Recent Advances in Environmentally Friendly Dual-crosslinking Polymer Networks.

Environmentally friendly crosslinked polymer networks feature degradable covalent or non-covalent bonds, with many of them manifesting dynamic characteristics. These attributes enable convenient degradation, facile reprocessibility, and self-healing capabilities. However, the inherent instability of these crosslinking bonds often compromises the mechanical properties of polymer networks, limiting their practical applications. In this context, environmentally friendly dual-crosslinking polymer networks (denoted EF-DCPNs) have emerged as promising alternatives to address this challenge. These materials effectively balance the need for high mechanical properties with the ability to degrade, recycle, and/or self-heal. Despite their promising potential, investigations into EF-DCPNs remain in their nascent stages, and several gaps and limitations persist. This Review provides a comprehensive overview of the synthesis, properties, and applications of recent progress in EF-DCPNs. Firstly, synthetic routes to a rich variety of EF-DCPNs possessing two distinct types of dynamic bonds (i.e., imine, disulfide, ester, hydrogen bond, coordination bond, and other bonds) are introduced. Subsequently, complex structure- and dynamic nature-dependent mechanical, thermal, and electrical properties of EF-DCPNs are discussed, followed by their exemplary applications in electronics and biotechnology. Finally, future research directions in this rapidly evolving field are outlined.

Synergistically Modulating Conductive Filaments in Ion-Based Memristors for Enhanced Analog In-Memory Computing.

Memristors offer a promising solution to address the performance and energy challenges faced by conventional von Neumann computer systems. Yet, stochastic ion migration in conductive filament often leads to an undesired performance tradeoff between memory window, retention, and endurance. Herein, a robust memristor based on oxygen-rich SnO2 nanoflowers switching medium, enabled by seed-mediated wet chemistry, to overcome the ion migration issue for enhanced analog in-memory computing is reported. Notably, the interplay between the oxygen vacancy (Vo) and Ag ions (Ag+ ) in the Ag/SnO2 /p++ -Si memristor can efficiently modulate the formation and abruption of conductive filaments, thereby resulting in a high on/off ratio (>106), long memory retention (10-year extrapolation), and low switching variability (SV = 6.85%). Multiple synaptic functions, such as paired-pulse facilitation, long-term potentiation/depression, and spike-time dependent plasticity, are demonstrated. Finally, facilitated by the symmetric analog weight updating and multiple conductance states, a high image recognition accuracy of ≥ 91.39% is achieved, substantiating its feasibility for analog in-memory computing. This study highlights the significance of synergistically modulating conductive filaments in optimizing performance trade-offs, balancing memory window, retention, and endurance, which demonstrates techniques for regulating ion migration, rendering them a promising approach for enabling cutting-edge neuromorphic applications.

Strategies Toward High Selectivity, Activity, and Stability of Single-Atom Catalysts.

Single-atom catalysts (SACs) hold immense promise in facilitating the rational use of metal resources and achieving atomic economy due to their exceptional atom-utilization efficiency and distinct characteristics. Despite the growing interest in SACs, only limited reviews have holistically summarized their advancements centering on performance metrics. In this review, first, a thorough overview on the research progress in SACs is presented from a performance perspective and the strategies, advancements, and intriguing approaches employed to enhance the critical attributes in SACs are discussed. Subsequently, a comprehensive summary and critical analysis of the electrochemical applications of SACs are provided, with a particular focus on their efficacy in the oxygen reduction reaction , oxygen evolution reaction, hydrogen evolution reaction , CO2 reduction reaction, and N2 reduction reaction . Finally, the outline future research directions on SACs by concentrating on performance-driven investigation, where potential areas for improvement are identified and promising avenues for further study are highlighted, addressing challenges to unlock the full potential of SACs as high-performance catalysts.

Technology and Integration Roadmap for Optoelectronic Memristor.

