vanadate [(NH4)2V10O25·8H2O, denoted as Od-NHVO] with a novel 3D porous flower-like architecture was achieved via the reduction of thiourea in a mild reaction condition, which is a facile method that can realize the intention to regulate the oxygen defect content, with the capability of mass-production. The as-prepared OdM-NHVO with moderate oxygen defect content can deliver a stable specific capacitance output (505 F g−1, 252 mAh g−1 at 0.5 A g−1 with ∼80% capacitance retention after 10,000 cycles), which benefits from extra active sites, unimpeded NH4+-migration path and relatively high structure integrity. In contrast, low oxygen defect content will lead to the torpid electrochemical reaction kinetics while too high content of it will reduce the charge-storage capability and induce structural disintegration. The superior NH4+-storage behavior is achieved with the reversible intercalation/de-intercalation process of NH4+ accompanied by forming/breaking of hydrogen bond. As expected, the assembled flexible OdM-NHVO//PTCDI quasi-solid-state hybrid supercapacitor (FQSS HSC) also exhibits high areal capacitance, energy density and reliable flexibility. This work provides a new avenue for developing materials with oxygen-deficient structure for application in various aqueous non-metal cation storage systems.

A Co(II)–organic framework and peroxidase mimetic Hemin@metal–organic framework and its application in the colorimetric analysis of glucose

A Co(II)‐organic framework (Co‐MOF), [Co3(3,5‐bimpy)2(5‐cpia)2(H2O)2], was constructed via the hydrothermal reaction of 3,5‐bis(1‐imidazoly)pyridine (3,5‐bimpy) and 5‐(2′‐carboxylphenoxy)isophthalic acid (5‐H3cpia). The Co‐MOF possessed a three‐dimensional (3D) porous architecture with the porosity of 22.4% per unit volume. The Co‐MOF@Hemin composite was further constructed via the encapsulation of Hemin into the Co‐MOF material. The constructed Co‐MOF@Hemin exhibited satisfactory peroxidase‐like activity through catalytic oxidation of the colorless peroxidase substrate 3,3,5,5‐tetramethylbenzidine (TMB) to a blue‐colored oxTMB in the presence of H2O2. Hence, the detection of H2O2 was achieved with a wide linear range from 0.005 to 0.5 mM (R2 = 0.992) and a low detection limit of 1.26 μM. More importantly, the peroxidase‐like Co‐MOF@Hemin was suitable for the sensitive and selective detection of glucose under the presence of glucose oxidase (GOx), which reduced O2 to H2O2. This analytical procedure for the detection of glucose had a linear range from 0.3 to 3 mM (R2 = 0.997), with a detection limit of 49 μM. The experimental results display the broad application prospects of the enzyme‐based MOFs in green and selective targets analyses.

Constructing Mechanical Shuttles in a Three-dimensional (3D)Porous Architecture for Selective Transportof Lithium Ions.

Lithium(Li)extraction from brinesis a major barrier to the sustainable development of batteries and alloys;however, current separation technology suffers from a trade-off between ion selectivity andpermeability. Herein, a crown ether mechanically interlocked 3D porous organic framework (Crown-POF) was prepared as the porous filler of thin-film nanocomposite membranes. Crown-POF with penta-coordinated(four O crown atoms and one N tert-amine atom)adsorptionsites enables a special recognition for Li+ion. Moreover, thefour N tert-amine atoms on each POF branch facilitate the flipping motion of Li+ion along the skeletal thread, while retaining the specified binding pattern. Accordingly, the crown ether interlocked POF network displays an ultrafast ion transfer rate, over 10 times that of the conventional porous materials.Notably, the nanocomposite membrane gives high speed and selectivity for Li+ion transport as compared with other porous solid-based mixed-matrix membranes.

