A Structural Mimic of Carbonic Anhydrase in Zeolitic Imidazolate Frameworks via Trans-functionalization for Enhancing Hydrolytic Activity.

Metal-organic frameworks (MOFs) have been widely considered as ideal platforms for the preparation of biomimetic catalysts, but it remains challenging to fabricate MOF-based enzyme-like catalysts with optimal activity. Here, we leverage the inherent flexibility of MOFs and propose a novel trans-functionalization strategy to construct a carbonic anhydrase (CA) mimic by the structural transformation from ZIF-L to ZIF-8. Theoretical and experimental results reveal that during the structural transformation, the hydroxyl group will preferentially coordinate with the interlayer Zn clusters to form the CA-like active center Zn-N3-OH. Therefore, more accessible active centers are generated on the as-prepared ZIF-8-OH, resulting in substantially enhanced catalytic activity in the hydrolysis of para-nitrophenyl acetate.

Wedging crystals to fabricate crystalline framework nanosheets via mechanochemistry.

Mechanochemistry studies the effect of mechanical force on chemical bonds, bringing opportunities for synthesizing alloys, ceramics, organics, polymers, and biomaterials. A vital issue of applying macro-scale mechanical force to manipulate crystal structures is finding ways to precisely adjust the force directions to break micro-scale target chemical bonds. Inspired by a common technique of driving a wedge into the wood to make wood chopping much easier, a wedging strategy of splitting three-dimensional structured crystalline frameworks and then converting them to nanosheets was proposed, where specific molecules were wedged into crystalline frameworks to drive the directional transmission of mechanical force to break chemical bonds. As a result, various crystalline framework nanosheets including metal-organic framework nanosheets, covalent organic framework nanosheets, and coordination polymer nanosheets were fabricated. This wedging crystal strategy exhibits advantages of operability, flexibility and designability, and furthermore, it is expected to expand mechanochemistry applications in material preparation.

Design of AI-Enhanced and Hardware-Supported Multimodal E-Skin for Environmental Object Recognition and Wireless Toxic Gas Alarm.

Post-earthquake rescue missions are full of challenges due to the unstable structure of ruins and successive aftershocks. Most of the current rescue robots lack the ability to interact with environments, leading to low rescue efficiency. The multimodal electronic skin (e-skin) proposed not only reproduces the pressure, temperature, and humidity sensing capabilities of natural skin but also develops sensing functions beyond it-perceiving object proximity and NO2 gas. Its multilayer stacked structure based on Ecoflex and organohydrogel endows the e-skin with mechanical properties similar to natural skin. Rescue robots integrated with multimodal e-skin and artificial intelligence (AI) algorithms show strong environmental perception capabilities and can accurately distinguish objects and identify human limbs through grasping, laying the foundation for automated post-earthquake rescue. Besides, the combination of e-skin and NO2 wireless alarm circuits allows robots to sense toxic gases in the environment in real time, thereby adopting appropriate measures to protect trapped people from the toxic environment. Multimodal e-skin powered by AI algorithms and hardware circuits exhibits powerful environmental perception and information processing capabilities, which, as an interface for interaction with the physical world, dramatically expands intelligent robots' application scenarios.

Boron-Doped Dinickel Phosphide to Enhance Polysulfide Conversion and Suppress Shuttling in Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are promising for next-generation high-energy energy storage systems. However, the slow reaction kinetics render mobile polysulfides hardly controlled, yielding shuttling effects and eventually damaging Li metal anodes. To improve the cyclability of Li-S batteries, high-efficiency catalysts are desired to accelerate polysulfide conversion and suppress the shuttling effect. Herein, we studied a doping system with Ni2P and Ni2B as the end members and found a B-doped Ni2P catalyst that demonstrates high activity for Li-S batteries. As anionic dopants, B demonstrates an interesting reverse electron transfer to P and tunes the electronic structure of Ni2P dramatically. The resultant B-doped Ni2P exhibits short Ni-B bonds and strong Ni-S interaction, and the electron donation of B to P further enhances the adsorption of polysulfide on catalysts. The S-S bonds of polysulfides were activated appropriately, therefore decreasing a low energy barrier for conversion reactions.

