Sub-1 nm nanowires (SNWs) exhibit exceptional physicochemical properties. However, their fabrication into three-dimensional macroscopic materials for practical applications remains a significant challenge. Herein, we report a polarity-induced hierarchical assembly strategy combined with freeze-casting to fabricate silanized SNW aerogels (Si–SNWAs) using GdOOH SNWs as building blocks. Through polarity induction and methyltrimethoxysilane mediation, SNWs hierarchically assemble into micron-scale tertiary fibers, forming continuous 3D porous networks. The resulting Si–SNWAs feature ultralow density, superhydrophobicity, and excellent mechanical flexibility and stability, outperforming unmodified SNWAs in terms of cyclic compression and bending resistance. Furthermore, Si–SNWAs exhibit not only passive thermal management capability but also favorable hydrophobic–oleophilic performance, with an oil adsorption capacity of 19–29 g g−1 and satisfactory reusability. This strategy is also universal for multicomponent rare earth SNW coassembly, offering a flexible route for designing SNW-based aerogel materials.

The fabrication of uncontaminated single-walled carbon nanotube (SWNT) horizontal arrays is crucial for the development of carbon-based nanoelectronics. However, chemical vapor deposition (CVD) using transition metal catalysts, one of the main methods for preparing SWNT arrays, leaves a significant amount of metal impurities. Here, we report a synergistic thermophoresis-anchoring strategy to prepare uniformly dispersed and size- controllable non-metal SiOx catalysts for the growth of horizontal SWNT arrays. The pyrolysis of silicon-based precursors generates an abundant supply of SiOx particles, which are deposited bottom-up onto the quartz substrate due to the thermal buoyancy induced by a rapid temperature increase. Meanwhile, Surface reconstruction promoted by mechanical force creates numerous anchoring sites on the quartz substrate. This facilitates the capture of catalysts and suppresses their migration and aggregation, thereby promoting the uniform deposition of small-sized catalysts. Consequently, SWNT arrays with a density of 9 tubes per micron are synthesized using these nonmetal SiOx catalysts. Importantly, Raman spectroscopy and electrical characterization reveal a semiconductor ratio of up to 94 % for the directly grown SWNT arrays, which is attributed to an in situ etching mechanism within the confined space. This work provides a viable way to promote the practical application of next-generation carbon-based nanodevices.

Metal aerogels are emerging porous materials composed entirely of nanostructured metals, which manifest broad prospects in diverse fields. Particularly, multimetallic aerogels (MMAs) receive increasing attention due to their widely tunable properties stimulated by the synergy of multiple metals. However, the investigation of multimetallic effects in MMAs is predominantly restricted to optimizing their application performances. Here, the untrivial multimetallic effects on the synthetic aspect are discovered, and the underlying mechanisms are unveiled, offering new perspectives for manipulating the sol-gel process and tuning the ligament size (dL) of MMAs by designing the average bulk density (rab) and atomic radius (ra) mismatch. Moreover, a sedimentation-based non-destructive method is established, which solves the long-lasting challenge of preparing intact metal-gel-based electrocatalysts and yields record-high performances toward alcohol oxidation reactions.

Solar interfacial water evaporation is a promising approach for freshwater production, yet its performance is fundamentally constrained by a trade-off: heat confinement demands minimal surface water, while salt removal requires abundant water supply. Most designs favor one aspect, sacrificing either evaporation rate or long-term stability. Here, we present an integrally synthesized triple-layered aerogel evaporator that overcomes this bottleneck. Distinct internal pore structures generate Laplace pressure gradients, precisely regulating water distribution and transport to form a stable solid-liquid-vapor triple-phase interface. This configuration simultaneously localizes heat, accelerates vapor generation, and continuously removes surface salt. As a result, the system achieves 3.67 kg m-2 h-1 under 1-sun illumination and retains 100% performance over 50 h of continuous saline operation. Our design resolves the intrinsic efficiency-durability conflict, offering a robust and scalable platform for high-performance solar desalination.

