2p States Research Articles

Investigation of kaonic atom optical potential by the high precision data of kaonic 3He and 4He atoms

Abstract We investigate kaonic atom optical potentials of 3He and 4He phenomenologically based on the latest high precision data of the 2p states of the kaonic atoms in helium (J-PARC E62). We consider a simple phenomenological form for the optical potential proportional to the nuclear density distributions and clarify the meanings and implications of the data by determining the potential parameters by the latest data. We find two sets of potential parameters for each of K− − 3He and K− − 4He that reproduce the data. We then extract the potential parameters consistent with the data of 3He and 4He atoms simultaneously. We report the possible strong isospin dependence of the potential, and the different strength of the data of K− − 3He and K− − 4He in the restrictions on the potential parameters. We mention that the study of the 1s states of the kaonic helium atom is very interesting as a next step. Observing these states could provide valuable information on potential parameters and kaonic nuclear s states because of the mutual influence between the atomic and the nuclear states of kaon with the same orbital angular momentum.

Tailored pseudopotentials for magnesium surface core level shift calculations

In x-ray photoelectron spectroscopy (XPS), identifying the origin of peaks in the spectrum can be guided by theory calculations. With density functional theory (DFT), using pseudopotentials, one can obtain the difference in photoelectron energy for electrons originating from atoms of different environments, for example surface and bulk atoms, and thus model the surface core level shift (SCLS) energies. The focus in this work is to prepare for calculations of magnesium (Mg) 2p SCLSs in material systems where dispersion interactions play a role, primarily in Mg surface degradation and adsorption of molecules as relevant, for example, in degradable bioimplants. For SCLS DFT calculations in metallic surfaces, the state of the photoelectron must be treated as a core state. In the case of Mg, standard pseudopotentials treat the 2p state as a valence state, not a core state. We therefore need Mg pseudopotentials with the 2p electrons in the core, leaving only two electrons for the valence region (the 3s electron); Two-valence electron pseudopotentials are not common, because DFT calculations of Mg-containing materials usually are better or more easily described using 10 valence electrons. In this work, new two-electron Mg pseudopotentials are therefore created for use in dispersion-inclusive DFT calculations. To our knowledge, no such two-electron Mg pseudopotentials exist, proven to work well with the nonlocal, dispersion-inclusive, exchange-correlation functional vdW-DF-cx or similar functionals. We create a number of two-electron Mg pseudopotentials and their 2p-hole partners, and for four of the most promising we assess their performance in vdW-DF-cx. We provide results for Mg and MgO bulk phases and for the Mg(0001) surface energy, structure, and SCLS, and where possible we compare with results that we obtain by using conventional 10-electron Mg pseudopotentials, all-electron calculations, and with experiments. This work not only reports and tests the specific conditions for creating 2p Mg results, it will also, we believe, be of help in creating other similar pseudopotentials to aid the analysis of XPS spectra in other materials. Published by the American Physical Society 2024

Validation of quantum espresso software in estimating the optical parameters of CaAlSiN3 crystal

This communication presents a theoretical analysis of certain optical properties of the CaAlSiN3 (CASN) crystal through first principles calculation. For the first time, this work validates the optical properties of the crystal performed using Quantum ESPRESSO (Acronym for opEn-Source Package for Research in Electronic Structure, Simulation, and Optimization) Plane Wave Self Consistent Field (PWscf). The calculated optical joint density of states show that the absorption begins at 4.8 eV and exhibits two sharp peaks and one broad peak at 48 nm, 64 nm, and 170 nm. The absorption range is in good agreement with our experimental observations. The dielectric function shows electric polarization between the 2p state of nitrogen and 3d state of calcium. The crystal’s static refractive index is 1.87 with a maximum value of 6.4 in the visible region, which is optimal for optical devices. The absorption coefficient confirms experimentally comparable optical states with no notable anisotropy.

