Water Oxygen Research Articles

Increased survival of aquarium fish under acute hypoxia induced by prior intragastric administration of hydrogen peroxide

BACKGROUND: A solution of 3% hydrogen peroxide is an over-the-counter oxygen-releasing antiseptic, which forms oxygen foam when interacting locally with the wound surface. Therefore, this drug is widely used for mechanical cleansing of the surface of chronic wounds from purulent masses. The release of oxygen during catalase cleavage of hydrogen peroxide indicates the possibility of achieving anti-ischemic and anti-hypoxic action. AIM: A study of the effect of intragastric hydrogen peroxide on the resistance of aquarium fish to acute hypoxia. MATERIALS AND METHODS: Experiments were conducted on 80 adult aquarium fish of the guppy, blue neon, tri-linear parsings, swordtail fish and zebrafish (Danio rerio) breeds. To create acute hypoxia, each fish was placed in a transparent plastic container containing 5, 10 or 20 ml of fresh water at a temperature of +25 - +26 °C together with the fish, after which the container was hermetically sealed. Then, the motor activity of the fish's body, the respiratory movements of the gill arches, the opening of the oral cavity, the fluctuations of the fins and the dynamics of their coloration were monitored until the complete final immobilization of the fish and their death. Immediately before the experiment, 0.05 or 0.1 ml of fresh water in the control series and 0.05 ml or 0.1 ml of 0.05% hydrogen peroxide solution in the experimental series were injected into the stomach of the fish. The liquid was injected into the fish's stomach using a gastric mini-probe connected to an insulin syringe. RESULTS: It is shown that aquarium fish retain their viability in a small volume of fresh water inside a hermetically sealed container for a limited period of time, since fish continuously consume oxygen dissolved in water, thereby deepening hypoxia. At the same time, after sealing the container, the fish very quickly assume a stationary state, in which they remain for a certain period of time until their death. However, just before death, the immobility of the fish is disturbed. At the same time, the fish suddenly appear convulsive body movements, active movements of pectoral fins, mouths and gill arches, pectoral fins change their color, after which the fish defecate into the water. The results showed that the preliminary injection of 0.05 or 0.1 ml of 0.05% hydrogen peroxide solution into the stomach of fish prolongs the period of immobility of fish in hypoxia by an average of 20%. In all likelihood, the immobile state of fish is part of the complex of their adaptive adjustment to the cessation of oxygen supply to the water and reflects the availability of reserves of adaptation to hypoxia. The fact is that the absence of muscle contractions stops the muscles from using oxygen, which they use to generate energy. It is assumed that inside the stomach, hydrogen peroxide is absorbed into the blood, where, under the action of the enzyme catalase, it is split into water and gaseous oxygen, which replaces oxygen in the gills in the absence of oxygen in the surrounding water. CONCLUSIONS: Under model conditions, it was shown that pre-administration of 0.05 or 0.1 ml of 0.05% hydrogen peroxide solution into the stomach of fish increases their survival in conditions of acute hypoxia. Therefore, hydrogen peroxide can be considered as a potential antihypoxant for prolonging life in various types of suffocation, including the final stage of COVID-19.

Multi-objective optimization of a pond aeration system using Taguchi-based gray relational analysis

Multi-objective optimization of a pond aeration system using Taguchi-based gray relational analysis

Techno-Economic Feasibility: Planning an On-Grid Solar Power System for Shrimp Pond Aeration