Optoelectronic memristors (OMs) have emerged as a promising optoelectronic Neuromorphic computing paradigm, opening up new opportunities for neurosynaptic devices and optoelectronic systems. These OMs possess a range of desirable features including minimal crosstalk, high bandwidth, low power consumption, zero latency, and the ability to replicate crucial neurological functions such as vision and optical memory. By incorporating large-scale parallel synaptic structures, OMs are anticipated to greatly enhance high-performance and low-power in-memory computing, effectively overcoming the limitations of the von Neumann bottleneck. However, progress in this field necessitates a comprehensive understanding of suitable structures and techniques for integrating low-dimensional materials into optoelectronic integrated circuit platforms. This review aims to offer a comprehensive overview of the fundamental performance, mechanisms, design of structures, applications, and integration roadmap of optoelectronic synaptic memristors. By establishing connections between materials, multilayer optoelectronic memristor units, and monolithic optoelectronic integrated circuits, this review seeks to provide insights into emerging technologies and future prospects that are expected to drive innovation and widespread adoption in the near future.

Locally Ordered Single-Atom Catalysts for Electrocatalysis.

Single-atom catalysts manifest nearly 100 % atom utilization efficiency, well-defined active sites, and high selectivity. However, their practical applications are hindered by a low atom loading density, uncontrollable location, and ambiguous interaction with the support, thereby posing challenges to maximizing their electrocatalytic performance. To address these limitations, the ability to arrange randomly dispersed single atoms into locally ordered single-atom catalysts (LO-SACs) substantially influences the electronic effect between reactive sites and the support, the synergistic interaction among neighboring single atoms, the bonding energy of intermediates with reactive sites and the complexity of the mechanism. As such, it dramatically promotes reaction kinetics, reduces the energy barrier of the reaction, improves the performance of the catalyst and simplifies the reaction mechanism. In this review, firstly, we introduce a variety of compelling characteristics of LO-SACs as electrocatalysts. Subsequently, the synthetic strategies, characterization methods and applications of LO-SACs in electrocatalysis are discussed. Finally, the future opportunities and challenges are elaborated to encourage further exploration in this rapidly evolving field.

Ethylene Methoxycarbonylation over Heterogeneous Pt1/MoS2 Single-Atom Catalyst: Metal-Support Concerted Catalysis.

Ethylene methoxycarbonylation (EMC) to methyl propanoate (MP) is an industrially important reaction and commercially uses a homogeneous Pd-phosphine organometallic complex as the catalyst and corrosive strong acid as the promoter. In this work, we develop a Pt1/MoS2 heterogeneous single-atom catalyst (SAC) which exhibits high activity, selectivity, and good recyclability for EMC reaction without need of any liquid acid. The production rate of MP achieves 0.35 gMP gcat-1 h-1 with MP selectivity of 91.1% at 1 MPa CO, 1 MPa C2H4, and 160 °C, which can be doubled at 2 MPa CO and corresponds to 320.1 molMP molPt-1 h-1, at least 1 order of magnitude higher than the earlier reported heterogeneous catalyst and even comparable to some of homogeneous catalyst. Advanced characterizations and DFT calculations reveal that all the Pt single atoms are located at the Mo vacancies along the Mo edge of the MoS2 nanosheets, forming pocket-like Mo-S-Pt1-S-Mo ensembles with uniform and well-defined structure. Methanol is first adsorbed and dissociated on Mo sites, and the produced H spillovers to the adjacent Pt site forming Pt-H species which then activate ethylene, forming Pt-ethyl species. Meanwhile, CO adsorbed on the other Mo site reacts with the Pt-ethyl species, yielding propionyl species, and this carbonylation is the rate-determining step. The final methoxylation step proceeds via the nucleophilic attack of propionyl species by -OCH3 affording the final product MP. Such a metal-support concerted catalysis enabled by the Mo-S-Pt1-S-Mo multisite ensemble opens a new avenue for SACs to promote the multimolecular reactions that prevail in homogeneous catalysis.