Theoretical analysis of argon 2p states' density ratios for nanosecond plasma optical emission spectroscopy

A theoretical analysis of excited argon state densities responsible for optical emission spectra of atmospheric pressure argon plasma is presented for its use in plasma diagnostics. Nanosecond pulsed barrier discharges are simulated using spatially one- and two-dimensional fluid-Poisson models using the reaction kinetics model presented by Stankov et al. [1], which considers all ten argon 2p states (Paschen notation) separately. The very first (single) discharge and repetitive discharges with frequencies from 5 kHz to 100 kHz are considered. A semi-automated procedure is utilized to find appropriate 2p states for electric field determination using an intensity ratio method, which is based on a time-dependent collisional-radiative model. The fluid simulations in combination with the semi-automated procedure are used to quantify the sensitivity of selected 2p-state ratios to given preionization of the gas. A highly sensitive time-correlated single photon counting experiment shows clearly that the selected ratio is sensitive to the electric field variation in the streamer head, yet additional calibration is needed for absolute values determination. Different approaches for effective lifetime determination are tested and applied also to measured data. The influence of radial and axial 2p state density integration on the intensity ratio method is discussed. The above mentioned models and procedures result in a flexible theory-based methodology applicable for development of new diagnostic techniques.

Structural properties, thermodynamic stability and reaction pathways for solid-state synthesis of Bi2WO6 polymorphs.

This study presents a density functional theory (DFT) investigation into the structural, electronic, and optical properties, thermodynamic stability, phase competition, and reaction pathways of Bi2WO6, a notable compound within the Aurivillius family of oxides. We examine three distinct polymorphs of Bi2WO6: the low-temperature orthorhombic phase (P1), the intermediate-temperature orthorhombic phase (P2), and the high-temperature monoclinic phase (P3). Electronic structure analysis indicates band gaps of 2.339 eV (P1), 2.312 eV (P2), and 2.128 eV (P3), with the valence band primarily composed of O 2p states and the conduction band of Bi 6p and W 5d states. Optical properties, including the dielectric function and absorption spectra, show distinct behaviors for each phase, particularly P3. Elastic and phonon property analyses confirm the mechanical and dynamical stability of all three phases, with the P1 phase exhibiting the highest bulk modulus and stiffness among the polymorphs. Our effective mass calculations suggest that the P3 phase may have better charge carrier mobility compared to the P1 and P2 phases. Structural optimizations reveal marginal differences in total energy among these phases, suggesting their potential coexistence or easy phase transitions under varying conditions. Detailed Gibbs free energy calculations confirm that the P1 phase is the most stable at low temperatures, in agreement with experimental data in the literature. We also construct a chemical reaction network to explore feasible reaction pathways for the solid-state synthesis of Bi2WO6 from Bi2O3 and WO3 precursors, identifying several low-cost reaction pathways, including both direct and multi-step routes involving intermediates such as Bi14WO24 and Bi2W2O9.

Cross-luminescence in BaF[formula omitted] crystals doped with M[formula omitted] and RE[formula omitted] ions: Hybrid density functional theory study

Radiation resistant inorganic materials emitting cross-luminescence are one of the most prospective candidates for new generation ultrafast detectors for medical tomography. Radiative transitions leading to cross-luminescence occur between valence and core states, and therefore calculations of the electronic structure of doped materials can explain ultrafast transitions and predict new cross-luminescent materials. In current work we demonstrate results of ab initio calculations of undoped and doped BaF2 by means of hybrid density functional theory. As a result of the work, the density of states (DOS) for nominally pure BaF2 and a whole series of BaF2 doped with various trivalent ions were obtained. The positions of the core energy levels of dopant ions lying between the Ba(5p) zone and the F(2s) zone, as well local geometries and formation energies were calculated. Our calculations show that the 5p states of impurity ions can be located below the 5p zone of barium by several eV. This opens up opportunities for transitions from the core 5p Ba zone to impurity 5p states, which might be involved in experimentally observed appearance of an ultrafast component in doped BaF2.