The rapid growth of the Indonesian shrimp farming industry is accompanied by high production costs, primarily driven by the reliance on fossil fuel-based energy sources that can destabilize the ecosystem. This study investigates the technical, economic, and environmental feasibility of using three energy sources, including photovoltaics (PV), grid, and generator, to supply aeration needs in shrimp ponds. A comparative analysis of three scenarios with on-grid schemes was conducted through optimization using Queen Honey Bee Migration (QHBM) and Grey Wolf Optimization (GWO) algorithms, namely Net Present Cost (NPC), Renewable Fraction (RF), and Carbon Emission (ECO2). From a technical point of view, a lower electricity tariff is obtained compared to the grid, which is US$ 589,968. The optimization results on the NPC, RF, and ECO2 parameters show that scenario 1 of the QHBM algorithm is the most optimal. This condition is evidenced by the acquisition of 3 parameters that are closest to the determination of the objective function, yielding an NPC of US$ 230,390.34, RF of 26.01%, and ECO2 of 1,484KgCO2e, with 655Wp PV specifications and the number of PV as many as 578pcs. Economically, the investment in a solar power plant for the shrimp pond obtained BEP of 4.2 years with a payback period (PP) obtained in year 5, net cash-flow of US$ 63,317.31, with ROI of 19% and NPV of US$ 775,159.40 in the same year.

Highly efficient CoAl-LDH/(110) facet-exposed BiOBr catalysts: Promotional effect of Z-type heterojunction and oxygen vacancies in photocatalytic ciprofloxacin degradation

Photocatalysis has received extensive attention as a sustainable technology. Herein, a 2D/2D CoAl-LDH/(110) facet-exposed BiOBr Z-type heterojunction photocatalyst enriched with oxygen vacancies (OVs) and Lewis acid sites was prepared by deposition-precipitation method. Results show that the removal of ciprofloxacin by the optimal heterojunction achieves 88 % within 10 min and 98.6 % within 95 min under visible light. Characterization and DFT calculation reveal that CoAl-LDH induces high-energy (110) crystal plane exposure of BiOBr, resulting in the generation of surface OVs and Lewis acid sites. OVs contribute to the adsorption of dissolved oxygen in water, thereby facilitating the generation of •O2−. And Bi(3−x)+ Lewis acid sites promote the adsorption and degradation of reactant molecules. The charge transfer recombination mechanism of the heterojunction enhances the utilization of photogenerated electrons and holes, improving the catalyst photostability. This work provides a simple method for constructing efficient and stable Z-type heterojunctions with defects for photocatalytic water treatment.

Instrumentation prospects for rocky exoplanet atmospheres studies with high resolution spectroscopy

Studying the atmospheres of exoplanets is one of the most promising ways to learn about distant worlds beyond our solar system. The composition of an exoplanet’s atmosphere can provide critical insights into its geology and potential habitability. For instance, the presence of certain molecules such as water vapor, oxygen, or methane have been proposed to indicate the possibility of life. From an observation point of view, over the past fifteen years, significant progress has been made in characterizing exoplanetary atmospheres. This work reviews recent developments in ground-based high-resolution spectroscopic instruments that make it possible to analyze distant atmospheres in great detail. High-resolution transmission spectroscopy, one of the most effective methods used, has examined the atmospheres of Jupiter-like and is pushing towards the smaller, sub-Neptunian exoplanets. Numerous molecules have been detected using this technique, including CO,H2O,TiO,HCN,CH4,NH3,C2H2,OH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm {CO, H_2O, TiO, HCN, CH_4, NH_3, C_2H_2, OH}$$\\end{document}. We explore the intriguing possibilities that lie ahead for future ground-based instrumentation, particularly in the context of detecting biologically relevant molecules within Earth-analog exoplanetary atmospheres including molecular oxygen (O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm {O_2}$$\\end{document}). With detailed exposure time calculations for detecting O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm {O_2}$$\\end{document} we find that at the same exposure time spectral resolution of 300,000 reaches higher significance compared to 100,000. The exposure time and therefore the needed number of transits is reduced by a factor of 4 in challenging haze and cloud scenarios.