Effects of microplastics on litter decomposition in wetland soil.

Microplastics (MPs) may interfere with the primary ecological processes of soil, which has become a growing global environmental issue. In terrestrial ecosystems, litter decomposition is the main process of nutrient cycling, particularly for carbon (C) and nitrogen (N). However, how microplastic pollution could alter wetland litter decomposition has barely been investigated. Therefore, a 100-day lab-scale litter decomposition experiment was conducted using Shengjin Lake wetland soil, which was treated with two types of MPs (polyethylene, PE and polyvinyl chloride, PVC) at three concentrations (0.1%, 0.5%, and 2.5%, w/w), to explore if and how MPs accumulation could affect wetland litter decomposition processes. According to our research, the PE and PVC greatly slowed the decomposition rate of wetland litter. Compared with control treatments, the addition of MPs decreased litter quality (high C:N), reduced litter decomposition-related soil enzyme activity, decreased the diversity of bacteria, and altered microbial community structure and potential functional gene abundance linked to litter decomposition. These findings revealed that MPs could affect the main process of C and N cycling in wetland ecosystems, providing important cues for further research on the wetland ecosystem function.

Al2 O3 -Stabilized Pt Nanozymes: Peroxidase Mimetics and Application in Glucose Detection.

As promising alternatives for natural enzymes, much attention has been paid to nanozymes. And our recent study showed that the medium acid sites on the support are the active sites for the adsorption and oxidation of the substrate. Thus, in this work, due to the abundance of medium acid sites, Al2 O3 was chosen as the support to prepare Pt/Al2 O3 nanozymes. Through the Pt/Al2 O3 samples, we further proved that the distribution of the Pt clusters and the amount of the medium acid sites can significantly influence the peroxidase-like activity. Then the Pt/Al2 O3 sample was used for the detection of glucose. And as low as 0.96 µM glucose could be detected with a linear range from 5-60 µM via our method. This work showed the great potential applications of the easily prepared Pt/Al2 O3 samples in varieties of simple, robust, and easy-to-make analytical approaches in the future.

Atomic Insights into Synergistic Nitroarene Hydrogenation over Nanodiamond-Supported Pt1 -Fe1 Dual-Single-Atom Catalyst.

Fundamental understanding of the synergistic effect of bimetallic catalysts is of extreme significance in heterogeneous catalysis, but a great challenge lies in the precise construction of uniform dual-metal sites. Here, we develop a novel method for constructing Pt1 -Fe1 /ND dual-single-atom catalyst, by anchoring Pt single atoms on Fe1 -N4 sites decorating a nanodiamond (ND) surface. Using this catalyst, the synergy of nitroarenes selective hydrogenation is revealed. In detail, hydrogen is activated on the Pt1 -Fe1 dual site and the nitro group is strongly adsorbed on the Fe1 site via a vertical configuration for subsequent hydrogenation. Such synergistic effect decreases the activation energy and results in an unprecedented catalytic performance (3.1 s-1 turnover frequency, ca. 100 % selectivity, 24 types of substrates). Our findings advance the applications of dual-single-atom catalysts in selective hydrogenations and open up a new way to explore the nature of synergistic catalysis at the atomic level.

Biomimetic Synthesis of Organic Molecular-Doped Fluorescent Guanine Crystals with Pearlescence.

Biomimetic synthesis of guanine crystals has been focused on in the last years. However, multi-functional guanine crystals occluded with fluorescent molecules have not been realized in the laboratory. Here, the controllable synthesis of guanine crystal microplatelets with fluorescence and pearlescence was achieved for the first time by incorporating Nile red (NR) or fluorescein isothiocyanate (FITC) molecules into guanine crystals. The synthesized fluorescent guanine crystals are pure ß-phase anhydrous guanine single crystals. Aqueous suspensions with NR- and FITC-doped guanine crystals exhibit distinct pearlescence. The fluorescence intensities of NR and FITC were greatly enhanced after being doped into guanine crystals due to the inhibition of aggregation-caused quenching. Moreover, films composed of fluorescent guanine microplatelets exhibit high diffuse reflection intensity (70 %). This work provides a strategy to synthesize multifunctional materials composed of organic crystals occluded with dyes.