Cementite with substitutional Nb atoms based on first-principles calculations

Abstract Cementite is the strengthening phase in pearlite, and its mechanical properties determine the strength of the pearlite. A crystal model of niobium-substituted Fe3C was constructed. The stability, charge density, and elastic constants of the model were calculated, and the effects of niobium (Nb) substitution on the properties of Fe3C were discussed. FeNb8d 2C is the most stable Nb-substituted structure. The reaction energy of FeNb8d 2C is -0.796 eV, with a magnetic moment of 0.07 μB/f.u. At the Fermi level, the DOS of FeNb8d 2C is 4.24, displaying metallic properties. Nb substitution enhances the symmetry of the DOS in Fe3C. The covalent bonding in FeNb8d 2C, predominantly consisting of σ and π bonds, is formed by the hybridization of Nb 3d states and C 2p states. FeNb8d 2C is mechanical stability. It exhibits the strongest resistance to linear compression along the [100] direction and the highest shear deformation resistance along the (010) plane. Nb substitution increases the toughness of Fe3C, enhances isotropy on the (010) plane, and improves the resistance to linear compression along the [010] direction.

Circular dichroism in multiphoton ionization of resonantly excited helium ions near channel closing

The circular dichroism (CD) of photoelectrons generated by near-infrared (NIR) laser pulses using multiphoton ionization of excited He+ ions in the 3p(m= +1) state is investigated. The ions were prepared by circularly polarized extreme ultraviolet (XUV) pulses. For circularly polarized NIR pulses co- and counter-rotating relative to the polarization of the XUV pulse, a complex variation of the CD is observed as a result of intensity- and polarization-dependent Freeman resonances, with and without additional dichroic AC-Stark shifts. The experimental results are compared with numerical solutions of the time-dependent Schrödinger equation to identify and interpret the pronounced variation of the experimentally observed CD.

Al-N3 Bridge Site Enabling Interlayer Charge Transfer Boosts the Direct Photosynthesis of Hydrogen Peroxide from Water and Air.

Manipulating the electronic environment of the reactive center to lower the energy barrier of the rate-determining water oxidation step for boosting the direct generation of H2O2 from water, air, and sunlight is fascinating yet remains a grand challenge. Driven by a first-principles screening across a series of metal single atoms in carbon nitride, we report a class of an Al-N3 bridge site enabling interlayer charge transfer in carbon nitride nanotubes (CNNT-Al) for the highly efficient photosynthesis of H2O2 directly from water, oxygen, and sunlight. We demonstrate that the interlayered Al-N3 bridge site in CNNT-Al is able to activate the neighboring surface N atom for promoting the rate-determining step of the two-electron water oxidation to H2O2. It is also able to act as a bridge for enhancing the vertical interlaminar charge transfer due to the hybridization between the 3s and 3p states of the interstitial Al atom and the conduction band of two adjacent carbon nitride layers. Collectively, these factors lead to a highest photocatalytic mass activity of 1410.2 μmol g-1 h-1 (with a photocatalyst concentration of 1 g L-1) for direct photosynthesis of H2O2 out of all CN-based photocatalysts and a 7-fold higher solar-to-chemical conversion efficiency (0.73%) compared to that of the natural photosynthesis of typical plants (∼0.1%). Most importantly, the CNNT-Al-based flow reactor can steadily produce H2O2 for 200 h and be directly used for the on-site degradation of organic dye in water. The CNNT-Al-based flow reactor can also kill a 10 times higher concentration of bacteria in deionized water than that in natural water with 100% efficiency, which makes our design economically appealing for practical water treatment.