Enlightenment the dynamic behavior of norbornene–modified ’click’ 4–arm polyethylene glycol hydrogel: Delving into framework properties and transport properties through molecular dynamics simulations

The thiol-norbornene cross-linked 4-arm Polyethylene Glycol (PEG) ’click’ hydrogel is a synthetic, sustainable, and bio-inspired polymer extensively used in biomedical applications. Experimental techniques are widely used to study this system, whereas all-atom molecular dynamics simulations, which offer insight into the dynamic behaviours of the system, are never used to study this system. Three models of thiol-norbornene cross-linked PEG ’click’ hydrogel and a base PEG hydrogel are crafted. It is immersed in water to study its structural and transport properties. Structural properties are analysed through root-mean-square deviation (RMSD), radial distribution function (RDF), hydrogen bonds (H-bond), and stress–strain behavior. The RMSD reveals that the norbornene component enhances hydrogel stability compared to the base model. The RDF illustrates interactions between oxygen in PEG chains and water. H-bond results underscore PEG’s strong H-bond acceptance. The norbornene-functionalized crosslinked PEG hydrogel displays maximum H-bonding. It demonstrates a superior swelling ratio attributed to freezing and non-freezing water effects, indicating high stability and potential suitability for applications. Mean square displacements (MSD) unveil the diffusion coefficients of the hydrogel. The base hydrogel model shows the diffusive behavior, and the diffusion coefficient is 1.97 × 10-10 m2/s. The base model has the highest MSD value compared to other systems. The thiol-norbornene crosslinked click hydrogel has the highest Young’s modulus, which signifies the stiffness of the material. Findings illuminate thiol-norbornene ’click’ PEG hydrogel behaviour, emphasising chemical cross-linking’s crucial role in advanced biomedical applications.

MINERALOGICAL, PETROGRAPHIC, AND LITHOCHEMICAL FEATURES OF THE UPPER JURASSIC–LOWER CRETACEOUS SECTION OF THE NORDVIK PENINSULA (NORTH OF EASTERN SIBERIA)

Some intervals of the Jurassic–Cretaceous strata of the Anabar-Lena sedimentary basin have a certain oil and gas production potential, which can be realized in the synchronous offshore horizons of the adjacent territories of the Arctic shelf. Among the most representative objects in this regard are the outcrops of Upper Jurassic and Lower Cretaceous formations of the Nordvik Peninsula. The main data on the composition and structure of this section were obtained mainly at the beginning of the second half of last century. The results of complex mineralogical, petrographic, and lithochemical studies of the Urdyuk-Khaya and Paksa formations of Cape Urdyuk-Khaya of the Nordvik Peninsula presented in here enabled us to identify 10 boundaries for changing of sedimentation regimes of the paleobasin. It was found that the Urdyuk-Khaya Formation was formed mainly in the conditions of the shelf transition zone (moderate deep water) with low rates of terrigenous material intake, some depletion of oxygen in bottom waters, and a trend towards an increase in the depths of the basin. The basal stratum of the Paksa Formation was formed in offshore conditions with periodically occurring dioxic conditions in bottom waters and extremely low rates of terrigenous material intake. The overlying part of the formation was formed in various parts of offshore transition conditions with a gradual decrease in the depths of the basin, an increase in the oxygen content in the bottom layer of water, and the rate of terrigenous material intake. The main provenance area was igneous rocks of mafic, possibly intermediate composition. There was some influence of felsic igneous rocks, or ancient sedimentary rocks rich in quartz. The parent strata were subjected to moderate and severe chemical weathering, in a warm humid climate. The revealed features of the studied strata are similar to the characteristics of the same-age sediments of the lower reaches of the Anabar River, which determines their high correlation potential and allows us to judge the evolution of the western part of the Anabar-Lena basin.

Photocatalytic Decarboxylative Cross-Coupling of α,β-Unsaturated Acids with Amines for α-Ketoamides via C-N Bond Formation.

An unprecedented oxidative decarboxylative chemical domain of α,β-unsaturated acids and amines for C-N cross-coupled α-ketoamidation is disclosed. Molecular oxygen as a source oxygen in amide and water oxygen in the ketone segment furnished a green and sustainable synthesis of α-ketoamide from feedstock acids and amines. Mechanistically, photocatalyst travels with reductive quenching cycle, whereas pallado-cycle proceeded through oxidative C-N bond formation. Broad substrate scope, functional group tolerance, and CO2 and H2O as traceless byproducts make the present methodology more efficient and attractive.

