Soft bioelectronics require conductive hydrogels with balanced mechanical-electrical performance for high-fidelity electrophysiological recording, yet conventional ones lack a balance between stretchability and electrochemical stability due to poor interfacial charge transfer. We present a molecularly engineered polyoxometalate-functionalized mesoporous metal-organic framework (meso-MOF@POM) nanoarchitecture that simultaneously reinforces the hydrogel network and enhances interfacial charge kinetics. The meso-MOF serves as a hierarchical scaffold with multiscale channels for polymer anchoring, while the sub-nanometer Keggin-type POM layer creates abundant redox-mediated electron transfer pathways. Upon integration of meso-MOF@POM into a dual-network poly(acrylic acid)/polyacrylamide hydrogel, the composite hydrogel enables high stretchability (>1000% strain), minimal electrical creep (<0.13% s-1@100% strain), and good cyclic durability (>3000 cycles). Crucially, the engineered organic-inorganic interface endows the hydrogel with excellent pseudocapacitive charge-transfer kinetics, which achieves low skin-electrode impedance (64 kΩ at 1 Hz vs. 287 kΩ at 1 Hz for Ag/AgCl gel). As a result, the skin-interfacing electrode enables high-fidelity recording of on-skin electrophysiological signals, including electrocardiogram, electromyogram, and electrooculogram, with an enhanced signal-to-noise ratio (e.g., 23.8 dB for ECG vs. 21.3 dB for Ag/AgCl gel). This work provides a novel fabrication strategy for highly conductive interfaces, enabling long-term applications in wearable health monitors and human-machine interfaces.

The oxygen evolution reaction (OER) suffers from sluggish kinetics, necessitating efficient electrocatalysts to reduce overpotentials in water splitting. Currently recognized OER mechanisms primarily include the adsorbate evolution mechanism (AEM), lattice oxygen mechanism (LOM), and oxide path mechanism (OPM). Compared to AEM, limited by scaling relationships, and LOM, constrained by stability issues, the OPM offers a promising alternative by enabling direct O–O bond formation via dual active sites, thus bypassing *OOH intermediates and lattice O involvement and achieving a balance between activity and durability. However, activating the OPM process requires precise control over the spatial and electronic structure of active sites, making the design of OPM-based catalysts challenging. While previous reviews have focused on homo/heteronuclear diatomic perspectives of OPM-based catalysts, it is urgent to systematically summarize design strategies to provide a rational reference for their development. Herein, a review of design strategies for OPM-based OER catalysts across three scales is comprehensively presented, including in-situ engineering, doping-enabled sites reconstruction, and introducing new sites for nanoparticles, direct synthesis or post-treatments for molecular catalysts, and doping or template strategies for atom pairs or arrays. The unique advantage of atom arrays is also highlighted, and their future research directions and possible strategies are discussed. This review provides a systematic summary and forward-looking perspectives for rationally designing high-performance OPM-based OER catalysts.

To explore the effects of polyoxometalates modification on layered double hydroxides (LDHs) and metal-organic frameworks (MOFs), we prepared the H5PW10V2O40-modified CoFe-LDH and CoFe-MOF composites via solvothermal method. Notably, the MOF/POM composite achieves a lower overpotential of 340 mV at 1 A & centerdot;cm-2 in alkaline media and more excellent stability of a voltage of 1.90 V at 1 A & centerdot;cm-2 for over 800 h in the anion exchange membrane water electrolyzer than the LDH/POM, benefiting from stronger electronic interaction, and the lower potential for active-phase formation indicates faster catalytic activation. This work compares the effects of polyoxometalates on LDHs and MOFs, clarifying their differences.

Utilizing sustainable solar energy to address freshwater and energy shortages is a promising strategy. Here, we developed a multifunctional polyacrylamide (PAM)/reduced graphene oxide (rGO)@CuS (PG@CuSx) hydrogel. Effective light absorption and water transport of PG@CuSx was achieved by the multiple synergies of hydrophilic PAM, broad spectral absorption of rGO, narrow bandgap CuS, and porous microchannel structure. The surface warming characteristics of PG@CuS2.5 under sunlight was consistent with Fluent simulations, with evaporation rates up to 8.1 kg m-2 h- 1 (one sun) and 28.7 kg m-2 h- 1 (3 cm height). PG@CuS2.5 showed excellent salt tolerance (16 h without salt crystallization) and photocatalytic performance (90 % degradation of methylene blue). When integrated with a thermoelectric generator, the system simultaneously obtained an output voltage of 161.5 mV. This study provides a new strategy for the development of a multifunctional hydro-energy cogeneration system with high efficiency and salt resistance.