Constructing Mechanical Shuttles in a Three‐dimensional (3D) Porous Architecture for Selective Transport of Lithium Ions

AbstractLithium (Li) extraction from brines is a major barrier to the sustainable development of batteries and alloys; however, current separation technology suffers from a trade‐off between ion selectivity and permeability. Herein, a crown ether mechanically interlocked 3D porous organic framework (Crown‐POF) was prepared as the porous filler of thin‐film nanocomposite membranes. Crown‐POF with penta‐coordinated (four Ocrown atoms and one Ntert‐amine atom) adsorption sites enables a special recognition for Li+ ion. Moreover, the four Ntert‐amine atoms on each POF branch facilitate the flipping motion of Li+ ion along the skeletal thread, while retaining the specified binding pattern. Accordingly, the crown ether interlocked POF network displays an ultrafast ion transfer rate, over 10 times that of the conventional porous materials. Notably, the nanocomposite membrane gives high speed and selectivity for Li+ ion transport as compared with other porous solid‐based mixed‐matrix membranes.

Tuning pyridinic-N and graphitic-N doping with 4,4′-bipyridine in honeycomb-like porous carbon and distinct electrochemical roles in aqueous and ionic liquid gel electrolytes for symmetric supercapacitors

Doping engineering in nanostructured carbon materials is an effective approach to modify heteroatom species and surface electronic structures. Herein, an advanced electrode material based on a honeycomb-like porous carbon matrix with tunable N-doped configurations is prepared via 4,4′-bipyridine (4,4′-bpy)-assisted pyrolysis of SiO2@ZIF-8 templates and subsequent etching treatment. Interestingly, the amounts of pyridinic-N and graphitic-N can be controlled by rationally varying the content of 4,4′-bpy which acts as the N source in the pyrolysis process. Both experimental results and density functional theory calculations have revealed that synergistically with 3D interconnected porous architecture, pyridinic-N and graphitic-N have different effects on the electrochemical performances in aqueous and ionic liquid gel electrolytes for symmetric supercapacitors. Highly exposed pyridinic-N endows the carbon electrode with a strengthened pseudocapacitance contribution manifested as a high specific capacitance of 436.1 F g−1 and exceptional stability of almost 100% capacitance retention after 5000 cycles at 10 A g−1 in the KOH/polyvinyl alcohol (PVA) electrolyte. By contrast, graphitic-N is propitious for reinforced electrical double-layer capacitance contribution, reflected by a maximum energy density of 125.4 Wh kg−1 in the 1-ethyl-3-methylimidazolium tetrafluoroborate/poly(vinylidene fluoride-co-hexafluoropropylene) (EMIMBF4/PVDF-HFP) electrolyte. This work offers an in-depth insight into the understanding of the energy storage mechanism of N-rich carbon electrodes in different electrolyte media.

Techno-economically feasible beverage can as superior anode in rechargeable Al-air batteries

Porous Fe nitrogen-doped carbon (Fe-NC) with a polyhedron structure, derived from zeolitic imidazolate framework 8 (ZIF8), was synthesized as an efficient electrocatalyst in Al-air batteries, complemented by a low-cost aluminium anode based on beverage cans. The highly-loaded porous Fe-NC demonstrated efficient catalytic activity towards the oxygen reduction reaction (ORR). This was linked to the good conductivity and the large surface area originating from the observed 3D porous architecture. The RDE test confirmed that the favourable 4-electron pathway for porous Fe-NC was higher than that of the 20 wt% Pt/carbon. Besides the high ORR activity, the Al-air battery demonstrated a maximum power density of 46 mW/cm2 at a current density of 80 mA/cm2. The galvanostatic discharge studies showed a stable voltage discharge plateau (>1.1 V) for current densities between 5 and 20 mA/cm2. The Al-air battery with porous Fe/NC catalyst exhibited a remarkably increased discharge capacity of 1920 mAh/g for the pure Al foil and 1173 mAh/g for the commercial Al can foil at a current density of 20 mA/cm2. The finding indicates that both anode and cathode in this work are techno-economically feasible materials. In addition, the Al-air battery showed large charge-discharge cycles (i.e., 180 cycles, 31 h) at 10 mA/cm2 with a low voltage gap using a beverage can.

Triple-Networked Hybrid Hydrogels Reinforced with Montmorillonite Clay and Graphene Nanoplatelets for Soft and Hard Tissue Regeneration.