Physicochemical properties of La0.5Ba0.5Co1-xFexO3-δ (0 ≤ x ≤ 1) as positrode for proton ceramic electrochemical cells

We report on essential properties of materials in the series La0.5Ba0.5Co1-xFexO3-δ as positrodes for proton ceramic electrochemical cells (PCECs). The unit cell and thermochemical expansion coefficient (TCEC) of these cubic perovskites decrease with iron content x, the TCEC of La0.5Ba0.5FeO3-δ going as low as 11·10-6 1/K. The materials behave as LaMO3 perovskites with small band gaps and Ba acting as acceptors compensated by electron holes and oxygen vacancies. The electrical properties are dominated by p-type conduction with high large polaron mobilities for the Co-rich compositions at low temperatures, shifting towards small polaron mobilities with increasing Fe content. X-ray absorption spectroscopy (XAS) shows that Co is in a high spin state and takes on the main part of the cation oxidation state changes, and that hole states are in orbitals overlapping with the O 2p states, confirming the large polaronic behaviour, while holes on Fe are more localised at the cation. Hydration is more pronounced in inert atmospheres, as hydration of oxygen vacancies is easier than hydrogenation and increases with Fe content, in line with the commonly accepted finding that delocalization of holes disfavours protonation. Fe-rich compositions benefit from lower TCEC and higher hydration and hence expected proton permeability, at the cost of lower electronic conductivity. The surfaces are hydrophobic irrespective of Fe content, suggesting weak chemisorption of the underlaying water layer, possibly giving relatively many available surface sites for oxygen adsorption, but limited surface proton conductance – both of importance to positrodes for operando PCECs.

Harnessing the Unconventional Cubic Phase in 2D LaNiO3 Perovskite for Highly Efficient Urea Oxidation

AbstractPhase engineering is a critical strategy in electrocatalysis, as it allows for the modulation of electronic, geometric, and chemical properties to directly influence the catalytic performance. Despite its potential, phase engineering remains particularly challenging in thermodynamically stable perovskites, especially in a 2D structure constraint. Herein, we report phase engineering in 2D LaNiO3 perovskite using the strongly non‐equilibrium microwave shock method. This approach enables the synthesis of conventional hexagonal and unconventional trigonal and cubic phases in LaNiO3 by inducing selective phase transitions at designed temperatures, followed by rapid quenching to allow precise phase control while preserving the 2D porous structure. These phase transitions induce structural distortions in the [LaO]+ layers and the hybridization between Ni 3d and O 2p states, modifying local charge distribution and enhancing electron transport during the six‐electron urea oxidation process (UOR). The cubic LaNiO3 offers optimal electron transport and active site accessibility due to its high structural symmetry and open interlayer spacing, resulting in a low onset potential of 1.27 V and a Tafel slope of 33.1 mV dec−1 for UOR, outperforming most current catalysts. Our strategy features high designability in phase engineering, enabling various electrocatalysts to harness the power of unconventional phases.

Harnessing the Unconventional Cubic Phase in 2D LaNiO3 Perovskite for Highly Efficient Urea Oxidation

AbstractPhase engineering is a critical strategy in electrocatalysis, as it allows for the modulation of electronic, geometric, and chemical properties to directly influence the catalytic performance. Despite its potential, phase engineering remains particularly challenging in thermodynamically stable perovskites, especially in a 2D structure constraint. Herein, we report phase engineering in 2D LaNiO3 perovskite using the strongly non‐equilibrium microwave shock method. This approach enables the synthesis of conventional hexagonal and unconventional trigonal and cubic phases in LaNiO3 by inducing selective phase transitions at designed temperatures, followed by rapid quenching to allow precise phase control while preserving the 2D porous structure. These phase transitions induce structural distortions in the [LaO]+ layers and the hybridization between Ni 3d and O 2p states, modifying local charge distribution and enhancing electron transport during the six‐electron urea oxidation process (UOR). The cubic LaNiO3 offers optimal electron transport and active site accessibility due to its high structural symmetry and open interlayer spacing, resulting in a low onset potential of 1.27 V and a Tafel slope of 33.1 mV dec−1 for UOR, outperforming most current catalysts. Our strategy features high designability in phase engineering, enabling various electrocatalysts to harness the power of unconventional phases.