The lean electrolyte in lithium-sulfur (Li-S) batteries commonly presents inhomogeneous distribution and inadequate electrolyte wetting, resulting in uneven electrochemical reaction interface, suboptimal performance, and cell failure or accelerated degradation. Non-destructive operando/in situ methods that can visualize electrolyte wetting and dynamics during cell operation in liquid metal-sulfur batteries have unfortunately not been described. In this study, the operando neutron tomography technique is employed to non-destructively visualize and analyze the electrolyte distribution in practical lean-electrolyte double-layer Li-S pouch cells. Through real-time electrolyte observation across different pouch-cell layers, we unambiguously reveal conglomeration and diminishment of unwetted areas during cell rest, leading to localized electrolyte redistribution. Remarkably, discharge/charge processes can enhance electrolyte homogeneity remarkably, boosting the electrochemical activation of sulfur. Unique periodic "breath-in" and "breath-out" behaviors of electrolyte wetting are observed in the dynamic evolution with the status of discharge and charge, which is correlated to the dissolution and precipitation of sulfur species. These results provide solid evidence of an inhomogeneous distribution of lean electrolyte in practical Li-S pouch cells and offer insights into the correlation between electrolyte redistribution and lithium-sulfur (electro-)chemistry. This work develops valuable guidelines for optimizing testing protocols and strategies for electrolyte wetting in Li-S pouch cells and other metal-sulfur batteries.

Covalent organic frameworks (COFs) have emerged as promising metal-free sulfur hosts to facilitate the conversion kinetics and suppress the shuttling effect of lithium polysulfides (LiPSs) in lithium-sulfur (Li-S) batteries. However, constructing COFs with stable and high electrocatalytic functionality for LiPS conversion remains unexplored. Herein, we develop a radical-cationic COF (R-TTF•+-COF) with superior electrical conductivity of 3.9 S m-1 at room temperature, which features both nucleophilic and electrophilic sites for effective LiPS chemisorption and conversion. With this novel radical-based catalyst, the Li-S battery achieves superior longevity of 1500 cycles with a capacity fading of 0.027% per cycle at a current density of 0.5 C. The capacity retention of the Li-S battery based on R-TTF•+-COF at the current density of 2.0 C is nearly twice as high compared to a COF without radicals. The crucial role of radical cations in catalyzing LiPS conversion has been systematically elucidated through solid-state nuclear magnetic resonance spectroscopy, electron paramagnetic resonance spectroscopy, and theoretical simulations, which verify the reversible interactions between LiPSs and [TTF]2•+ moieties. This intriguing radical-assisted mechanism opens a new avenue for designing efficient catalytic sulfur hosts using organic molecules, offering a significant step toward the practical application of Li-S batteries.

The development of solar-active materials for efficient hydrogen peroxide (H2O2) production remains a critical challenge in artificial photosynthesis. Covalent organic frameworks (COFs) offer a versatile molecular platform for photocatalysis, while constructing efficient charge transfer pathways in COFs to achieve directional transport of photoexcited electrons and enhance photocatalytic performance remains highly challenging. Here, to address this limitation, a new strategy are proposed by incorporating phenanthroline motifs with rigid, conjugated skeletons into 2D triazine-based COFs to enhance charge transfer pathways. Structural and spectroscopic analyses reveal that benzene π-bridges in COF structures activate confined π-electrons in the phenanthroline core, establishing a directional πD-π-A electron transfer pathway. This engineered charge transport system significantly accelerates photocurrent generation and markedly enhances electron mobility. The optimized material achieves an exceptional H2O2 production rate of 40.1 mmol g-1 h-1 under sacrificial conditions, representing a 4.8-fold enhancement over the original COF. The system's versatility is further demonstrated through the complete oxidation of methyl phenyl sulfide within 2 h, with similar efficiency across diverse sulfide derivatives. These findings establish phenanthroline-incorporated COFs as a promising class of photocatalysts for both photocatalytic H2O2 production and organic transformations.