In Situ Structural Densification of Hydrogel Network and Its Interface with Electrodes for High-Performance Multimodal Artificial Skin.

The multisensory responsiveness of hydrogels positions them as promising candidates for artificial skin, whereas the mismatch of modulus between soft hydrogels and hard electrodes as well as the poor adhesion and conductance at the interface greatly impairs the stability of electronics devices. Herein, we propose an in situ postprocessing approach utilizing electrochemical reactions between metals (Zn, etc.) and hydrogels to synergistically achieve strong adhesion of the hydrogel-electrode interface, low interfacial impedance, and local strain isolation due to the structural densification of the hydrogel network. The mechanism is that Zn electrochemically oxidizes to Zn2+ and injects into the hydrogel, gradually forming a mechanically interlocked structure, Zn2+-polymer dual-helix structural nodes, and a high-modulus ZnO from the surface to the interior. Compared to untreated samples, the treated sample displays 8.7 times increased interfacial adhesion energy between the hydrogel and electrode (87 J/m2), 95% decreased interfacial impedance (218.8 Ω), and a high-strain isolation efficiency (εtotal/εisolation > 400). Akin to human skin, the prepared sensor demonstrates multimodal sensing capabilities, encompassing highly sensitive strain perception and simultaneous perception of temperature, humidity, and oxygen content unaffected by strain interference. This easy on-chip preparation of hydrogel-based multimodal sensor array shows great potential for health and environment monitoring as artificial skin.

Achieving High Ionic Conductivity and Mechanical Strength by a Leather Gel Electrolyte for Flexible Zinc-Ion Batteries.

The continuous advancement in the field of flexible and wearable electronics has led to increased research interest in safe, low-cost, and flexible zinc-ion batteries, particularly with a focus on flexible electrolytes. In this study, we present a leather gel electrolyte (LGE) that offers robust mechanical properties and an excellent electrochemical performance. LGE exhibits an ionic conductivity of 1.36 × 10-2 S cm-1 and achieves a capacity of 303.7 mAh g-1 in flexible zinc-manganese dioxide batteries. Even after 1000 cycles, the capacity retention remains above 90%, demonstrating outstanding performance in protecting the zinc anode. Furthermore, such a flexible battery shows good resistance to damage due to the strong mechanical strength originating from leather. Notably, LGE utilizes green and sustainable leather as a raw material, making it a promising option for sustainable flexible devices.

Prussian blue analogue derived from leather waste as a bifunctional catalyst in zinc-air batteries.

A Prussian blue analogue was synthesized using biomass leather waste as a precursor by doping with Co2+ ions. This material, demonstrates good performance in both the oxygen reduction reaction and oxygen evolution reaction, and exhibits excellent charge-discharge performance and stability in zinc-air batteries.

Polysarcosine as PEG Alternative for Enhanced Camptothecin-Induced Cancer Immunogenic Cell Death.

Nanomedicine-enhanced immunogenic cell death (ICD) has attracted considerable attention for its great potential in cancer treatment. Even though polyethylene glycol (PEG) is widely recognized as the gold standard for surface modification of nanomedicines, some shortcomings associated with this PEGylation, such as hindered cell endocytosis and accelerated blood clearance phenomenon, have been revealed in recent years. Notably, polysarcosine (PSar) as a highly biocompatible polymer can be finely synthesized by mild ring-opening polymerization (ROP) of sarcosine N-carboxyanhydrides (Sar-NCAs) and exhibit great potential as an alternative to PEG. In this article, PSar-b-polycamptothecin block copolymers are synthesized by sequential ROP of camptothecin-based NCAs (CPT-NCAs) and Sar-NCAs. Then, the detailed and systematic comparison between PEGylation and PSarylation against the 4T1 tumor model indicates that PSar decoration can facilitate the cell endocytosis, greatly enhancing the ICD effects and antitumor efficacy. Therefore, it is believed that this well-developed PSarylation technique will achieve effective and precise cancer treatment in the near future.

