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In this work, we use a Bayesian optimization (BO) algorithm to sample the space of covalent organic framework (COF) components aimed at the design of COFs with a high hole conductivity. COFs are crystalline, often porous coordination polymers, where organic molecular units—called building blocks (BBs)—are connected by covalent bonds. Even though we limit ourselves here to a space of three-fold symmetric BBs forming two-dimensional COF sheets, their design space is still much too large to be sampled by traditional means through evaluating the properties of each element in this space from first principles. In order to ensure valid BBs, we use a molecular generation algorithm that, by construction, leads to rigid three-fold symmetric molecules. The BO approach then trains two distinct surrogate models for two conductivity properties, level alignment vs a reference electrode and reorganization free energy, which are combined in a fitness function as the objective that evaluates BBs' conductivities. These continuously improving surrogates allow the prediction of a material's properties at a low computational cost. It thus allows us to select promising candidates which, together with candidates that are very different from the molecules already sampled, form the updated training sets of the surrogate models. In the course of 20 such training steps, we find a number of promising candidates, some being only variations on already known motifs and others being completely novel. Finally, we subject the six best such candidates to a computational reverse synthesis analysis to gauge their real-world synthesizability. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride (h-BN) has excellent thermal conductivity and dielectric properties, which shows great potential for low-dimensional devices. However, mechanical properties of h-BN have not been comprehensively investigated through experiments. In this work, we conduct in situ direct tensile tests on freestanding single-crystal few-layer h-BN nanosheets with various layer numbers from 3 to 8, with an elaborate sample transfer and characterization protocol. Young's modulus of 573.8 ± 101.4 GPa and a tensile fracture strain up to 3.2% are revealed, which are comparable to its monolayer counterpart. Moreover, we find a tough-to-brittle transition in few-layer h-BN with the increase in layer number, which is attributed the interplay between the van der Waals interaction and in-plane covalent bonding. These findings could open up new possibilities in mechanical research of van der Waals materials and provide guidance for the design of h-BN-based devices and composites. [ABSTRACT FROM AUTHOR]

Hydrogen is a promising energy carrier, but its onboard application is limited by the need for compact, low-pressure storage solutions. Solid-state complex metal hydride systems, such as MgB 2 /Mg(BH 4) 2 , offer high storage capacities but suffer from sluggish kinetics and poor reversibility. One avenue for improving reactivity is to introduce metal dopants to alter electronic and atomic properties, but the role of these chemical additives remains poorly understood, particularly for the hydrogenation reaction. In this work, we used density functional theory calculations on model MgB 2 systems to rationalize the potential role of metal dopants in destabilizing B–B bonding within the MgB 2 lattice. We carried out detailed electronic structure analyses for 28 different metal dopant adatoms to identify properties that contribute to a dopant's efficacy. Based on the simulation results, we propose that an intermediate ionic and covalent character of the bonds between adatoms and B atoms is desirable for facilitating charge redistribution, disrupting the B–B bond network, and promoting H 2 dissociation and H atom chemisorption on MgB 2. [ABSTRACT FROM AUTHOR]

Endohedral metal–metal-bonding fullerenes have recently emerged, in which encapsulated metals form a metal–metal bond. However, the physical reasons why some metal elements prefer to form metal–metal bonds inside fullerene are still unclear. Herein, we reported first-principles calculations on electronic structures, bonding properties, dynamics, and thermodynamic stabilities of endohedral metallofullerenes M2@C82 (M = Sc, Y, La, Lu). Multiple bonding analysis approaches unambiguously reveal the existence of one two-center two-electron σ covalent metal–metal bond in M2@C82 (M = Sc, Y, Lu); however, the La–La bonding interaction in La2@C82 is weaker and could not be categorized as one metal–metal covalent bond. The energy decomposition analysis on bonding interactions between an encapsulated metal dimer and fullerene cages suggested that there exist two electron-sharing bonds between a metal dimer and fullerene cages. The reasons why La2 prefers to donate electrons to fullerene cages rather than form a standard σ covalent metal–metal bond are mainly attributed to two following facts: La2 has a lower ionization potential, while the hybridization of ns, (n − 1)d, and np atomic orbitals in La2 is higher. Ab initio molecular dynamic simulations reveal that the M–M bond length at room temperature follows the trend of Sc < Lu < Y. The statistical thermodynamics calculations at different temperatures reveal that the experimentally observed endohedral metal–metal-bonding fullerenes M2@C82 have high concentrations in the endohedral fullerene formation temperature range. [ABSTRACT FROM AUTHOR]

