Nanoporous Gold: From Structure Evolution to Functional Properties in Catalysis and Electrochemistry

Gold-Catalyzed Alkyne-Amine Cascade Annulations: A Modern Strategy for Azaheterocycle Construction

Gold catalysis has experienced remarkable progress over the past two decades, particularly in transformations involving alkynes. While numerous aspects of gold-catalyzed reactions have been extensively reviewed, the specific area of cascade annulations between functionalized amines and alkynes represents a distinct and rapidly developing direction that warrants focused attention. This survey collects and systematically analyzes these transformations, which have emerged as convenient synthetic strategies to diverse nitrogen heterocycles. The relevant annulations are classified firstly by the chemical nature of the amine functional substituent, and secondly by the size of the formed ring. The field under consideration bridges several fundamental and practical branches of chemistry, including catalysis, organic synthesis, medicinal chemistry, and materials science.

The influence of pressure on lithium dealloying in solid-state and liquid electrolyte batteries

Dealloying reactions underpin the operation of next-generation battery electrodes and are also a synthesis route for porous metals, but the influence of mechanical stress on these processes is not well understood. Here we investigate how the applied stack pressure affects structural evolution and electrochemical reversibility during the alloying/dealloying of Li alloy materials (Li-Al, Li-Sn, Li-In and Li-Si) using solid-state and liquid electrolytes. The extent of porosity formation during the dealloying of metals is found to be universally governed by stack pressure, with pressures of at least 20% of the yield strength required to achieve ~80% relative density. This concept is correlated to the cycling of alloy electrodes in solid-state batteries, with a yield-strength-dependent threshold pressure needed for reversible high Li-storage capacity due to densification. With this understanding, we design Al and Si anodes with a densified interfacial layer enabling stable cycling at low stack pressures (2 MPa), providing guidance towards practical high-energy solid-state batteries.

Nanoporous Plasmonic Microneedle Arrays Induced High-Efficiency Intracellular Delivery of Metabolism Regulating Protein

Patterned micro/nanostructure arrays have shown the potential to effectively regulate cellular behavior, and their unique microstructure may address the limitations of conventional pore materials, leading to novel phenomena. In this work, a large-area gold micro/nano-array substrate with an average hole of ≈32 nm is designed and extensively screened. Precisely engineered nanopores on the substrate can effectively improve photothermal conversion efficiency, and instant heat dissipation in the absence of laser irradiation. The mesoporous arrays are fabricated by hybrid lithography, offering advantages such as simple processing, high reproducibility, and immense commercial potential. Notably, its heating rate is as rapid as ≈45 K µs-1 at low power levels, with the cooling duration reduced to ≈50 µs after the laser irradiation. Metabolism regulatory proteins such as cytochrome C (CytoC) and β-galactosidase (β-gal) can be efficiently introduced into the U87 cell model without inducing phototoxicity or protein inactivation, maintaining catalytic activity to modulate the cellular metabolic state. This delivery platform based on transient nano-cyclones stimulating cell perturbations can be further expanded through modulated microstructures, such as delivering functional proteins or biomolecules for efficient intracellular regulation, cellular transfection, and in the future application as a potential high-throughput screening tool for clustered regularly interspaced short palindromic repeats (CAR-T) biopharmaceutical and clustered regularly interspaced short palindromic repeats (CRISPR) technologies.

Interplay of Surface Charge and Pore Characteristics in the Immobilization of Lactate Oxidase on Bulk Nanoporous Gold Electrodes