Abnormal thermally-stimulated dynamic organic phosphorescence.

Dynamic luminescence behavior by external stimuli, such as light, thermal field, electricity, mechanical force, etc., endows the materials with great promise in optoelectronic applications. Upon thermal stimulus, the emission is inevitably quenched due to intensive non-radiative transition, especially for phosphorescence at high temperature. Herein, we report an abnormal thermally-stimulated phosphorescence behavior in a series of organic phosphors. As temperature changes from 198 to 343 K, the phosphorescence at around 479 nm gradually enhances for the model phosphor, of which the phosphorescent colors are tuned from yellow to cyan-blue. Furthermore, we demonstrate the potential applications of such dynamic emission for smart dyes and colorful afterglow displays. Our results would initiate the exploration of dynamic high-temperature phosphorescence for applications in smart optoelectronics. This finding not only contributes to an in-depth understanding of the thermally-stimulated phosphorescence, but also paves the way toward the development of smart materials for applications in optoelectronics.

Exfoliation of Metal-Organic Frameworks to Give 2D MOF Nanosheets for the Electrocatalytic Oxygen Evolution Reaction.

The structure and properties of materials are determined by a diverse range of chemical bond formation and breaking mechanisms, which greatly motivates the development of selectively controlling the chemical bonds in order to achieve materials with specific characteristics. Here, an orientational intervening bond-breaking strategy is demonstrated for synthesizing ultrathin metal-organic framework (MOF) nanosheets through balancing the process of thermal decomposition and liquid nitrogen exfoliation. In such approach, proper thermal treatment can weaken the interlayer bond while maintaining the stability of the intralayer bond in the layered MOFs. And the following liquid nitrogen treatment results in significant deformation and stress in the layered MOFs' structure due to the instant temperature drop and drastic expansion of liquid N2, leading to the curling, detachment, and separation of the MOF layers. The produced MOF nanosheets with five cycles of treatment are primarily composed of nanosheets that are less than 10 nm in thickness. The MOF nanosheets exhibit enhanced catalytic performance in oxygen evolution reactions owing to the ultrathin thickness without capping agents which provide improved charge transfer efficiency and dense exposed active sites. This strategy underscores the significance of orientational intervention in chemical bonds to engineer innovative materials.

Synthesis of Pd/Carbon Hollow Spheres by the Microwave Discharge Method for Catalytic Debenzylation.

Pd/C catalysts have been widely applied in the debenzylation process due to their excellent ability of hydrogenolysis. However, they have been suffering from the problems of agglomeration and loss of active components, which lead to decreased and unstable activity. Thus, it is still a challenge to achieve Pd/C catalysts with high activity and stability. Herein, we propose a strategy for preparing Pd/C catalysts on porous carbon hollow spheres by a microwave discharge method. Due to the high-temperature property and reducibility of microwave discharge, Pd precursors can be rapidly reduced, resulting in well-dispersed Pd nanoparticles with a small size on the carbon carrier. Besides, the matched mesopores in the carbon hollow spheres can anchor Pd nanoparticles and effectively reduce the agglomeration and loss of Pd nanoparticles during the catalytic reaction. As a result, the as-prepared Pd/mesoporous carbon hollow spheres exhibit high and stable activity in the debenzylation reaction.

Water-assisted hydrogen spillover in Pt nanoparticle-based metal-organic framework composites.

Hydrogen spillover is the migration of activated hydrogen atoms from a metal particle onto the surface of catalyst support, which has made significant progress in heterogeneous catalysis. The phenomenon has been well researched on oxide supports, yet its occurrence, detection method and mechanism on non-oxide supports such as metal-organic frameworks (MOFs) remain controversial. Herein, we develop a facile strategy for efficiency enhancement of hydrogen spillover on various MOFs with the aid of water molecules. By encapsulating platinum (Pt) nanoparticles in MOF-801 for activating hydrogen and hydrogenation of C=C in the MOF ligand as activated hydrogen detector, a research platform is built with Pt@MOF-801 to measure the hydrogenation region for quantifying the efficiency and spatial extent of hydrogen spillover. A water-assisted hydrogen spillover path is found with lower migration energy barrier than the traditional spillover path via ligand. The synergy of the two paths explains a significant boost of hydrogen spillover in MOF-801 from imperceptible existence to spanning at least 100-nm-diameter region. Moreover, such strategy shows universality in different MOF and covalent organic framework materials for efficiency promotion of hydrogen spillover and improvement of catalytic activity and antitoxicity, opening up new horizons for catalyst design in porous crystalline materials.