Seasonal variations and altitude effect of oxygen and hydrogen stable isotope ratios of precipitation and spring water in an island of Seto Inland Sea

Seasonal variations and altitude effect of oxygen and hydrogen stable isotope ratios of precipitation and spring water in an island of Seto Inland Sea

Enhanced photocatalytic hydrogen and oxygen evolution activity by two-dimensional van der Waals AlSb/ZnO heterostructure: A first-principles study

Photocatalytic water splitting facilitates the generation of green hydrogen energy by transforming renewable solar energy into chemical energy. This paper investigated the electronic, optical, and photocatalytic properties of AlSb/ZnO van der Waals (vDW) heterostructure using density functional theory. AlSb/ZnO, a semiconductor heterostructure with an indirect bandgap, was energetically stable with a formation energy of −0.4 eV as well as dynamically and thermally stable. The band edges of the 2D heterostructure maintained the essential redox energy levels for complete water splitting, allowing hydrogen and oxygen generation. Moreover, the heterostructure exhibited a high absorption coefficient in the visible region of the solar spectrum compared to the individual AlSb and ZnO monolayers. We revealed low barrier potential at neutral pH conditions for oxygen and hydrogen evolution reactions from the Gibbs free energy calculation without any external potential. Our study additionally showed the solar-to-hydrogen efficiency of 27.93% and a carrier utilization efficiency of 42.83%, indicating the AlSb/ZnO heterostructure as an excellent water splitting photocatalyst with remarkable potential for fuel cells and energy storage applications.

Citicoline eluting hydrogels for therapeutic contact lenses intended to treat neurodegenerative diabetic ocular diseases

Ophthalmic neurodegenerative diseases related to diabetes, such as glaucoma and retinopathy, are among the major causes of blindness in the world. Citicoline (CIT) in the form of eye drops is currently used for the treatment/prevention of these diseases, which affect the posterior segment of the eye. To ensure the drug penetration into the back of the eye, frequent instillations of highly concentrated drug solutions are required with potential side effects. Drug-loaded soft contact lenses (SCLs) may be an effective alternative to the conventional eye drop treatment, since they may enable a sustained drug release during daily wear, ensuring a higher drug bioavailability, and avoiding drug waste. In this work, one 2-hydroxyethyl methacrylate (HEMA) based hydrogel was functionalised with N-(3-aminopropyl) methacrylamide hydrochloride (APMA), molecularly imprinted with CIT and loaded with the same drug. The material was extensively characterised, in terms of morphology, optical, mechanical, and physical–chemical properties, namely, equilibrium water content, wettability, oxygen and ionic permeability, Young’s modulus, shear deformation, transmittance and refractive index, before and after steam sterilisation. Additionally, the tendency of the material to adsorb proteins of the lachrymal fluid was evaluated and its biocompatibility was assessed by irritation and cytotoxicity assays. Comparison with the non-functionalised and non-imprinted hydrogel showed that the modified hydrogel led to a sustained in vitro release of a much higher amount of CIT than the original one, while keeping typical values for physical–chemical properties of SCLs. The drug-loaded material resisted steam sterilisation and proved to be biocompatible, demonstrating adequate properties to be used in therapeutic SCLs for the prophylaxis/treatment of neurodegenerative diabetic ocular diseases. The neuroprotective effect of the released drug was confirmed with tests using porcine retinal explants.

Rapid Eutrophication of a Clearwater Lake: Trends and Potential Causes Inferred From Phosphorus Mass Balance Analyses.