The development of robust catalysts that can work under harsh conditions bring promise but a challenge for photocatalytic hydrogen peroxide production. Here, we report the design of thiazole-based homologous heteropolyaromatic COFs (TTT-COF) via post-cyclization reaction for photocatalytic H2O2 production and aerobic oxidation of C(sp3)-H bonds. Our studies demonstrate that the elemental S heteroatom enables modified COF materials with high chemical stability, continuous π-conjugation, efficient electron and energy transfer, and an enhanced donor-acceptor (D-A) structure and charge separation, thus boosting their intrinsic photocatalytic activities and stability. Consequently, TTT-COF achieves a photosynthetic H2O2 production rate of 29.9 mmol g-1 h-1 with more than 200 hours of long-term stability when employing 10 % benzyl alcohol (V/V) as a sacrificial agent. Notably, the TTT-COF photocatalyst exhibits high reactivity in the oxidation of ethylbenzene derivatives. We believe this strategy offers a promising pathway to synthesize homologous heteropolyaromatic COFs and holds the potential for large-scale production of COF materials with tailored properties for broad applications in photocatalysis and beyond.

Electrochemical NOx- reduction offers an attractive approach for the sustainable production of ammonia (NH3). Copper (Cu)-based materials are commonly used catalysts but suffer from a complex reaction pathway and low NH3 selectivity. Herein, we report an electron delocalization strategy by inducing oxygen vacancy and chlorine (Cl) coordination sites as a dual modulator for the active Cu sites. Our model catalyst (Cu2O1-xCl2) could deliver high NH3 yields over a wide potential window, with a maximum NH3 yield rate of 10.05 mg h-1 cm-2 and a Faradaic efficiency (FE) of 95.1%, exceeding most reported metal catalysts. A combination of experimental and theoretical investigations reveals that the dual modulator induces a favorable electron delocalization around the active Cu sites, resulting in an alteration of the rate-determining step (RDS) from NO2* hydrogenation to the one proton-electron coupling of NO* to form NOH*. This thus enables rapid hydrogenation, avoids the occurrence of side reactions, and significantly improves the selectivity and yield of NH3. When assembled into a membrane electrode electrolyzer, the cell can achieve an industrial current density of 340 mA cm-2 with an NH3 production rate of about 21.36 mg h-1 cm-2 and stably operates for up to 200 h. This RDS regulation strategy provides an innovative solution for enhancing the selectivity and efficiency of target products in electrocatalysis.

In nature, organic molecules play a vital role in light harvesting and photosynthesis. However, regarding artificial water splitting, the research focus is primarily on inorganic semiconductors. Although organic photocatalysts have high structural variability, they tend to exhibit lower quantum efficiencies for water splitting than their inorganic counterparts. Multicomponent reactions (MCRs) offer an attractive route to introduce different functional units into covalent organic frameworks (COFs) and enable semiconducting properties and high chemical stability, creating promising materials for long-term photocatalytic applications, such as H2 production. Herein we present several highly crystalline donor-acceptor based, 4-substituted quinoline-linked MCR-COFs prepared via the three-component Povarov reaction. The pore functionality was varied by applying different vinyl derivatives (e.g. styrene, 2-vinyl pyridine, 4-vinylpyridine, 4-vinyl imidazole, 2,3,4,5,6-pentafluorostyrene), which has a strong influence on the obtained photocatalytic activity. Especially an imidazole-functionalized COF displayed high photocatalytic performance due to its high surface area, crystallinity, and wettability. These properties enable it to maintain its photocatalytic activity even in a membrane support. Furthermore, such MCR-COFs display dramatically enhanced (photo)chemical stability even after long-term solar light irradiation and exhibit a high and steady H2 evolution for at least 15 days.