Hydrogel is a three-dimensional (3D) soft and highly hydrophilic, polymeric network that can swell in water and imbibe a high amount of water or biological fluids. Hydrogels have been used widely in various biomedical applications. Hydrogel may provide a fluidic tissue-like 3D microenvironment by maintaining the original network for tissue engineering. However, their low mechanical performances limit their broad applicability in various functional tissues. This property causes substantial challenges in designing and preparing strong hydrogel networks. Therefore, we report the triple-networked hybrid hydrogel network with enhanced mechanical properties by incorporating dual-crosslinking and nanofillers (e.g., montmorillonite (MMT), graphene nanoplatelets (GNPs)). In this study, we prepared hybrid hydrogels composed of polyacrylamide, poly (vinyl alcohol), sodium alginate, MMT, and MMT/GNPs through dynamic crosslinking. The freeze-dried hybrid hydrogels showed good 3D porous architecture. The results exhibited a magnificent porous structure, interconnected pore-network surface morphology, enhanced mechanical properties, and cellular activity of hybrid hydrogels.

4D printing of MXene hydrogels for high-efficiency pseudocapacitive energy storage

2D material hydrogels have recently sparked tremendous interest owing to their potential in diverse applications. However, research on the emerging 2D MXene hydrogels is still in its infancy. Herein, we show a universal 4D printing technology for manufacturing MXene hydrogels with customizable geometries, which suits a family of MXenes such as Nb2CTx, Ti3C2Tx, and Mo2Ti2C3Tx. The obtained MXene hydrogels offer 3D porous architectures, large specific surface areas, high electrical conductivities, and satisfying mechanical properties. Consequently, ultrahigh capacitance (3.32 F cm−2 (10 mV s−1) and 233 F g−1 (10 V s−1)) and mass loading/thickness-independent rate capabilities are achieved. The further 4D-printed Ti3C2Tx hydrogel micro-supercapacitors showcase great low-temperature tolerance (down to –20 °C) and deliver high energy and power densities up to 93 μWh cm−2 and 7 mW cm−2, respectively, surpassing most state-of-the-art devices. This work brings new insights into MXene hydrogel manufacturing and expands the range of their potential applications.

Three-dimensional MXenes heterostructures and their applications

Due to their unique surface chemistry, highly adjustable metal components, hydrophilicity, and high carrier concentrations, MXenes are applied in a variety of scenarios. Similar to other two-dimensional (2D) materials, building heterostructures with additional materials to form a 3D porous architecture for MXenes can significantly enhance their functionality and reactivity. Notably, the open structures and well-defined pathways of these 3D structured MXenes can improve ionic and electronic transport, thereby promoting their applications in electrochemical energy storage, sensing, catalysis, and environment. In this review, the recent efforts made on preparing 3D porous MXenes with heterostructures, focusing on MXenes/C, MXenes/inorganics, and MXenes/polymers were summarized. The discussion covers aspects ranging from the design to synthesis of 3D porous MXenes, and their applications in photocatalysis, environmental monitoring and electrochemical energy storage. This review is concluded by presenting the prospects and insights on exploring the relationships between the porosity formation mechanisms, properties and applications of the 3D porous MXenes heterostructures. This review can provide meaningful guidance for the design, fabrication and application of 3D porous MXenes in high-performance materials and devices.

Cotton-derived 3D carbon fiber aerogel to in situ support Bi2O3 nanoparticles as a separation-free photocatalyst for antibiotic removal

Because of abundant oxygen-based groups, natural cotton is adopted as the precursor to in situ fabricate a three-dimensional (3D) Bi2O3-supported carbon fiber aerogel (Bi2O3/CF). The calcination temperature plays an important role in the crystal composition of Bi species and the specific surface area of the aerogel. When the calcination temperature is 800 °C, the Bi2O3/CF product exhibits the highest tetracycline (TC) removal efficiency, including large adsorbability and superior photocatalytic activity. Furthermore, its 3D porous network architecture provides a multidimensional open framework for the free mobility of solution and rapid diffusion of reactants and products. In the flowing system, the 3D Bi2O3/CF aerogel can implement the continuous and stable elimination of pollutants for a long time, and it does not require any separation operation. Consequently, the 3D Bi2O3/CF aerogel is expected as a promising functional material to massively remove organic pollutants from industrial wastewater.