Immobilization of enzymes on (nano)porous metal carriers provides the foundation for an advanced design of bioelectrodes suitable for catalysis and sensing. However, interactions upon adsorption are still poorly understood, and so the efficient coupling of the enzymes to the electrode surface remains one of the major challenges. Here, we present a comprehensive study of the immobilization behavior of Aerococcus viridans l-lactate oxidase (LOx) on nanoporous gold (npAu) in dependence of electrode modification with differently charged self-assembled monolayers (SAMs). The highest activity (up to 14 U/g) and electrocatalytic response (sensitivity of 3.9 μA mM-1) were observed for a sulfonate-terminated SAM. This is contrary to enzyme behavior on conventional polymer carriers, and thus, the effect is specific to the metal electrodes. We propose the capture of the negatively charged LOx in a dense counterion layer in close proximity to the strongly negatively charged gold surface. Adsorption on positively charged amine-terminated SAMs resulted in a similar immobilization yield but gave much lower activity (4-fold). Importantly, the effect of the sulfonate SAM was strongly dependent on the npAu electrode pore size: the highest LOx activity (in U/cm2) was found with pores (diameter of ∼170 nm) supposedly large enough to facilitate enzyme diffusion into the porous structure during immobilization. Electrochemical sensing of H2O2 produced by the LOx reaction showed a 2.5-fold higher sensitivity for l-lactate on the negatively charged surface. Lixiviation studies supported the proposed layer capture and revealed a faster decline in the electrode activity with sulfonate surface modification. Collectively, the present study reveals enhanced activity of LOx on sulfonate-charged gold surfaces and a strong pore size dependence. These findings deepen the understanding of the immobilization behavior of LOx on charged nanoporous metals and have importance for the advanced design of enzyme electrodes.

Electrochemically Induced Nanoscale Stirring Boosts Functional Immobilization of Flavocytochrome P450 BM3 on Nanoporous Gold Electrodes

Enzyme-modified electrodes are core components of electrochemical biosensors for diagnostic and environmental analytics and have promising applications in bioelectrocatalysis. Despite huge research efforts spanning decades, design of enzyme electrodes for superior performance remains challenging. Nanoporous gold (npAu) represents advanced electrode material due to high surface-to-volume ratio, tunable porosity, and intrinsic redox activity, yet its coupling with enzyme catalysis is complex. Here, the study reports a flexible-modular approach to modify npAu with functional enzymes by combined material and protein engineering and use a tailored assortment of surface and in-solution methodologies for characterization. Self-assembled monolayer (SAM) of mercaptoethanesulfonic acid primes the npAu surface for electrostatic adsorption of the target enzyme (flavocytochrome P450 BM3; CYT102A1) that is specially equipped with a cationic protein module for directed binding to anionic surfaces. Modulation of the SAM surface charge is achieved by electrochemistry. The electrode-adsorbed enzyme retains well the activity (33%) and selectivity (complete) from in-solution. Electrochemically triggered nanoscale stirring in the internal porous network of npAu-SAM enhances speed (2.5-fold) and yield (3.0-fold) of the enzyme immobilization. Biocatalytic reaction is fueled from the electrode via regeneration of its reduced coenzyme (NADPH). Collectively, the study presents a modular design of npAu-based enzyme electrode that can support flexible bioelectrochemistry applications.

Exploring the diffusion of DNA strands into nanoporous structures for establishing a universal electrochemical biosensor

The development of universal electrochemical sensing platforms with high sensitivity and specificity is of great significance for advancing practical disease diagnostic methods and devices. Exploring the structural properties of electrode materials and their interaction with biomolecules is essential to developing novel and distinctive analytical approaches. Here, we innovatively investigated the effect of DNA length and configuration on DNA molecule transfer into the nanostructure of a nanoporous gold (NPG) electrode. The NPG electrode can not only distinguish and quantify short DNA strands but can also prevent the diffusion of long DNA, thereby minimizing or eliminating background interference. Leveraging these findings, we developed a universal DNA-based NPG electrochemical biosensing platform for the detection of different types of biomolecules. As a proof-of-concept, this sensing platform was integrated with nuclease-assisted target-recycling recognition and amplification reactions to achieve sensitive and specific detection of single-stranded DNA, microRNA-21, and carcino-embryonic antigen, with detection limits of 4.09, 27.4, and 0.28 fM, respectively. The demonstrated universality, sensitivity, specificity, and capability for analyzing complex samples ensure a comprehensive and robust detection approach for nucleic acid-based molecular diagnosis.