Opportunities and Challenges of Metal-Organic Framework Micro/Nano Reactors for Cascade Reactions.

Building bridges among different types of catalysts to construct cascades is a highly worthwhile pursuit, such as chemo-, bio-, and chemo-bio cascade reactions. Cascade reactions can improve the reaction efficiency and selectivity while reducing steps of separation and purification, thereby promoting the development of "green chemistry". However, compatibility issues in cascade reactions pose significant constraints on the development of this field, particularly concerning the compatibility of diverse catalyst types, reaction conditions, and reaction rates. Metal-organic framework micro/nano reactors (MOF-MNRs) are porous crystalline materials formed by the self-assembly coordination of metal sites and organic ligands, possessing a periodic network structure. Due to the uniform pore size with the capability of controlling selective transfer of substances as well as protecting active substances and the organic-inorganic parts providing reactive microenvironment, MOF-MNRs have attracted significant attention in cascade reactions in recent years. In this Perspective, we first discuss how to address compatibility issues in cascade reactions using MOF-MNRs, including structural design and synthetic strategies. Then we summarize the research progress on MOF-MNRs in various cascade reactions. Finally, we analyze the challenges facing MOF-MNRs and potential breakthrough directions and opportunities for the future.

Vanadium Intercalation into Niobium Disulfide to Enhance the Catalytic Activity for Lithium-Sulfur Batteries.

Despite their high specific energy and great promise for next-generation energy storage, lithium-sulfur (Li-S) batteries suffer from polysulfide shuttling, slow redox kinetics, and poor cyclability. Catalysts are needed to accelerate polysulfide conversion and suppress the shuttling effect. However, a lack of structure-activity relationships hinders the rational development of efficient catalysts. Herein, we studied the Nb-V-S system and proposed a V-intercalated NbS2 (Nb3VS6) catalyst for high-efficiency Li-S batteries. Structural analysis and modeling revealed that undercoordinated sulfur anions of [VS6] octahedra on the surface of Nb3VS6 may break the catalytic inertness of the basal planes, which are usually the primary exposed surfaces of many 2D layered disulfides. Using Nb3VS6 as the catalyst, the resultant Li-S batteries delivered high capacities of 1541 mAh g-1 at 0.1 C and 1037 mAh g-1 at 2 C and could retain 73.2% of the initial capacity after 1000 cycles. Such an intercalation-induced high activity offers an alternative approach to building better Li-S catalysts.

New Function of Metal-Organic Framework: Structurally Ordered Metal Promoter.

The remarkable roles of metal promoters have been known for nearly a century, but it is still a challenge to find a suitable structure model to reveal the action mechanism behind metal promoters. Herein, a new function of metal-organic frameworks (MOFs) is developed as an ideal model to construct structurally ordered metal promoters by a targeted post-modification strategy. MOFs as model not only favor clearing the real action mechanism behind metal promoters, but also can anchor one or multiple kinds of metal promoters especially noble metal promoters. Typically, the as-prepared Pd/bpy-UiO-Cu catalysts show high selectivity (>99%) toward 4-nitrophenylethane in 4-nitrostyrene hydrogenation, mainly due to the enhanced interaction between Pd nanoparticles and MOF carriers induced by Cu promoters, thus inhibiting the hydrogenation of 4-nitrophenylethane. This strategy with flexibility and universality will open up a new route to synthesize efficient catalysts with structurally ordered metal promoters.

Polymerization-Induced Self-Assembly for Efficient Fabrication of Biomedical Nanoplatforms.