Many clearwater lakes increasingly show symptoms of eutrophication, but the underlying causes are largely unknown. We combined long-term water chemistry data, multi-year sediment trap measurements, sediment analyses and simple mass balance models to elucidate potential causes of eutrophication of a deep temperate clearwater lake, where total phosphorus (TP) concentrations quadrupled within a decade, accompanied by expanding hypolimnetic anoxia. Discrepancies between modeled and empirically determined P inputs suggest that the observed sharp rise in TP was driven by internal processes. The magnitude of seasonal variation in TP greatly increased at the same time, both in surface and deep water, partly decoupled from deep water oxygen conditions. A positive correlation between annual P loss from the upper water column and hypolimnetic P accumulation could hint at a short-circuited P cycle involving lateral TP transport from shallow-water zones and deposition and release from sediments in deep water. This hypothesis is also supported by P budgets for the upper 20 m during stable summer stratification, suggesting that sediments in shallow lake areas acted as a P net source until 2018. These changes are potentially related to shifts in submerged macrophytes from wintergreen charophyte meadows (Nitellopsis obtusa) to annual free-floating hornwort (Ceratophyllum demersum) and to increased sulfide formation, promoting iron fixation in the sediments. Iron bound to sulfur is unavailable for binding P, resulting in a positive feedback between P release in shallow lake areas, primary productivity, macrophyte community structure and redox-dependent sediment biogeochemistry. Overall, our results suggest that relationships more complex than the commonly invoked increase in internal P release under increasingly anoxic conditions can drive rapid lake eutrophication. Since the proportion of littoral areas is typically large even in deep stratified lakes, littoral processes may contribute more frequently to the rapid lake eutrophication trends observed around the world than is currently recognized.

Modulating Electrolyte Solvation Structure for High‐Voltage and Low‐Temperature Magnesium‐ion Supercapacitors

Aqueous electrolytes supercapacitors have great potential in energy storage devices due to their high‐power density and safety. However, due to the water hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), the electrochemical stabilization window of aqueous electrolytes needs to be widened. Moreover, the application of aqueous electrolyte at low temperature is often limited by the freezing point of water. In this paper, we modulate the solvation structure of aqueous magnesium‐ion supercapacitors by using sulfolane as a co‐solvent. The modulated low salt concentration hybrid electrolyte extends the electrochemical stability window of the electrolyte to 2.9V and enhances the stability of the electrolyte at extreme temperatures, as well as provides safe and non‐flammable properties. Based on the hybrid electrolyte, the water‐organic hybrid magnesium‐ion supercapacitors (HMSCs) are able to operate within an enlarged voltage range of 0 – 2.2 V at a low temperature of ‐30°C. The HMSC shows a specific capacitance of up to 58 F/g at room temperature and retains a specific capacitance of 39 F/g at a current density of 15 A/g. Furthermore, it has an outstanding cycling performance at ‐30 °C, maintaining a specific capacitance of more than 92% after 20,000 cycles.

Ab Initio Molecular Dynamics Studies of Stacked Adenine–Thymine and Guanine–Cytosine Nucleic Acid Base Pairs in Aqueous Solution

Ab initio MD studies have been performed on stacked adenine–thymine (A–T) and guanine–cytosine (G–C) nucleobase pairs solvated in water using Born–Oppenheimer molecular dynamics. These two systems have been analyzed using RDF, SDF, angle–distance CDF (combined distribution functions), plane projection analysis, hydrogen bond analysis, and non–covalent interaction (NCI) plots. The stacking property studies have shown that the molecular orientation of the A–T pair is completely opposite to that of the G–C pair though the center of mass distance between the two molecules is similar. The G–C pair shows significantly more stability in water than the A–T system does. RDF analyses show that the –NH– group and carbonyl groups show predominant interaction with water molecules. Water molecules are found to be most in numbers around the cytosine molecule and least around the adenine molecule. Hydrogen bonding studies show that the guanine molecule forms the highest number of hydrogen bonds with water molecules. On the other hand, the hydrogen atom attached to the –NH– group of adenine molecule shows the longest mean H–bond lifetime with water oxygen atoms. NCI interactions calculated through the ab initio method help us to visualize the [Formula: see text]-electron stacking and H–bonding between aromatic nucleobases and water molecules. A great shift in bond polarity and interaction intensity in different functional groups is observed for the nucleobases going from individually solvated molecules to paired states.