A Manganese-Based Metal-Organic Framework as a Cold-Adapted Nanozyme.

The development of cold-adapted enzymes with high efficiency and good stability is an advanced strategy to overcome the limitations of catalytic medicine in low and cryogenic temperatures. In this work, inspired by natural enzymes, a novel cold-adapted nanozyme based on a manganese-based nanosized metal-organic framework (nMnBTC) is designed and synthesized. The nMnBTC as an oxidase mimetic not only exhibits excellent activity at 0 °C, but also presents almost no observable activity loss as the temperature is increased to 45 °C. This breaks the traditional recognition that enzymes show maximum activity only under specific psychrophilic or thermophilic condition. The superior performance of nMnBTC as a cold-adapted nanozyme can be attributed to its high-catalytic efficiency at low temperature, good substrate affinity, and flexible conformation. Based on the robust performance of nMnBTC, a low-temperature antiviral strategy is developed to inactivate influenza virus H1N1 even at -20 °C. These results not only provide an important guide for the rational design of highly efficient artificial cold-adapted enzymes, but also pave a novel way for biomedical application in cryogenic fields.

Structural Insights into the Phosphorylation-Enhanced Deubiquitinating Activity of UCHL3 and Ubiquitin Chain Cleavage Preference Analysis.

Ubiquitin C-terminal hydrolase-L3 (UCHL3), an important member of the ubiquitin C-terminal hydrolase family, is involved in DNA repair and cancer development. UCHL3 can cleave only complexes of monoubiquitin and its conjugates, such as Ub-AMC, His, or small ubiquitin-like modifier, but not polyubiquitin chains. Phosphorylation of Ser75 promotes the cleavage activity of UCHL3 toward poly-ubiquitin chains in vivo, but biochemical evidence in vitro is still lacking. Here, we first analyzed the structure of simulated phosphorylated UCHL3S75E and the complex of UCHL3S75E with Ub-PA and preliminarily explained the structural mechanism of phosphorylation-enhanced UCHL3 deubiquitinating activity. Additionally, the cleavage activity of UCHL3 toward different types of synthesized poly-ubiquitin chains in vitro was tested. The results showed that purified UCHL3S75E enhanced the cleavage activity toward Ub-AMC compared to UCHL3WT. Meanwhile, UCHL3S75E and UCHL3WT did not show any cleavage activity for different types of di-ubiquitin and tri-ubiquitin chains. However, UCHL3 could hydrolyze the K48 tetra-ubiquitin chain, providing compelling in vitro evidence confirming previous in vivo results. Thus, this study shows that UCHL3 can hydrolyze and has a cleavage preference for polyubiquitin chains, which expands our understanding of the phosphorylation regulation of UCHL3 and lays a foundation for further elucidation of its physiological role.

Highly Selective Hydrogenation of CO2 to Ethanol via Designed Bifunctional Ir1-In2O3 Single-Atom Catalyst.

Recently, CO2 hydrogenation for the controlled growth of the carbon chain to produce high-value C2 or C2+ products has attracted great interest, where achieving high selectivity for a specific product remains a challenge, especially for ethanol. Herein, we have designed a bifunctional Ir1-In2O3 single-atom catalyst, integrating two active catalytic centers by anchoring the monatomic Ir onto the In2O3 carrier. This Ir1-In2O3 single-atom catalyst is efficient for the hydrogenation of CO2 in liquid, yielding a high selectivity for ethanol (>99%) with an excellent initial turnover frequency (481 h-1). Characterization shows that the isolated Ir atom couples with the adjacent oxygen vacancy forming a Lewis acid-base pair, which activates the CO2 and forms the intermediate species of carbonyl (CO*) adsorbed on the Ir atom. Coupling this CO* with the methoxide adsorbed on the In2O3 forms a C-C bond. The strategy of this effective bifunctional single-atom catalyst by synergistically utilizing the distinct catalytic roles of the single-atom site and the substrates provides a new avenue in catalyst design for complex catalysis.