Amphiphilic copolymers can self-assemble into nano-objects in aqueous solution. However, the self-assembly process is usually performed in a diluted solution (<1 wt%), which greatly limits scale-up production and further biomedical applications. With recent development of controlled polymerization techniques, polymerization-induced self-assembly (PISA) has emerged as an efficient approach for facile fabrication of nano-sized structures with a high concentration as high as 50 wt%. In this review, after the introduction, various polymerization method-mediated PISAs that include nitroxide-mediated polymerization-mediated PISA (NMP-PISA), reversible addition-fragmentation chain transfer polymerization-mediated PISA (RAFT-PISA), atom transfer radical polymerization-mediated PISA (ATRP-PISA), and ring-opening polymerization-mediated PISA (ROP-PISA) are discussed carefully. Afterward, recent biomedical applications of PISA are illustrated from the following aspects, i.e., bioimaging, disease treatment, biocatalysis, and antimicrobial. In the end, current achievements and future perspectives of PISA are given. It is envisioned that PISA strategy can bring great chance for future design and construction of functional nano-vehicles.

Technology Roadmap for Flexible Sensors.

Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.

Noncrystalline Carbon Anodes for Advanced Sodium-Ion Storage.

Developing an anode with excellent rate performance, long-cycle stability, high coulombic efficiency, and high specific capacity is one of the key research directions of sodium-ion batteries. Among all the anode materials, noncrystalline carbon (NCC) has great possibilities according to its supreme performance and low cost, but with the complexity and variability of the structure. With the in-depth study of the sodium storage behaviors of NCC in recent years, three modes of interlayer intercalation, clustering into micropores, and adsorption are reported and summarized. Although the storage mechanism has gradually become more evident, the complex behavior of the ions at different voltage regions, especially in the low-voltage (plateau) region, still remains controversial. It is essential to understand further the relationship between ions and NCC structure during energy storage processes. Based on the summary of previous works, this article has reviewed the storage mechanism of sodium ions in NCC and evaluated the structure-behavior relationship between sodium-ion storage and the carbon structure.

Construction of Metal-Organic Framework Films via Crosslinking-Induced Assembly.

The construction of metal-organic framework (MOF) films is a crucial step for integrating them into technical applications. However, due to the crystallization nature, it is difficult to grow most MOFs spontaneously or process them into films. Here, a convenient strategy is demonstrated for constructing MOF films by using modulators to achieve homogeneous assembly of MOF clusters. Small clusters in the early growth steps of MOFs can be stabilized by modulators to form fluidic precursors with good processibility. Then, simple removal of modulators will trigger the crosslinking of MOF clusters and lead to the formation of continuous films. This strategy is universal for the fabrication of several types of MOF films with large scale and controllable thickness, which can be deposited on a variety of substrates as well as can be patterned in micro/nano resolution. Additionally, versatile composite MOF films can be easily synthesized by introducing functional materials during the crosslinking process, which brings them broader application prospects.

Recent Progress in Surface and Interface Engineering for Electrocatalytic CO2 Reduction.

The conversion of CO2 through CO2 reduction reaction (CO2 RR) into valuable products has potential to lessen the greenhouse effect caused by uncontrolled CO2 emissions. Challenges of CO2 RR reaction lie in the stabilization of the reaction intermediate and the activation of the inert chemical bond of CO2 , but the application of CO2 RR at large scale is limited by the high cost and structural instability of traditional catalysts. By applying CO2 RR catalyst with delicate structure of stable CO2 intermediate to industrial production, the problems such as high cost of CO2 conversion, low catalytic selectivity and poor catalytic efficiency can be effectively solved, showing better application value and significance than traditional catalysts. This review focuses on the defects, and metal-support interaction (MSI) effect to modify the catalyst and other strategies to enhance the effectiveness of CO2 reduction. The challenges and prospects from the three perspectives are also discussed to provide suggestions for the designing of efficient CO2 RR catalysts in the future. This review offers new insights and research perspectives of reducing CO2 emission through recycling CO2 , and neutralizing the carbon cycle.