Photocatalytic H2O2 synthesis from water and oxygen by covalent organic frameworks (COFs) has attracted much attention currently. However, conventional COFs often suffer from insufficient stability and activity due to the unclear structure-activity relationship mechanisms. Herein, a series of quinoline-linked COFs-R (-R = -OH, -OMe, -H, -Br, -CN) synthesized via multi-component reactions (MCRs) is reported to systematically modulate their pore microenvironments and enhance photocatalytic performance. Experimental results reveal that the electron-donating capacity of substituents significantly enhances charge separation efficiency, with H2O2 production activity exhibiting a negative correlation to the Hammett parameters (σp) of the -R groups. Notably, the COF-OH and COF-OMe, bearing the strong electron-donating group, achieve a remarkable H2O2 generation rate of 4458 and 4138 µmol g⁻¹ h⁻¹ in the pure water system. Theoretical calculations confirm that substituents optimize the collective donor structure within the π-conjugated triazine framework, boosting photocatalytic activity. Furthermore, the universal Hammett relationship observed in benzylamine coupling reactions establishes a critical structure-activity model for rational COF design. This work provides fundamental insights into the microenvironment engineering of COFs for efficient H2O2 production and advances the development of sustainable photocatalytic materials.

Ozone (O3) pollution is usually linked to warm weather and strong solar radiation, making it uncommon in cold winters. However, an unusual occurrence of four high O3 episode days (with maximum hourly concentrations exceeding 100 ppbv and peaking at 121 ppbv) was recorded in January 2018 in Lanzhou city, China. During these episodes, the average daytime concentration of total non-methane volatile organic compounds (TVOCs) reached 153.4 +/- 19.0 ppbv, with alkenes-largely emitted from the local petrochemical industry-comprising 82.3 +/- 13.1 ppbv. Here we show a photochemical box model coupled with a Master Chemical Mechanism to elucidate the mechanisms behind this unusual wintertime O3 pollution. We find that the typically low temperatures (-1.7 +/- 1.3 degrees C) and weak solar radiation (263.6 +/- 60.7 W m-2) of those winter episode days had a minimal effect on the reactivity of VOCs with OH radicals. Instead, the ozonolysis of alkenes generated Criegee intermediates, which rapidly decomposed into substantial ROx radicals (OH, HO2, and RO2) without sunlight. This radical production led to the oxidation of VOCs, with alkene ozonolysis ultimately contributing to 89.6 +/- 8.7% of the O3 formation during these episodes. This mechanism did not activate at night due to the depletion of O3 by the NO titration effect. Furthermore, the findings indicate that a reduction of alkenes by 28.6% or NOx by 27.7% in the early afternoon could significantly mitigate wintertime O3 pollution. Overall, this study unravels the unique mechanism of alkene-induced winter O3 pollution and offers a reference for winter O3 reduction strategies in the petrochemical industrial regions. (c) 2024 The Authors. Published by Elsevier B.V. on behalf of Chinese Society for Environmental Sciences, Harbin Institute of Technology, Chinese Research Academy of Environmental Sciences. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Phosphomolybdic acid was used to achieve simultaneously P-doping and heterojunction construction of graphitic carbon nitride. The composite materials show improved light harvesting that result in a better hydrogen evolution performance.

A novel solid polymer electrolyte based on chemically stable vinylene-linked covalent organic framework was developed, demonstrating enhanced Li + conductivity and improved battery performance.

Developing efficient and economical electrocatalysts for acidic oxygen evolution reaction (OER) is essential for proton exchange membrane water electrolyzers (PEMWE). Cobalt oxides are considered promising non-precious OER catalysts due to their high activities. However, the severe dissolution of Co atoms in acid media leads to the collapse of crystal structure, which impedes their application in PEMWE. Here, we report that introducing acid-resistant Ir single atoms into the lattice of spinel cobalt oxides can significantly suppress the Co dissolution and keep them highly stable during the acidic OER process. Combining theoretical and experimental studies, we reveal that the stabilizing effect induced by Ir heteroatoms exhibits a strong dependence on the distance of adjacent Ir single atoms, where the OER stability of cobalt oxides continuously improves with decreasing the distance. When the distance reduces to about 0.6 nm, the spinel cobalt oxides present no obvious degradation over a 60-h stability test for acidic OER, suggesting potential for practical applications.