A Y-Shaped Peptide-Based Antifouling Electrochemical Aptasensor for Sensitive Aflatoxin B1 Detection in Food

Conquering surface fouling of sensors caused by nonspecific adsorption and accumulation of foulants in a food matrix is of significance in accurate food safety analysis. Herein, an antifouling electrochemical aptasensor based on a Y-shaped peptide and nanoporous gold (NPG) for aflatoxin B1 detection in milk, tofu, and rice flour was proposed. The self-designed Y-shaped peptide involves an anchoring segment (-C), a support structure (-PPPP-), and an antifouling domain with two branches (-EK(KSRE)DER-) inspired by two bioactive peptides. NPG offers not only good electroconductibility but also anchor sites for peptides and aptamers. The antifouling surface can effectively resist fouling from single protein and carbohydrate solutions and even real food. The proposed aptasensor achieves sensitive detection with a low limit of detection of 0.26 pg mL-1 (linear range: 0.001-10 ng mL-1) and accurate analysis with minimal sample pretreatment (recoveries: 91.0-110.8%), offering a potential sensing platform to lower matrix interference.

Monolithic gold saturated on nanoporous gold@mirror template for highly reliable and fast surface-enhanced Raman scattering detection

The primary challenge hindering the broad application of surface-enhanced Raman scattering (SERS) is the variability in substrate performance due to site differences, leading to unstable detection results. Thus, the current work reports the constant potential deposition of gold (Au) nanostructure on a hybrid nanoporous gold (npAu)-Au mirror template to generate highly stable monolithic Au-saturated npAu@Au-mirror substrate. By systematically adjusting electrochemical variables, different sizes, shapes, and nanogaps of Au nanostructure are generated with high-intensity electromagnetic field regions (hot junctions) for enhanced SERS response. The resulting reproducible and enhanced SERS response of the Au-saturated npAu@Au-mirror mainly originates from i) the precise control of potential and accumulation time (-0.3 V and t = 100 s) to generate uniform and symmetric particle size, dispersion, and nanogaps formation through the reduction, nucleation, and growth of Au nanoparticles; ii) free selective dealloying and complete immersion of Au50Ag50 to ensure identical conditions across the alloy surface. The metrics for substrate efficiency were evaluated for reproducibility (n = 100, RSD = 14.22%), signal stability (storage time 25 days and variation in batches and multiple synthesis runs) and enhancements (enhancement factor∼1.3 × 107). The substrate was extended for the rapid and direct malachite green detection in fish samples with a detection limit of 1.7 × 10-9 mol L-1 and good recoveries (96.69 ± 2.18%∼98.51 ± 0.63%). The monolithic Au-saturated npAu@Au-mirror substrate might be implemented for routine analysis of other target types in food safety-related applications.

Homologous Temperature Regulated Hierarchical Nanoporous Structures by Dealloying

Nanoporous metals, fabricated via dealloying, offer versatile applications but are typically limited to unimodal porous structures, which hinders the integration of conflicting pore-size-dependent properties. A strategy is presented that exploits the homologous temperature (TH)-dependent scaling of feature sizes to generate hierarchical porous structures through multistep dealloying at varied TH levels, adjusted by altering dealloying temperatures or the material melting points. This technique facilitates the creation of monolithic architectures of bimodal porous nickel and trimodal porous carbon, each characterized by well-defined, self-similar bicontinuous porosities across distinct length scales. These materials merge extensive surface area with efficient mass transport, showing improved current delivery and rate capabilities as electrodes in electrocatalytic hydrogen production and electrochemical supercapacitors. These results highlight TH as a unifying parameter for precisely tailoring feature sizes of dealloyed nanoporous materials, opening avenues for developing materials with hierarchical structures that enable novel functionalities.