Structural Regulation of Magnetic Polymer Microsphere@Ionic Liquids with an Intermediate Protective Layer and Application as Core-Shell-Shell Catalysts with High Stability and Activity.

A novel ionic liquid immobilized on a magnetic polymer microsphere catalyst is reported in this paper. The obtained core-shell-shell catalyst consisted of magnetic nanoparticles (MNPs) as the core, catalytic inert St-co-DVB as the intermediate protective layer, and cross-linked polyaryl imidazole ionic liquids as the active catalytic layer located at the outermost [Im[OH]/MNPs@P(St-DVB)@P(VBC-DVB)]. This catalyst exhibited a high ion-exchange rate (64.65%), high saturation magnetic strength, and excellent acid and alkali corrosion resistance. In the catalyzed Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate, the conversion of benzaldehyde maintained at 92.1% during six times reuse. Optimizing the materials of the protective layer and regulating the thickness of the inert protective layer decreased the corrosion ratio of MNPs in acidic media from 44.82 to 0.44%. Adjusting the thickness of the catalytic layer realized excellent catalytic activity (97%) and high magnetic response performance. In summary, introducing an inert protective layer to the structure of ionic liquids immobilized on the magnetic polymer microsphere catalyst, regulating its thickness, and optimizing its structure achieved a catalyst with high activity, excellent stability, and easy magnetic separation.

High-Density and Thermally Stable Palladium Single-Atom Catalysts for Chemoselective Hydrogenations.

Single-atom catalysts (SACs) have shown superior activity and/or selectivity for many energy- and environment-related reactions, but their stability at high site density and under reducing atmosphere remains unresolved. Herein, we elucidate the intrinsic driving force of a Pd single atom with high site density (up to 5 wt %) under reducing atmosphere, and its unique catalytic performance for hydrogenation reactions. In situ experiments and calculations reveal that Pd atoms tend to migrate into the surface vacancy-enriched MoC surface during the carburization process by transferring oxide crystals to carbide crystals, leading to the surface enrichment of atomic Pd instead of formation of particles. The Pd1 /α-MoC catalyst exhibits high activity and excellent selectivity for liquid-phase hydrogenation of substituted nitroaromatics (>99 %) and gas-phase hydrogenation of CO2 to CO (>98 %). The Pd1 /α-MoC catalyst could endure up to 400 °C without any observable aggregation of single atoms.

Controlling CO2 Hydrogenation Selectivity by Metal-Supported Electron Transfer.

Tuning CO2 hydrogenation selectivity to obtain targeted value-added chemicals and fuels has attracted increasing attention. However, a fundamental understanding of the way to control the selectivity is still lacking, posing a challenge in catalyst design and development. Herein, we report our new discovery in ambient pressure CO2 hydrogenation reaction where selectivity can be completely reversed by simply changing the crystal phases of TiO2 support (anatase- or rutile-TiO2 ) or changing metal loadings on anatase-TiO2 . Operando spectroscopy and NAP-XPS studies reveal that the determining factor is a different electron transfer from metal to the support, most probably as a result of the different extents of hydrogen spillover, which changes the adsorption and activation of the intermediate of CO. Based on this new finding, we can not only regulate CO2 hydrogenation selectivity but also tune catalytic performance in other important reactions, thus opening up a door for efficient catalyst development by rational design.

Strong Metal-Support Interactions between Pt Single Atoms and TiO2.