The ability to molecularly engineer materials may be one of the most powerful tools in favor of high performing heterogeneous catalysts. Porous organic polymers stand out as photocatalysts due to their high chemical stability, outstanding optoelectronic properties and their easy and tunable syntheses. In photocatalysis, the insertion of photosensitizing π-extended molecules into a molecularly well-defined donor-acceptor junctions is supposed to increase the cata-lytic activity, but yet remain experimentally underdeveloped. Here, we present a pyrene-based Covalent Triazine Framework (CTF) synthesized through a polycondensation approach, which was designed to contain a molecularly defined pyrene-triazine-bipyridine donor-acceptor-acceptor triad as the repetition unit of the CTF. The CTF is an efficient photocatalyst for hydrogen evolution from water reaching a production rate of 61.5 mmolH2/h/gcat. Moreover, the same CTF can easily be used as porous macroligand for an organometallic Rh complex to efficiently catalyze the carbon dioxide photoreduction into formic acid under visible light.

The Front Cover illustrates a pyrene- and bipyridine-based covalent triazine framework (CTF) as versatile photocatalyst for the production of different renewable energy vectors. In their Research Article, R. Palkovits, J. Canivet, F. M. Wisser and co-workers demonstrate the crucial role of molecularly defined donor-acceptor-acceptor triad in CTF photocatalysts to enable efficient solar fuel production. Functionalization of the CTF with a platinum co-catalyst enables photocatalytic hydrogen evolution from water with production rates of up to 61.5 mmol H2h-1gcat-1, while functionalization of the same CTF with an organometallic rhodium complex allows for photocatalytic carbon dioxide reduction into formic acid. More information can be found in the Research Article by R. Palkovits, J. Canivet, F. M. Wisser and co-workers.

In this contribution, a simple method for the screening of photocatalytic activity of catalyst materials is presented. The method is based on two steps: the immobilization of the photocatalyst and the subsequent testing of their photocatalytic activity, using the gas evolution at the solid-liquid interface. Up to four catalysts can be tested under the same conditions. The observed gas evolution for selected photocatalysts is consistent with trends reported in the literature from conventional photocatalytic reactors.

Covalent triazine frameworks (CTFs) are a class of porous organic polymers that continuously attract growing interest because of their outstanding chemical and physical properties. However, the control of extended porous organic framework structures at the molecular scale for a precise adjustment of their properties has hardly been achieved so far. Here, we present a series of bipyridine-based CTFs synthesized through polycondensation, in which the sequence of specific building blocks is well controlled. The reported synthetic strategy allows us to tailor the physicochemical features of the CTF materials, including the nitrogen content, the apparent specific surface area, and optoelectronic properties. Based on a comprehensive analytical investigation, we demonstrate a direct correlation of the CTF bipyridine content with the material features such as the specific surface area, band gap, charge separation, and surface wettability with water. The entirety of these parameters dictates the catalytic activity as demonstrated for the photocatalytic hydrogen evolution reaction (HER). The material with the optimal balance between optoelectronic properties and highest hydrophilicity enables HER production rates of up to 7.2 mmol/(h·g) under visible light irradiation and in the presence of a platinum cocatalyst.

Solar-driven water generation is a sustainable water treatment technology, helping to relieve global water scarcity issues. However, this technology faces great challenges due to the high energy consumption of water evaporation yielding low evaporation rates. Here, a covalent organic framework (COF)/graphene dual-region hydrogel, containing hydrophilic and hydrophobic regions in one material, is developed through a facile in situ growth strategy. The hydrophilic COF is covering parts of the hydrophobic graphene regions. Through accurate control of both wetting regions, the hybrid hydrogel shows effective light-harvesting, tunable wettability, optimized water content, and lowered energy demand for water vaporization. Acting as solar absorber, the dual-region hydrogel exhibits a steam generation rate as high as 3.69 kg m(-2) h(-1) under 1 sun irradiation (1 kW m(-2)), which competes well with other state-of-the-art materials. Furthermore, this hydrogel evaporator can be used to produce drinkable water from seawater and sewage, demonstrating the potential for water treatment.