Ovonic threshold switching (OTS) selectors play a critical role in suppressing the sneak-path current of three-dimensional crossbar integration circuits. Compared to conventional nonmetal-telluride OTS selectors, selectors based on AlxTey glass are found to have both satisfactory on-state current and selectivity. However, it is unclear why the Al-rich AlxTey glass-based OTS selectors have robust insulation properties for reducing the off-state current. This work reveals the structure–property correlations of amorphous AlxTey at the atomic scale by first-principles calculations. It is found that the stoichiometric Al2Te3 glass tends to have a clean bandgap owing to the covalent and dative bonds formed by non-equivalent sp3-hybridized Al orbitals and the lone-pair electrons of Te. Unexpectedly, for Al-rich AlxTey glass (Al2.21Te2.79), the Al–Al bonds formed by redundant Al-atoms have an integrated crystal orbital bond index (ICOBI) of 0.8–0.9, which is much larger than that of Al–Al bonds in pure metals (0.227), indicating they are covalent. It is the covalent Al–Al bonds that ensure the robust insulation characteristics of Al-rich AlxTey glass, while the Te–Te interaction in the Al-poor AlxTey glass (Al1.79Te3.21) produces midgap states, thereby reducing the insulativity. The presented atomic and electronic pictures here will provide useful theoretical insights for designing OTS selectors with improved performances. [ABSTRACT FROM AUTHOR]

Strong and weak interatomic interactions in chemical and biological systems are ubiquitous, yet how to identify them on a unified theoretical foundation is still not well established. Recently, we proposed employing Pauli energy-based indexes, such as strong covalent interaction and bonding and noncovalent interaction indexes, in the framework of density functional theory for the purpose. In this work, we extend our previous theoretical work by directly employing Pauli energy, Pauli potential, Pauli force, and Pauli charge to simultaneously identify both strong covalent bonding and weak noncovalent interactions. Our results from this work elucidate that using their signature isosurfaces, we can identify different types of interactions, either strong or weak, including single, double, triple, and quadruple covalent bonds, ionic bond, metallic bond, hydrogen bonding, and van der Waals interaction. We also discovered strong linear correlations between Pauli energy derived quantities and different covalent bond orders. These qualitative and quantitative results from our present study solidify the viewpoint that a unified approach to simultaneously identify both strong and weak interactions is possible. In our view, this work signifies one step forward towards the goal of establishing a density-based theory of chemical reactivity in density functional theory. [ABSTRACT FROM AUTHOR]

Interlayers between a substrate and a functional film are used extensively to tailor film adhesion and avoid failure induced by delamination. With nitrogen doping increasingly used to improve the surface properties of steel, how to select appropriate interlayers for high film adhesion on substrate remains elusive in theory. Using spin-polarized density functional theory computations, the authors investigated the effects of N doping on the mechanical properties of Fe and its adhesion with widely used Cr, Ti, and Si interlayers. The results showed that N atoms doped at the Fe octahedron center increased hardness by 30% under 4 wt. % N. N atom at Cr/Fe, Ti/Fe, Si/Fe interfaces interestingly increased the interlayer adhesion of Ti/Fe and Si/Fe, while reducing that of Cr/Fe. This behavior is attributed to competition between magnetic coupling and atomic bonding. For Cr/Fe with strong magnetic coupling, the reduction in adhesion was resulted from doped N that inhibited magnetic coupling at the interface. For Ti/Fe and Si/Fe with weak magnetic coupling, the formation of covalent bonds at the interface by the N atom increased interfacial adhesion. This study provides insights into the nitrogen doping of steel and the selection of proper interlayers for strong film-substrate adhesion. [ABSTRACT FROM AUTHOR]

Proton transport in aqueous systems occurs by making and breaking covalent bonds, a process that classical force fields cannot reproduce. Various attempts have been made to remedy this deficiency, by valence bond theory or instantaneous proton transfers, but the ability of such methods to provide a realistic picture of this fundamental process has not been fully evaluated. Here we compare an ab initio molecular dynamics (AIMD) simulation of an excess proton in water to a simulation of a classical H3O+ in TIP3P water. The energy gap upon instantaneous proton transfer from H3O+ to an acceptor water molecule is much higher in the classical simulation than in the AIMD configurations evaluated with the same classical potential. The origins of this discrepancy are identified by comparing the solvent structures around the excess proton in the two systems. One major structural difference is in the tilt angle of the water molecules that accept an hydrogen bond from H3O+. The lack of lone pairs in TIP3P produces a tilt angle that is too large and generates an unfavorable geometry after instantaneous proton transfer. This problem can be alleviated by the use of TIP5P, which gives a tilt angle much closer to the AIMD result. Another important factor that raises the energy gap is the different optimal distance in water-water vs H3O+-water H-bonds. In AIMD the acceptor is gradually polarized and takes a hydronium-like configuration even before proton transfer actually happens. Ways to remedy some of these problems in classical simulations are discussed. [ABSTRACT FROM AUTHOR]