Unraveling the Anionic Redox Chemistry in Aqueous Zinc‐MnO2 Batteries

AbstractActivating anionic redox reaction (ARR) has attracted a great interest in Li/Na‐ion batteries owing to the fascinating extra‐capacity at high operating voltages. However, ARR has rarely been reported in aqueous zinc‐ion batteries (AZIBs) and its possibility in the popular MnO2‐based cathodes has not been explored. Herein, the novel manganese deficient MnO2 micro‐nano spheres with interlayer “Ca2+‐pillars” (CaMnO‐140) are prepared via a low‐temperature (140 °C) hydrothermal method, where the Mn vacancies can trigger ARR by creating non‐bonding O 2p states, the pre‐intercalated Ca2+ can reinforce the layered structure and suppress the lattice oxygen release by forming Ca−O configurations. The tailored CaMnO‐140 cathode demonstrates an unprecedentedly high rate capability (485.4 mAh g−1 at 0.1 A g−1 with 154.5 mAh g−1 at 10 A g−1) and a marvelous long‐term cycling durability (90.6 % capacity retention over 5000 cycles) in AZIBs. The reversible oxygen redox chemistry accompanied by CF3SO3− (from the electrolyte) uptake/release, and the manganese redox accompanied by H+/Zn2+ co‐insertion/extraction, are elucidated by advanced synchrotron characterizations and theoretical computations. Finally, pouch‐type CaMnO‐140//Zn batteries manifest bright application prospects with high energy, long life, wide‐temperature adaptability, and high operating safety. This study provides new perspectives for developing high‐energy cathodes for AZIBs by initiating anionic redox chemistry.

Unraveling the Anionic Redox Chemistry in Aqueous Zinc-MnO2 Batteries.

Activating anionic redox reaction (ARR) has attracted a great interest in Li/Na-ion batteries owing to the fascinating extra-capacity at high operating voltages. However, ARR has rarely been reported in aqueous zinc-ion batteries (AZIBs) and its possibility in the popular MnO2-based cathodes has not been explored. Herein, the novel manganese deficient MnO2 micro-nano spheres with interlayer "Ca2+-pillars" (CaMnO-140) are prepared via a low-temperature (140 °C) hydrothermal method, where the Mn vacancies can trigger ARR by creating non-bonding O 2p states, the pre-intercalated Ca2+ can reinforce the layered structure and suppress the lattice oxygen release by forming Ca-O configurations. The tailored CaMnO-140 cathode demonstrates an unprecedentedly high rate capability (485.4 mAh g-1 at 0.1 A g-1 with 154.5 mAh g-1 at 10 A g-1) and a marvelous long-term cycling durability (90.6 % capacity retention over 5000 cycles) in AZIBs. The reversible oxygen redox chemistry accompanied by CF3SO3 - (from the electrolyte) uptake/release, and the manganese redox accompanied by H+/Zn2+ co-insertion/extraction, are elucidated by advanced synchrotron characterizations and theoretical computations. Finally, pouch-type CaMnO-140//Zn batteries manifest bright application prospects with high energy, long life, wide-temperature adaptability, and high operating safety. This study provides new perspectives for developing high-energy cathodes for AZIBs by initiating anionic redox chemistry.