A highly structured Au-grafted nanoporous gold for surface-enhanced Raman scattering detection of ferbam

The expansive potential of surface-enhanced Raman scattering (SERS) has been well-established; however, the primary bottleneck hindering its routine analytical and commercial implementation is the poor signal reproducibility and challenges in substrate fabrication. Thus, the current work attempts to synthesize a scalable and reproducible nanoporous gold (npAu) decorated with gold (Au) nanoparticles to generate a highly structured Au@npAu nanocomposite. The substrate fabrication completes via three distinct routes: i) selective dealloying to form npAu on the Au film, ii) the fast deposition (i-t = -0.8 V, t = 10.0 s) of Au atoms across the npAu surface, and finally iii) the precise growth control of the generated Au@npAu by a series of by oxidation-reduction cycles (-0.03 to -0.4 V for 80.0 segments at ν = 50.0 mVs-1). The simulations of the dealloyed npAu and the final Au@npAu nanocomposite showed that the reduced interparticle spacing and ligament size in the Au@npAu nanocomposite is crucial for forming abundant "hot spot" regions with highly concentrated electromagnetic fields. The Au@npAu substrate reproducibility was assessed on 400.0 sites for SERS spectral acquisition with a relative standard deviation of 9.22 %. Furthermore, the Au@npAu was checked under different preparation batches for intra- and inter-day analysis and storage for 20.0 days with good stability. Finally, the substrate was checked for direct SERS detection of ferbam residues with a 4.34 × 10-9 mol L-1 sensitivity and examined in real samples with satisfactory recoveries (97.63 ± 1.95%-99.16 ± 0.24 %). This work offers a promising avenue towards highly reproducible, scalable and universal Au@npAu SERS substrate fabrication in diverse SERS-related applications.

Atomic Level Understanding of the Structural Stability and Catalytic Activity of Nanoporous Gold/Titania Cluster Inverse Catalysts at Ambient and High Temperatures

Nanoporous gold (NPG) exhibits exceptional catalytic performance at low temperatures, but its activity declines at elevated temperatures due to structural coarsening. Loading metal oxide nanoparticles onto NPG can enhance its catalytic activity at high temperatures. In this work, we used NPG-supported titania nanoparticles as a model system (denoted as Ti2O4/NPG) to study their catalytic activity at ambient and high temperatures with CO oxidation as a probe reaction by density functional theory (DFT) calculation and ab initio molecular dynamics (AIMD) simulations. The possible factors that may affect the CO oxidation reaction pathways and energy profiles on the Ti2O4/NPG, such as oxygen vacancies; silver impurities; Mars-van Krevelen (MvK), Eley-Rideal (ER), or trimolecular Eley-Rideal (TER) mechanisms; and catalytic active sites, were comprehensively investigated. The results showed that reaction energy barriers on Ti2O4/NPG were not significantly decreased compared to the pristine NPG, indicating that their catalytic activities at ambient temperature were comparable. At the evaluated temperature (400 °C), the Ti2O4/NPG exhibited superior thermal stability and maintained its active sites, while the NPG reduced active sites due to surface coarsening. The strong oxide-metal interaction (SOMI) effect between the NPG and Ti2O4 nanoparticles is found to be a main factor for the high structural stability and catalytic activity at high temperatures.

Organic and Metal-Organic Polymer-Based Catalysts-Enfant Terrible Companions or Good Assistants?

This overview provides insights into organic and metal-organic polymer (OMOP) catalysts aimed at processes carried out in the liquid phase. Various types of polymers are discussed, including vinyl (various functional poly(styrene-co-divinylbenzene) and perfluorinated functionalized hydrocarbons, e.g., Nafion), condensation (polyesters, -amides, -anilines, -imides), and additional (polyurethanes, and polyureas, polybenzimidazoles, polyporphyrins), prepared from organometal monomers. Covalent organic frameworks (COFs), metal-organic frameworks (MOFs), and their composites represent a significant class of OMOP catalysts. Following this, the preparation, characterization, and application of dispersed metal catalysts are discussed. Key catalytic processes such as alkylation-used in large-scale applications like the production of alkyl-tert-butyl ether and bisphenol A-as well as reduction, oxidation, and other reactions, are highlighted. The versatile properties of COFs and MOFs, including well-defined nanometer-scale pores, large surface areas, and excellent chemisorption capabilities, make them highly promising for chemical, electrochemical, and photocatalytic applications. Particular emphasis is placed on their potential for CO2 treatment. However, a notable drawback of COF- and MOF-based catalysts is their relatively low stability in both alkaline and acidic environments, as well as their high cost. A special part is devoted to deactivation and the disposal of the used/deactivated catalysts, emphasizing the importance of separating heavy metals from catalysts. The conclusion provides guidance on selecting and developing OMOP-based catalysts.