Seasonal shifts in depth-to-water uptake by young thinned and overstocked lodgepole pine (Pinus contorta) forests under drought conditions in the Okanagan Valley, British Columbia, Canada

Abstract. As drought and prolonged water stress become more prevalent in dry regions under climate change, preserving water resources becomes a focal point for maintaining forest health. Forest regeneration after forest loss or disturbance can lead to overstocked juvenile stands with high water demands and low water-use efficiency. Forest thinning is a common practice with the goal of improving tree health, carbon storage, and water use while decreasing stand demands in arid and semi-arid regions. However, little is known about the impacts of stand density on seasonal variation in depth-to-water uptake or the magnitude of the effect of growing season drought conditions on water availability. Existing reports are highly variable by climatic region, species, and thinning intensity. In this study, stable isotope ratios of deuterium (δ2H) and oxygen (δ18O) in water collected from various soil depths and from branches of lodgepole pine (Pinus contorta) under different degrees of thinning (control: 27 000 stems per hectare; moderately thinned: 4500 stems per hectare; heavily thinned: 1100 stems per hectare) over the growing season were analyzed using the MixSIAR Bayesian mixing model to calculate the relative contributions of different water sources in the Okanagan Valley in the interior of British Columbia, Canada. We found that under drought conditions the lodgepole pine trees shifted their depth-to-water uptake through the growing season (June to October) to rely more heavily on older precipitation events that percolated through the soil profile when shallow soil water became less accessible. Decreased forest density subsequent to forest thinning did not cause a significant difference in the isotopic composition of branch water but did cause changes in the timing and relative proportion of water utilized from different depths. Thinned lodgepole pine stands were able to maintain water uptake from 35 cm below the soil profile, whereas the overstocked stands relied on a larger proportion of deep soil water and groundwater towards the end of the growing season. Our results support other findings by indicating that, although lodgepole pines are drought-tolerant and have dimorphic root systems, they do not shift back from deep water sources to shallow soil water when soil water availability increases following precipitation events at the end of the growing season.

Structure, Stability, and Activity of Titania-Supported VOx in the Presence of Oxygen Vacancies and Adsorbed Water or Atomic Oxygen

Structure, Stability, and Activity of Titania-Supported VO_<i>x</i> in the Presence of Oxygen Vacancies and Adsorbed Water or Atomic Oxygen

Ecohydrological role of groundwater outflows in the functioning of the ecotone zone in Lake Jaczno, Poland

The research determined the influence of natural groundwater outflows from the spring peat bog on the water supply and its quality in Lake Jaczno. Lake Jaczno is located in the Suwalski Landscape Park (SLP) in the Podlaskie Voivodeship, north-east Poland. The research was conducted from April 2009 to October 2010 and from September 2022 to September 2023. Water samples were collected from spring areas, shallow groundwater, and from Lake Jaczno. Fieldwork involved measuring flow, temperature, water electrolytic conductivity (EC), dissolved oxygen (DO) concentration, water oxygen saturation (WS), and water reaction (pH). Chemical analyses of water samples were carried out in the laboratory. Findings indicate that groundwater, spring water, and lake water in the SLP maintain high quality, with no significant changes in chemical composition over the past decades. Additionally, the physical water parameters display low temporal variability. The EC in the tested waters oscillates around 500 μS∙cm–1. Both spring and lake waters are well oxygenated (97–100%). Biogenic element concentrations exhibit higher variability, influenced by flora development in areas with natural groundwater outflows. High oxygenation of water contributes to increased concentrations of nitrates. The analysed waters exhibited similarity in the concentration and structure of phosphorus forms. Additionally, sediment chemical parameters at Lake Jaczno suggests a buffering capacity in the transitional zones between water and land. Despite similarities in chemical composition, sediment granulometry suggests low permeability, potentially restricting exchange between groundwater and surface waters. Monitoring springs in these environments is important due to their impact on quantity and quality of water in the analysed areas.