Observation of reversible conformational interconversion accompanied by 3p internal conversions in Rydberg-excited N,N-dimethylethylamine

Conformational dynamics has been well observed in the 3s Rydberg state of amines, whereas its observation in higher-energy, non-equilibrium 3p Rydberg states is very rare, especially for a reversible conformational transition that could compete with other non-adiabatic transitions. Herein, we report the observation of a reversible conformational interconversion phenomenon in the 3p Rydberg excited-state dynamics of N,N-dimethylethylamine (DMEA). Upon electronic excitation, a forward and backward interconversion between the initially prepared 3p_l and 3p_h conformers accompanied by 3p internal conversions occurs, resulting in a 3p_l/3p_h equilibrium ratio of 61 %/39 % within ∼1.5 ps. The ensuing parallel internal conversions from the 3p_l to 3s_l and 3p_h to 3s_h deposit about 1.80 eV of vibrational energy into the 3s state, enabling a fast conformational interconversion between the 3s_h and 3s_l conformers to proceed within ∼2.0 ps. The final 3s_l/3s_h equilibrium ratio was determined to be 76 %/24 %. This work presents a real-time observation of the entire conformational interconversion process initiating from the higher-energy 3p states and finally reaching an equilibrium on the lower-energy 3s state.

Electronic, optical, phonon, and thermodynamic properties of bismuth oxyhalides for photocatalysis application using density functional theory

Bismuth oxyhalide (BiOX) represents a class of layered materials distinguished by unique physicochemical and optical characteristics. This study delivers an extensive investigation into the properties of BiOX crystals, employing first-principles calculations to analyze the electronic band structure, projected density of states (PDOS), Raman and infrared (IR) spectra, dielectric functions, alongside phonon and thermodynamic properties. The computed electronic band gaps BiOI, BiOBr, BiOCl, and BiOF crystals were determined to be 2.19 eV, 3.05 eV, 3.29 eV, and 3.43 eV, respectively. Furthermore, an analysis of the PDOS for each BiOX type indicates that the valence band maximum (VBM) primarily comprises dominant O 2p and halide X np states, while the conduction band minimum (CBM) predominantly features Bi 6p states. In addition, significant absorption edges for BiOI, BiOBr, BiOCl, and BiOF crystals, oriented along the [100] axis, were observed at wavelengths of 540 nm, 449 nm, 367 nm, and 320 nm, respectively. The Raman spectral analysis revealed a noticeable shift correlating with the increasing number of halogen atoms, with intensity enhancements observed at elevated temperatures. Phonon dispersion studies corroborated the geometric stability of the optimized structures of BiOX crystals. Thermodynamic evaluations suggested that BiOX materials exhibit qualities characteristic of hard materials at higher temperatures while displaying softer material attributes at lower temperatures. In summary, this research substantially enriches the current understanding of bismuth oxyhalides by detailing their structural, electronic, optical, phonon, and thermodynamic properties. The findings presented in this study provide a foundational basis for future advancements in photocatalytic applications and material development.

Achievable dual-strategy to stabilize Li-rich layered oxide interface by a one-step wet chemical reaction towards long oxygen redox reversibility

Oxygen release and electrolyte decomposition under high voltage endlessly exacerbate interfacial ramifications and structural degradation of high energy-density Li-rich layered oxide (LLO), leading to voltage and capacity fading. Herein, the dual-strategy of CrxB complex coating and local gradient doping is simultaneously achieved on LLO surface by a one-step wet chemical reaction at room temperature. Density functional theory (DFT) calculations prove that stable B–O and Cr–O bonds through the local gradient doping can significantly reduce the high-energy O 2p states of interfacial lattice O, which is also effective for the near-surface lattice O, thus greatly stabilizing the LLO surface. Besides, differential electrochemical mass spectrometry (DEMS) indicates that the CrxB complex coating can adequately inhibit oxygen release and prevents the migration or dissolution of transition metal ions, including allowing speedy Li+ migration. The voltage and capacity fading of the modified cathode (LLO-CrB) are adequately suppressed, which are benefited from the uniformly dense cathode electrolyte interface (CEI) composed of balanced organic/inorganic composition. Therefore, the specific capacity of LLO-CrB after 200 cycles at 1C is 209.3 mA h g−1 (with a retention rate of 95.1%). This dual-strategy through a one-step wet chemical reaction is expected to be applied in the design and development of other anionic redox cathode materials.