Porous metals combine the physicochemical properties of metals and structural features of porous materials, which are characterized as a special class of materials promising in various fields such as tissue engineering, energy storage and conversion, electronics, and sensing. Among diverse fabrication approaches, freezing-mediated synthesis (e.g., freeze-casting and freeze-thawing) stands out due to its strong controllability over meso-to-macroscales as well as environmental friendliness. Many efforts have been made in the past few decades, yielding a library of porous metals featuring different building blocks (feature size and dimension), morphologies, and compositions by identifying and optimizing synthetic parameters. However, a deep understanding of the ice-matter interactions is limited, which becomes more pronounced when the processed system transforms from micrometer to nanometer size. Therefore, an overview and deep analysis for the freezing-mediated fabrication of porous metals are essential. This review first introduces the history of freezing-mediated synthesis of porous metals, followed by the fundamentals of the freezing process and design strategies. Afterward, the freezing-mediated fabrication of porous metals is summarized from the aspect of their building blocks, followed by the application explorations of those special-structure metals. Finally, the challenges and opportunities are concluded to guide future research in designing advanced porous metals by freezing-based approaches.

As one of the latest members in the aerogel family, metal aerogels (MAs) appear to be promising materials entirely structured from nanosized metals. The combined attributes of nanometals and aerogels render them a special class of porous materials with vast potential in diverse fields. Growing environmental concerns have spurred interest in MAs for environmental remediation. Although the special features of MAs endow them with exceptional performance and multiple functions, research in environmental remediation is in its infancy, and a systematic summarization is lacking. This manuscript gives an overview of the progress and future prospects of MAs for environmental remediation. After briefing on the typical properties and mainstream synthesis strategies, the environmental application of MAs is elaborated from aspects of pollutant detection and elimination. Finally, the current challenges and future opportunities are concluded, offering a guideline to rationally design MAs for environmental remediation.

Noble metal aerogels (NMAs) are typically assembled from metal nanoparticles, thus combining the physicochemical properties of nanostructured metals with the self-standing porous architecture of aerogels. NMAs therefore have potential in catalysis, sensing and other applications where the controlled manipulation of their structure and composition facilitates their use in fundamental and applied sciences. However, their preparation remains challenging due to the particular gelation behavior displayed by metal systems. Here we detail the step-by-step instructions for the controlled synthesis of NMAs using salts, including reductive sodium borohydride and common salts such as sodium chloride. This strategy can rapidly synthesize NMAs with customizable ligament sizes (from <5 nm to >100 nm) and element distribution at room temperature (20–25 °C). The key stage of the approach is the control over the anisotropic assembly behavior of metal nanoparticles by tuning their interactions with ions/ligands. The synthesis conditions and procedures are elaborated to ensure reproducibility. We demonstrate the fabrication of seven single-component NMAs and over ten multicomponent NMAs, along with their corresponding characterizations and electrocatalytic applications. The fabrication period of noble metal hydrogels is 7–15 h, which can be shortened to a few minutes by introducing disturbances such as stirring. The subsequent purification time is ~48 h, the solvent exchange time is ~16 h and the drying time is 12–24 h. The total duration is 4–5 d. The procedure is suitable for users with expertise in chemistry, materials science and other related disciplines. A protocol describing the fabrication of seven single-component noble metal aerogels and over ten multicomponent noble metal aerogels, their characterizations and their electrocatalytic applications.

High-entropy alloys (HEAs) are usually synthesized by stabilizing thermodynamically metastable structures from high temperatures. Here we present a bilayer ice recrystallization approach performed at subzero temperatures to synthesize HEA nanoparticles or aerogels with up to 11 metal elements. We found that, below 0 °C, premelted ice channels can regulate the uniform emission of metal salts and reductants to form HEA seeds. The seeds function as anti-icing agents akin to antifreeze proteins, promoting uniform element mixing and assembly at ice grain boundaries to form HEA nanoparticles or HEA aerogels. In addition, by introducing an arbitrary template, we synthesized nanometre-thick uniform HEA coatings on diverse metal or alloy nanoparticles and macroscale aerogels. The bilayer ice recrystallization method demonstrates the application of ice chemistry for the synthesis of high-entropy-based materials with hierarchical architectures. High-entropy alloy (HEA) nanoparticles, self-supporting HEA aerogels and HEA coatings with up to 11 metal elements and uniform elemental distributions have been synthesized at subzero temperatures using a bilayer ice recrystallization method. The process is observed by cryo-transmission electron microscopy and fused multimodal electron tomography.

Low-dimensional metallic nanomaterials feature inherent quantum confinement effects, which are regarded as promising building blocks for functional materials with versatile tunable properties. However, manipulating the dimensionality of nano-building blocks (referred to as microdimension) for metal aerogels (MAs), a class of emerging porous materials, remains a great challenge. Here, a universal freezing-mediated assembly strategy based on ice chemistry is demonstrated, yielding a wealth of MAs with customizable microdimensions (0D, 1D, and 2D) and compositions by one-pot synthesis. The mechanism of microdimension control is comprehensively deciphered, which relies on the leveraged engulfment and extrusion of metal nanoparticles by regulating the ice chemistry. The microdimension-dictated applications of MAs are unveiled accordingly exemplified by electrocatalysis and shining luxuries. This study not only provides a new dimension for material design but also opens up exciting possibilities for unlocking untouched application fields of aerogels.