Strong metal-support interaction (SMSI) has gained great attention in the field of heterogeneous catalysis. However, whether single-atom catalysts can exhibit SMSI remains unknown. Here, we demonstrate that SMSI can occur on TiO2 -supported Pt single atoms but at a much higher reduction temperature than that for Pt nanoparticles (NPs). Pt single atoms involved in SMSI are not covered by the TiO2 support nor do they sink into its subsurface. The suppression of CO adsorption on Pt single atoms stems from coordination saturation (18-electron rule) rather than the physical coverage of Pt atoms by the support. Based on the new finding it is revealed that single atoms are the true active sites in the hydrogenation of 3-nitrostyrene, while Pt NPs barely contribute to the activity since the NP sites are selectively encapsulated. The findings in this work provide a new approach to study the active sites by tuning SMSI.

Photo-thermo Catalytic Oxidation over a TiO2 -WO3 -Supported Platinum Catalyst.

Photo-thermo catalysis, which integrates photocatalysis on semiconductors with thermocatalysis on supported nonplasmonic metals, has emerged as an attractive approach to improve catalytic performance. However, an understanding of the mechanisms in operation is missing from both the thermo- and photocatalytic perspectives. Deep insights into photo-thermo catalysis are achieved via the catalytic oxidation of propane (C3 H8 ) over a Pt/TiO2 -WO3 catalyst that severely suffers from oxygen poisoning at high O2 /C3 H8 ratios. After introducing UV/Vis light, the reaction temperature required to achieve 70 % conversion of C3 H8 lowers to a record-breaking 90 °C from 324 °C and the apparent activation energy drops from 130 kJ mol-1 to 11 kJ mol-1 . Furthermore, the reaction order of O2 is -1.4 in dark but reverses to 0.1 under light, thereby suppressing oxygen poisoning of the Pt catalyst. An underlying mechanism is proposed based on direct evidence of the in-situ-captured reaction intermediates.

Strong metal-support interaction promoted scalable production of thermally stable single-atom catalysts.

Single-atom catalysts (SACs) have demonstrated superior catalytic performance in numerous heterogeneous reactions. However, producing thermally stable SACs, especially in a simple and scalable way, remains a formidable challenge. Here, we report the synthesis of Ru SACs from commercial RuO2 powders by physical mixing of sub-micron RuO2 aggregates with a MgAl1.2Fe0.8O4 spinel. Atomically dispersed Ru is confirmed by aberration-corrected scanning transmission electron microscopy and X-ray absorption spectroscopy. Detailed studies reveal that the dispersion process does not arise from a gas atom trapping mechanism, but rather from anti-Ostwald ripening promoted by a strong covalent metal-support interaction. This synthetic strategy is simple and amenable to the large-scale manufacture of thermally stable SACs for industrial applications.

One-Pot Conversion of Lignin into Naphthenes Catalyzed by a Heterogeneous Rhenium Oxide-Modified Iridium Compound.

The direct transformation of lignin into fuels and chemicals remains a huge challenge because of the recalcitrant and complicated structure of lignin. In this study, rhenium oxide-modified iridium supported on SiO2 (Ir-ReOx /SiO2 ) is employed for the one-pot conversion of various lignin model compounds and lignin feedstocks into naphthenes. Up to 100 % yield of cyclohexane from model compounds and 44.3 % yield of naphthenes from lignin feedstocks are achieved. 2 D HSQC NMR spectroscopy before and after the reaction confirms the activity of Ir-ReOx /SiO2 in the cleavage of the C-O bonds and hydrodeoxygenation of the depolymerized products. H2 temperature-programmed reduction, temperature-programmed desorption of NH3 , IR spectroscopy of pyridine adsorption, X-ray photoelectron spectroscopy, X-ray absorption fine structure analysis, and control experiments reveal that a synergistic effect between Ir and ReOx in Ir-ReOx /SiO2 plays a crucial role in the high performance; ReOx is mainly responsible for the cleavage of C-O bonds, whereas Ir is responsible for hydrodeoxygenation and saturation of the benzene rings. This methodology opens up an energy-efficient route for the direct conversion of lignin into valuable naphthenes.