Spiers Memorial Lecture: New directions in molecular scattering

The field of molecular scattering is reviewed as it pertains to gas-gas as well as gas-surface chemical reaction dynamics. We emphasize the importance of collaboration of experiment and theory, from which new directions of research are being pursued on increasingly complex problems. We review both experimental and theoretical advances that provide the modern toolbox available to molecular-scattering studies. We distinguish between two classes of work. The first involves simple systems and uses experiment to validate theory so that from the validated theory, one may learn far more than could ever be measured in the laboratory. The second class involves problems of great complexity that would be difficult or impossible to understand without a partnership of experiment and theory. Key topics covered in this review include crossed-beams reactive scattering and scattering at extremely low energies, where quantum effects dominate. They also include scattering from surfaces, reactive scattering and kinetics at surfaces, and scattering work done at liquid surfaces. The review closes with thoughts on future promising directions of research.

Two-dimensional single-crystalline mesoporous high-entropy oxide nanoplates for efficient electrochemical biomass upgrading

Mesoporous single crystals have received more attention than ever in catalysis-related applications due to their unique structural functions. Despite great efforts, their progress in engineering crystallinity and composition has been remarkably slower than expected. In this manuscript, a template-free strategy is developed to prepare two-dimensional high-entropy oxide (HEO) nanoplates with single-crystallinity and penetrated mesoporosity, which further ensures precise control over high-entropy compositions and crystalline phases. Single-crystalline mesoporous HEOs (SC-MHEOs) disclose high electrocatalytic performance in 5-hydroxymethylfurfural oxidation reaction (HMFOR) for efficient biomass upgrading, with remarkable HMF conversion of 99.3% and superior 2,5-furandicarboxylic acid (FDCA) selectivity of 97.7%. Moreover, with nitrate reduction as coupling cathode reaction, SC-MHEO realizes concurrent electrosynthesis of value-added FDCA and ammonia in the two-electrode cell. Our study provides a powerful paradigm for producing a library of novel mesoporous single crystals for important catalysis-related applications, especially in the two-electrode cell.

Hierarchical Carbon Nanocages as Superior Supports for Photothermal CO2 Catalysis

The exploitation of hierarchical carbon nanocages with superior light-to-heat conversion efficiency, together with their distinct structural, morphological, and electronic properties, in photothermal applications could provide effective solutions to long-standing challenges in diverse areas. Here, we demonstrate the discovery of pristine and nitrogen-doped hierarchical carbon nanocages as superior supports for highly loaded, small-sized Ru particles toward enhanced photothermal CO2 catalysis. A record CO production rate of 3.1 mol·gRu-1·h-1 with above 90% selectivity in flow reactors was reached for hierarchical nitrogen-doped carbon-nanocage-supported Ru clusters under 2.4 W·cm-2 illumination without external heating. Detailed studies reveal that the enhanced performance originates from the strong broadband sunlight absorption and efficient light-to-heat conversion of nanocage supports as well as the excellent intrinsic catalytic reactivity of sub-2 nm Ru particles. Our study reveals the great potential of hierarchical carbon nanocages in photothermal catalysis to reduce the fossil fuel consumption of various industrial chemical processes and stimulates interest in their exploitation for other demanding photothermal applications.

Tuning Electrocatalytic Activities of Dealloyed Nanoporous Catalysts by Macroscopic Strain Engineering

It is technically challenging to quantitatively apply strains to tune catalysis because most heterogeneous catalysts are nanoparticles, and lattice strains can only be applied indirectly via core-shell structures or crystal defects. Herein, we report quantitative relations between macroscopic strains and hydrogen evolution reaction (HER) activities of dealloyed nanoporous gold (NPG) by directly applying macroscopic strains upon bulk NPG. It was found that macroscopic compressive strains lead to a decrease, while macroscopic tensile strains improve the HER activity of NPG, which is in line with the d-band center model. The overpotential and onset potential of HER display approximately a linear relation with applied macroscopic strains, revealing an ∼2.9 meV decrease of the binding energy per 0.1% lattice strains from compressive to tensile. The methodology with the high strain sensitivity of electrocatalysis, developed in this study, paves a new way to investigate the insights of strain-dependent electrocatalysis with high precision.