As a well‐known coin metal, silver (Ag) stands out for its unique plasmonic properties and the lowest cost among all noble metals. However, the sol–gel chemistry of the Ag system remains undeciphered, challenging the rational design of Ag aerogels. Additionally, the chemical reactivity of Ag is often neglected in designing noble metal aerogels (NMAs), leaving significant potential untapped for advanced applications. Here, versatile engineering of Ag aerogels is realized by precisely tuning metal‐ion, metal‐ligand, and metal‐metal interactions, achieving a ligament size modulation across 3 orders of magnitude and downsizing the ligament size to <10 nm. The redox potential difference (Δ E )‐driven gel‐level conversion methodology is further established by utilizing the chemical activity of Ag and the self‐healing properties of noble metal hydrogels, stepwise yielding various self‐standing and hollow‐structured Ag‐M aerogels with record‐high performance for (photo)electrocatalysis. This study not only offers guidelines for manipulating multiscale structures of broad metal aerogels but also unveils their unprecedented potential for energy‐related applications.

As rising stars of the aerogel family, metal aerogels (MAs) manifest broad prospects for combining features of nanostructured metals and aerogels. However, restricted by insufficient mechanistic understanding and limited strategies, the structure‐tailored fabrication of MAs remains challenging. Here, unveiling and utilizing the triple roles (initiator, ligand, and solvent) played by imidazolium‐based ionic liquids (ILs), a robust and universal method is developed, yielding diverse ligament‐size‐tailored MAs at ambient temperature assisted by ILs (down to 0.5 µ m , ≈7.7 × 10 −6 vol.%). Moreover, the ILs can be recovered by salt‐induced phase separation. Driven by unconventional self‐healing properties, special optical features, and abundant catalytically active sites, the tailor‐made gold aerogels are confirmed as a new generation of self‐recoverable and light‐enhanced catalysts for water remediation.

Conductive metal–organic frameworks (c‐MOFs), composed of metal nodes and redox‐active ligands, have attracted growing interest due to the coexistence of porosity and charge transport. Notably, their electrical performance is closely related to the packing and ligand oxidation state within the framework, which has rarely been explored. Typical divalent metal nodes favor saturated intralayer square‐planar coordination to ligands in a single oxidation state, thereby predetermining the framework topology. Here, we report a packing and topology control strategy, achieved by tuning the ligand oxidation state and grounded in lanthanides (e.g., Gd) versatile coordination chemistry. Diffuse reflectance spectroscopy and single‐crystal transport measurements reveal that, at low temperature, coordination of Gd 3+ with 2,3,6,7,10,11‐hexahydroxytriphenylene (HHTP) in a lower mixed oxidation state (−4 and −5) yields a more ordered porous packing (Gd 1.5 HHTP) with superior electronic transport performance. In contrast, at elevated temperature, the ligand adopts a higher oxidation state (−3), and coordination with Gd 3+ yields a densely packed structure with local coordination disorder (GdHHTP), resulting in a markedly reduced electrical conductivity. This study demonstrates ligand‐oxidation‐state tuning provides an effective strategy for the precise control of structural order and charge transport in c‐MOFs, laying a theoretical foundation for the rational design of materials with tunable electronic properties.

Metal aerogels (MAs) are emerging all-nanometal-structured self-standing porous materials featuring exceptional performances in diverse fields. They have recently been adopted as 3D surface-enhanced Raman scattering (SERS) substrates, while the less utilization of the unique porous structure leads to limited performance. Here, a fascinating compression-mediated regulation strategy is presented to largely boost the SERS performance of Au-Ag aerogels. By gently pressing, both the density of hot spots and the inter-ligament distance can be efficiently modulated, thus enabling to flexibly manipulate the SERS properties of MAs. On this basis, a record-high misfocus tolerance (similar to 8.8 mm), low detection limit (down to 0.1 nM), high stability (>1 month), reusability, and multiplex detection ability are concurrently realized. This study may point out a new direction for engineering 3D SERS substrates with tunable and exceptional performance.