Celebrating Ten Years of Covalent Organic Frameworks for Solar Energy Conversion: Past, Present and Future

AbstractAccelerated anthropogenic emission of greenhouse gases due to increasing energy demands has created a negative impact on our planet. Therefore, the replacement of fossil by renewable energy resources has become of paramount interest, both societally and scientifically. It is within this setting that organic photocatalysts have emerged as a new generation of earth‐abundant catalysts for the conversion of solar radiation into chemical energy. In 2014, the first example of a covalent organic framework (COF) photocatalyst for the hydrogen evolution reaction was reported by our group, which has not only marked the beginning of COF photocatalysis for solar fuel production but also helped to accelerate research into “soft photocatalysis” based on porous polymers in general. In the last decade, significant progress has been made toward developing COFs as robust, molecularly precise platforms emulating artificial photosynthesis. This mini‐review commemorates the 10th anniversary of COF photocatalysis and gives a brief historical overview of the milestones in the field since its inception in 2014. We review milestones in the development of COFs for solar fuel production and related photocatalytic transformations, including hydrogen evolution, oxygen evolution, overall water splitting, CO2 reduction, N2 fixation, oxygen reduction, and alcohol oxidation. We discuss lessons learned for the design of structure‐property‐function relationships in COF photocatalysts, and future perspectives and challenges for the field of “soft photocatalysis” are given.

Celebrating Ten Years of Covalent Organic Frameworks for Solar Energy Conversion: Past, Present and Future.

Accelerated anthropogenic emission of greenhouse gases due to increasing energy demands has created a negative impact on our planet. Therefore, the replacement of fossil by renewable energy resources has become of paramount interest, both societally and scientifically. It is within this setting that organic photocatalysts have emerged as a new generation of earth-abundant catalysts for the conversion of solar radiation into chemical energy. In 2014, the first example of a covalent organic framework (COF) photocatalyst for the hydrogen evolution reaction was reported by our group, which has not only marked the beginning of COF photocatalysis for solar fuel production but also helped to accelerate research into "soft photocatalysis" based on porous polymers in general. In the last decade, significant progress has been made toward developing COFs as robust, molecularly precise platforms emulating artificial photosynthesis. This mini-review commemorates the 10th anniversary of COF photocatalysis and gives a brief historical overview of the milestones in the field since its inception in 2014. We review milestones in the development of COFs for solar fuel production and related photocatalytic transformations, including hydrogen evolution, oxygen evolution, overall water splitting, CO2 reduction, N2 fixation, oxygen reduction, and alcohol oxidation. We discuss lessons learned for the design of structure-property-function relationships in COF photocatalysts, and future perspectives and challenges for the field of "soft photocatalysis" are given.

Chain-End Controlled Depolymerization Selectivity in α,α-Disubstituted Propionate PHAs with Dual Closed-Loop Recycling and Record-High Melting Temperature.

Within the large poly(3-hydroxyalkanoate) (PHA) family, C3 propionates are much less studied than C4 butyrates, with the exception of α,α-disubstituted propionate PHAs, particularly poly(3-hydroxy-2,2-dimethylpropionate), P3H(Me)2P, due to its high melting temperature (Tm ∼ 230 °C) and crystallinity (∼76%). However, inefficient synthetic routes to its monomer 2,2-dimethylpropiolactone [(Me)2PL] and extreme brittleness of P3H(Me)2P largely hinder its broad applications. Here, we introduce simple, efficient step-growth polycondensation (SGP) of a hydroxyacid or methyl ester to afford P3H(Me)2P with low to medium molar mass, which is then utilized to produce lactones through base-catalyzed depolymerization. The ring-opening polymerization (ROP) of the 4-membered lactone leads to high-molar-mass P3H(Me)2P, which can be depolymerized by hydrolysis to the hydroxyacid in 99% yield or methanolysis to the hydroxyester in 91% yield, achieving closed-loop recycling via both SGP and ROP routes. Intriguingly, the chain end of the SGP-P3H(Me)2P determines the depolymerization selectivity toward 4- or 12-membered lactone formation, while both can be repolymerized back to P3H(Me)2P. Through the formation of copolymers P3H(Me/R)2P (R = Et, nPr), PHAs with high tensile strength and ductility, coupled with high barriers to water vapor and oxygen, have been created. Notably, the PHA structure-property study led to P3H(nPr)2P with a record-high Tm of 266 °C within the PHA family.