Analytical estimate of effective charge and ground-state energies of two to five electron sequences up to atomic number 20 utilizing the variational method

BackgroundThe variational method, a quantum mechanical approach, estimates effective charge distributions and ground-state energy by minimizing the Hamiltonian's expectation value using trial wave functions with adjustable parameters. This method provides valuable insights into system behavior and is widely used in theoretical chemistry and physics. This paper aims to investigate ground-state energies and isoelectronic sequences using the variational method, introducing a novel approach for analyzing multi-electron systems. This technique allows for determining effective charge values and ground-state energies for 2–5 electrons sequence up to Z ≤ 20. Hydrogenic wave functions are used as a trial wave function to calculate effective charge in 1 s, 2 s, and 2p states. Two varying parameters were used to calculate an approximate wave function for the system. These values are then used in non-relativistic Hamiltonian with electron–electron interaction terms to calculate the ground-state energy of an atom.ResultThe results align with the reported experimental values, showing a marginal 1% error.ConclusionA Python algorithm is established based on the variational principle. It was found that, based on a few selected parameters in scripting the program, a very promising result was obtained. Furthermore, adding more variational parameters can minimize the difference between experimental and theoretical values, and this technique can be extended to elements with higher atomic numbers.

Effect of sites of doped Mg on the stability of lattice oxygen in lithium-rich manganese-based cathode materials

Elemental doping is considered as an effective method for altering the localized electronic structure of lattice oxygen in lithium-rich manganese-based oxides (LRMO) and enhancing their structural stability. However, the effect of doping heteroatoms at different sites on the oxygen redox is not clear. In this work, Mg is introduced into transition metals (TM) and lithium (Li) sites of LRMO at co-precipitation stage and lithiation stage to prepare LRMO-TM and LRMO-Li, respectively. The experimental results and density-functional theory calculations demonstrate that the oxygen release is reduced from 4.1653 nmol mg−1 of pristine to 3.3886 nmol mg−1 of LRMO-Li, and 2.7688 nmol mg−1 of LRMO-TM. The reduction of oxygen release of LRMO-Li is related to the formation of strong Mg-O interactions. Different from that, the lower oxygen release of LRMO-TM is mainly due to the reduction of electron holes in the O 2p state caused by the weaker Mn-O covalency, which effectively restricts the over-oxidization of oxygen. The capacity retention of LRMO-TM is 85.18 % at 0.2C after 200 cycles, which is higher than that of LRMO (78.63 %) and LRMO-Li (82.28 %). This work reveals the mechanism of enhancing lattice oxygen stability caused by Mg doping at different sites.

Rigid covalent organic frameworks with thiazole linkage to boost oxygen activation for photocatalytic water purification

Owing to their capability to produce reactive oxygen species (ROS) under solar irradiation, covalent organic frameworks (COFs) with pre-designable structure and unique architectures show great potentials for water purification. However, the sluggish charge separation, inefficient oxygen activation and poor structure stability in COFs restrict their practical applications to decontaminate water. Herein, via a facile one-pot synthetic strategy, we show the direct conversion of reversible imine linkage into rigid thiazole linkage can adjust the π-conjugation and local charge polarization of skeleton to boost the exciton dissociation on COFs. The rigid linkage can also improve the robustness of skeleton and the stability of COFs during the consecutive utilization process. More importantly, the thiazole linkage in COFs with optimal C 2p states (COF-S) effectively increases the activities of neighboring benzene unit to directly modulate the O2-adsorption energy barrier and improve the ROS production efficiency, resulting in the excellent photocatalytic degradation efficiency of seven toxic emerging contaminants (e.g. degrading ~99% of 5 mg L−1 paracetamol in only 7 min) and effective bacterial/algal inactivation performance. Besides, COF-S can be immobilized in continuous-flow reactor and in enlarged reactor to efficiently eliminate pollutants under natural sunlight irradiation, demonstrating the feasibility for practical application.