Daytime radiative cooling materials exhibit huge potential for sustainable development, which can reflect sunlight and radiate heat to outer space in the main atmospheric window without energy consumption. Recently, polymer-based nanofiber membranes have been fabricated for radiative cooling, because of their easy processing and ideal optical performance. However, there exist big challenges in fabricating low-cost and environmentally friendly daytime radiative cooling materials for large-scale practical applications. In this work, we demonstrate a novel poly(vinyl alcohol)@silica (PVA@SiO2) composite membrane via typical electrospinning technology and a simple coating process. The resultant composite membrane exhibits spectral selectivity with high sunlight reflectance of ∼95.0% as well as a mid-infrared emissivity of ∼90.2%, UV protection, and hydrophobicity, endowing its excellent daytime radiative cooling effect with a temperature drop of ∼8.0 °C. The as-obtained membranes exhibit some promising future for the potential large-scale application of radiative cooling technology for energy savings.

Abnormal secretion and dysrhythmias of cortisol (CORT) are associated with various diseases such as sleep disorders, depression, and chronic fatigue. Wearable devices are a cutting-edge technology for point-of-care detection and dynamic monitoring of CORT with inspiring convenience. Herein, we developed a minimally invasive skin-worn device with the advanced integration of both interstitial fluid (ISF) sampling and target molecule sensing for simultaneous detection of CORT via a microneedle-based sensor with high sensitivity, excellent efficiency, and outstanding reproducibility. In the microneedle patch, swellable hydrogel was employed as the adsorption matrix for ISF extraction. Meanwhile, europium metal-organic frameworks (Eu-MOF) wrapped in the matrix played a vital role in CORT recognition and quantitative analysis. The wearable and label-free Eu-MOF-loaded microneedle patch exhibited high sensitivity in CORT detection with the detection limit reaching 10(-9) M and excellent selectivity. Molecular dynamics simulation-driven mechanism exploration revealed that the strong interface interaction promoted fluorescence quenching of Eu-MOF. Moreover, in vitro and in vivo investigation confirmed the feasibility and reliability of the sensing method, and excellent biocompatibility was validated. Overall, a sensitive approach based on the wearable Eu-MOF microneedle (MN) patch was established for the simultaneous detection of CORT via visible fluorescence quenching with exciting clinical-translational ability.

Noble metal aerogels (NMAs) are an emerging class of porous materials that are entirely constructed by one or more kinds of nanostructured noble metals including gold (Au), silver (Ag), palladium (Pd), platinum (Pt), ruthenium (Ru), rhodium (Rh), osmium (Os), and iridium (Ir). They feature attributes of both nanostructured noble metals (e.g., high catalytic activity, high electrical conductivity, and special optical properties) and aerogels (e.g., self-standing architecture, large specific surface area, abundant pores, and robust 3D networked structure). Therefore, since their discovery in 2009, NMAs have displayed tremendous potential in fields ranging from (electro)catalysis, battery electrodes, biosensing, plasmonic technologies, and environment remediation. However, as young materials, the investigation of NMAs is far from sufficient. Controlled synthesis is the basis for new materials that dictate how far they can reach. The sol-gel behavior of the metal system is distinct from that of conventional gel systems, thus requiring additional studies. However, the fundamental understanding of the fabrication process and thus the structure/composition control for NMAs are largely overlooked. In this context, our team has been focusing on developing effective fabrication strategies based on an in-depth understanding of the gelation mechanisms as well as the roles played by each component in the reaction. To this end, we have pioneered realizing ligament size control, unveiling the reductant chemistry, unlocking the ligand chemistry, and achieving minute-scale rapid gelation by counter-intuitionally introducing force fields. We aim to eventually realize arbitrary manipulation of the composition and structure of NMAs, which is critical for paving the way for their further development. After gaining sufficient control capacity for NMAs, then we go for exploring their applications. It is crucial to select appropriate scenarios according to their unique attributes, so as to fully exert their potential and eventually find their disruptive application directions. Inheriting features of noble metals and aerogels, NMAs possess abundant catalytic/optical active sites, high electronic/mass transfer channels, and robust and self-supported networks. In this regard, they should be suited for the (photo)electrocatalysis and detection based on surface-enhanced Raman scattering (SERS). Indeed, numerous studies have demonstrated their exceptional electrocatalytic performances towards diverse reactions such as the alcohol oxidation reaction (AOR), hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and carbon dioxide reduction reaction (CO2RR). We further pioneered incorporating light in the electrocatalytic process, opening the photoelectrocatalysis direction. Additionally, we found that Au aerogels can serve as ideal 3D SERS substrates for they feature hot spots across three dimensions, which enables their outstanding signal enhancement and misfocus tolerance. However, intentionally on-target performance optimization and the exploration of new design perspectives for NMAs are still on the way. In this account, we summarize the representative endeavors made in controlled synthesis and electrocatalysis/SERS applications of NMAs. After a brief introduction of NMAs, we will highlight the state-of-the-art understanding of the sol-gel process of metal systems, and how to achieve structure-controlled synthesis and rapid fabrication of NMAs. After narrating the progress in electrocatalysis and SERS applications, we will conclude the challenges and opportunities for these young materials.