Tuning the morphology and chemical distribution of Ag atoms in Au rich nanoparticles using electrochemical dealloying

Dealloying of Ag-Au alloy nanoparticles (NPs) strongly differs from the corresponding bulk alloy materials. Here, we have investigated the effects of potentiodynamic and potentiostatic dealloying on structure and distribution of residual Ag atoms for Au rich NPs. Two different sizes of Ag rich alloy NPs, 77 ± 26 nm Ag77Au23 and 12 ± 5 nm Ag86Au14, were prepared. 77 nm Ag77Au23 NPs form a homogeneous alloy, while 12 nm Ag86Au14 NPs show an Ag rich shell-Au rich core arrangement. The two groups of as-prepared NPs were dealloyed either under potentiodynamic (0.2-1.3 VRHE) or potentiostatic (0.9, 1.2, and 1.6 VRHE) conditions in 0.1 M HClO4. For the initial 77 nm Ag77Au23 NPs, both dealloying protocols lead to pore evolution. Interestingly, instead of homogenous Ag distribution, numerous Ag rich regions form and locate near the pores and particle edges. The critical dealloying potential also differs by ∼500 mV depending on the dealloying method. The initial 12 nm Ag86Au14 NPs remain dense and solid, but Ag distribution and thickness of the Au passivation layer vary between both dealloying protocols. When the Au passivation layer is very thin, the residual Ag atoms tend to segregate to the particle surface after dealloying. Due to the size effect, small NPs are less electrochemically stable and show a lower critical dealloying potential. In this systematic study, we demonstrate that the mobility of Au surface atoms and dealloying conditions control the structure and residual Ag distribution within dealloyed NPs.

Nanoporous Au Behavior in Methyl Orange Solutions

Nanoporous (NP) gold, the most extensively studied and efficient NP metal, possesses exceptional properties that make it highly attractive for advanced technological applications. Notably, its remarkable catalytic properties in various significant reactions hold enormous potential. However, the exploration of its catalytic activity in the degradation of water pollutants remains limited. Nevertheless, previous research has reported the catalytic activity of NP Au in the degradation of methyl orange (MO), a toxic azo dye commonly found in water. This study aims to investigate the behavior of nanoporous gold in MO solutions using UV-Vis absorption spectroscopy and high-performance liquid chromatography. The NP Au was prepared by chemical removal of silver atoms of an AuAg precursor alloy prepared by ball milling. Immersion tests were conducted on both pellets and powders of NP Au, followed by examination of the residual solutions. Additionally, X-ray photoelectron spectroscopy and electrochemical impedance measurements were employed to analyze NP Au after the tests. The findings reveal that the predominant and faster process involves the partially reversible adsorption of MO onto NP Au, while the catalytic degradation of the dye plays a secondary and slower role in this system.

Liposome-Templated Green Synthesis of Mesoporous Metal Nanostructures with Universal Composition for Biomedical Application