The emerging sub-1 nm nanowires (SNWs) have received tremendous attention given their intriguing properties and broad applications attributable to their ultrasmall feature size. However, applying SNWs in microstructure-preserving macroscopic functional materials (e.g., aerogels) remains challenging because the solvents used for preparing SNWs are not compatible with conventional supercritical drying or freeze-drying techniques. In this study, the fabrication of SNW aerogels (SNWAs) is pioneered by developing a nonpolar solvent-based freeze-casting strategy. Cyclohexane, a nonpolar solvent with a freezing point (6.5 degrees C) comparable to that of water, is selected as a reaction and drying medium to assemble various SNWs. The resulting self-standing SNWAs display low density, excellent hydrophobicity and lipophilicity, and tunable luminescent color. This strategy not only introduces a new aggregation form of SNWs but also provides a creative perspective on synthesizing aerogel structures from sub-1 nm building blocks. For the first time, sub-1 nm nanowires (SNWs) are assembled as building blocks into ultralight sub-1 nm nanowire aerogels (SNWAs) using a freeze-casting process, which successfully reduces the size of the building blocks of aerogels from the nanoscale to the sub-1 nm scale. Moreover, the aerogel retains the unique subnanometer-scale properties of SNWs. image

Passive radiative cooling technology without electric consumption is an emerging sustainability technology that plays a key role in advancing sustainable development. However, most radiative cooling materials are vulnerable to outdoor contamination and thermal/UV exposure, which leads to decreased performance. Herein, we report a hierarchically structured polyimide/zinc oxide (PINF/ZnO) composite membrane that integrates sunlight reflectance of 91.4% in the main thermal effect of the solar spectrum (0.78-1.1 mu m), the mid-infrared emissivity of 90.0% (8-13 mu m), UV shielding performance, thermal resistance, and ideal hydrophobicity. The comprehensive performance enables the composite membrane to yield a temperature drop of similar to 9.3 degrees C, compared to the air temperature, under the peak solar irradiance of similar to 800 W m(-2). In addition, the temperature drop of as-obtained composite membranes after heating at 200 degrees C for 6 h in a nitrogen/air atmosphere can be well maintained at similar to 9.0 degrees C, demonstrating their ideal radiative cooling effect in a high-temperature environment. Additionally, the PINF/ZnO composite membrane shows excellent chemical durability after exposure to the outdoor environment. This work provides a new strategy to integrate chemical durability and thermal resistance with radiative cooling, presenting great potential for passive radiative cooling materials toward practical applications in harsh environments.

Horizontal arrays of single-walled carbon nanotubes (SWCNTs) have shown immense potential for application in emerging devices due to their excellent electrical and thermal properties. The direct growth of SWCNT arrays using high-activity metal catalysts is one of the promising methods to approach the mass production of dense SWCNT arrays. However, an inevitable obstacle lies in the post-purification of metal residual. Herein, a sowing strategy to prepare size-tunable potassium chloride (KCl) catalysts for the efficient growth of the SWCNT array with a density of 10 tubes per micron is reported. Through a controllable etching process, numerous surface defects (e.g., vacancies and kinks) are uniformly generated on the substrate as seed pit-like sites for the accommodation and anchoring of catalysts. The well-distributed KCl catalysts with a homogeneous size of approximate to 1.4 nm enable the growth of approximate to 1.3 nm SWCNTs through a vapor-liquid-solid mechanism. Importantly, 94 at.% KCl catalysts can be dramatically removed through a simple water-washing process, thus leaving contamination-free SWCNT arrays behind. Interestingly, 85% of nanotubes show metallic properties, which is demonstrated by the combination of electrical characterization and the multi-laser Raman spectroscopy. This sowing strategy contributes to the direct growth of uncontaminated high-density SWCNT arrays.