Porous noble metal nanoparticles have received particular attention recently for their unique optical, thermal, and catalytic functions in biomedicine. However, limited progress has been made to synthesize such porous metallic nanostructures with large mesopores (≥25 nm). Here, a green yet facile synthesis strategy using biocompatible liposomes as templates to mediate the formation of mesoporous metallic nanostructures in a controllable fashion is reported. Various monodispersed nanostructures with well-defined mesoporous shape and large mesopores (≈ 40 nm) are successfully synthesized from mono- (Au, Pd, and Pt), bi- (AuPd, AuPt, AuRh, PtRh, and PdPt), and tri-noble metals (AuPdRh, AuPtRh, and AuPdPt). Along with a successful demonstration of its effectiveness in synthesis of various mesoporous nanostructures, the possible mechanism of liposome-guided formation of such nanostructures via time sectioning of the synthesis process (monitoring time-resolved growth of mesoporous structures) and computational quantum molecular modeling (analyzing chemical interaction energy between metallic cations and liposomes at the enthalpy level) is also revealed. These mesoporous metallic nanostructures exhibit a strong photothermal effect in the near-infrared region, effective catalytic activities in hydrogen peroxide decomposition reaction, and high drug loading capacity. Thus, the liposome-templated method provides an inspiring and robust avenue to synthesize mesoporous noble metal-based nanostructures for versatile biomedical applications.

Cocontinuous Nanostructures by Microphase Separation of Statistically Cross-Linked Polystyrene/Poly(2-vinylpyridine) Networks

Cocontinuous polymeric nanostructures have drawn considerable attention due to their ability to combine distinct, percolation-dependent properties of two different polymer domains. Randomly end-linked copolymer networks (RECNs) have previously been shown to support the formation of disordered cocontinuous nanostructures across wide composition windows in a robust way. However, achieving highly efficient linking of telechelic polymers with excellent end-group fidelity often requires complex synthetic routes. As an alternative, we study here statistically cross-linked copolymer networks (SCCNs) composed of polystyrene and poly(2-vinylpyridine) (PS and P2VP) with cross-linkable allyl pendent groups that are conveniently synthesized by controlled radical copolymerization. Via selective extraction of P2VP, coupled with gravimetry, small-angle X-ray scattering, and electron microscopy, we find disordered cocontinuous phases across wide composition ranges (up to ≈ 35 wt %), approaching values previously determined for RECNs. Remarkably, even for samples that appear to exhibit full percolation, a substantial fraction of P2VP (≈ 20-30 wt %) cannot be removed, which we ascribe to short strands between nearby cross-linkers that are physically embedded within PS domains. The resulting PS porous monoliths with residual surface P2VP layers enable facile surface modification to resist protein adsorption and templating of porous gold nanostructures.

Gold(I)-Organic Frameworks as Catalysts for Carboxylation of Alkynes with CO2

Construction of gold-based metal-organic frameworks (Au-MOFs) would bring the merits of gold chemistry into MOFs. However, it still remains challenging because gold cations are easily reduced to metallic gold under solvothermal conditions. Herein, we present the first example of Au-MOFs prepared from the networking of cyclic trinuclear gold(I) complexes by formal transimination reaction in a rapid (<15 min) and scalable (up to 1 g) fashion under ambient condition. The Au-MOFs feature uniform porosity, high crystallinity, and superior chemical stability toward base (i.e., 20 M NaOH). With open Au(I) sites in the skeleton, the Au-MOFs as heterogeneous catalysts delivered good performance and substrate tolerance for the carboxylation reactions of alkynes with CO2. This work demonstrates a facile approach to reticularly synthesize Au-MOFs by combining the coordination and dynamic covalent chemistry.

Liquid-Metal Solvents for Designing Hierarchical Nanoporous Metals at Low Temperatures

Metallic nanoarchitectures hold immense value as functional materials across diverse applications. However, major challenges lie in effectively engineering their hierarchical porosity while achieving scalable fabrication at low processing temperatures. Here we present a liquid-metal solvent-based method for the nanoarchitecting and transformation of solid metals. This was achieved by reacting liquid gallium with solid metals to form crystalline entities. Nanoporous features were then created by selectively removing the less noble and comparatively softer gallium from the intermetallic crystals. By controlling the crystal growth and dealloying conditions, we realized the effective tuning of the micro-/nanoscale porosities. Proof-of-concept examples were shown by applying liquid gallium to solid copper, silver, gold, palladium, and platinum, while the strategy can be extended to a wider range of metals. This metallic-solvent-based route enables low-temperature fabrication of metallic nanoarchitectures with tailored porosity. By demonstrating large-surface-area and scalable hierarchical nanoporous metals, our work addresses the pressing demand for these materials in various sectors.