First-principles calculations are performed, revealing a significant enhancement of the piezoelectric properties of wurtzite Zn 3 6 O 3 6 upon the incorporation of a single Cu atom. Research has demonstrated that the piezoelectric constant d 3 3 reaches its maximum value at a doping concentration of 1.4% for Cu atoms. The lattice parameters a and c of Zn 3 6 O 3 6 are decreased and the piezoelectric strain coefficient d 3 3 is increased by replacing one Cu atom in Zn 3 6 O 3 6 . It is found that elastic softening is the primary factor responsible for the increase of d 3 3 in Zn 3 5 Cu1O 3 6 . By differential charge density analysis, it is found that the covalency between Cu–O bonds is lower than that of Zn–O bonds, and the covalent bonding characteristics are weakened. Bader charge analysis shows that the charge of Cu is higher than that of Zn, indicating a more significant ionic bonding feature than that of Zn. Thus, a weaker covalent and stronger ionic bond are considered to play an essential role in promoting elastic softening for ZnO, which eventually promotes a significant enhancement in piezoelectric properties. [ABSTRACT FROM AUTHOR]

Herein, inspired by the macrophage's defensive behavior of releasing free radicals to kill bacteria and viruses, a marine antifouling coating with dynamic surfaces is prepared by precise regulation of dynamic covalent bonds. Alkyl radical (R·) derived from oxime-urethane structure attracts and disrupts microbe cell membrane and pili between intimate cells, resulting in excellent anti-biofouling effect. Moreover, the newly exposed coating then continues to break, which ultimately results in the peeling of the layers, thus making barnacles, mussels and other fouling organisms less likely to adhere. [Display omitted] • Macrophage-inspired marine antifouling coating with dynamic surfaces is prepared. • Alkyl radical (R·) derived from oxime-urethane structure offers excellent anti-fouling performance. • The newly exposed coating continues to break making it less likely that fouling organisms will adhere to it. • This study presents a novel methodology for fulfilling the technological gap of marine coatings with dynamic surface. Macrophages can kill bacteria and viruses by releasing free radicals, which provides a possible approach to construct antifouling coatings with dynamic surfaces that release free radicals if the breaking of dynamic covalent bonds is precisely regulated. Herein, inspired by the defensive behavior of macrophages of releasing free radicals to kill bacteria and viruses, a marine antifouling coating composed of polyurethane incorporating dimethylglyoxime (PU x -DMG) is prepared by precise regulation of dynamic oxime-urethane covalent bonds. The obtained alkyl radical (R·) derived from the cleavage of the oxime-urethane bonds manages to effectively suppress the attachment of marine biofouling. Moreover, the intrinsic dynamic surface makes it difficult for biofouling to adhere and ultimately achieves sustainable antifouling property. Notably, the PU 50 -DMG coating not only presents efficient antibacterial and antialgae properties, but also prevents macroorganisms from settling in the sea for up to 4 months. This provides a pioneer broad-spectrum strategy to explore the marine antifouling coatings. [ABSTRACT FROM AUTHOR]

Three‐dimensional graphene architecture (3DGA) as reinforcement with successive reinforcement effect has attracted intense attention in the field of polymer composites, while 3DGA also faces the disadvantages of weak interfacial adhesion with matrices. The surface decoration of 3DGA with molybdenum disulfide (3DGA@MoS2) further promoted the diffusion and penetration of epoxy molecular for 3DGA network with the aid of resin transfer molding (RTM) technic. The MoS2 transition nanolayer not only forms covalent bonding with 3DGA but mechanical interlocks with epoxy, which effectively improved the interface combination in composite. Compared with neat epoxy, the glass transition temperature (Tg) and tensile strength increased by 18°C and 58.6%, as well as the average friction coefficient and wear rate decreased by 84% and 89%, respectively, by low loading of only 2 wt% 3DGA@MoS2. Hence, the 3D graphene modified strategy by surface decoration provides a new insight for manufacturing high‐performance epoxy‐graphene composites with excellent tribological properties. Highlights: A highly ordered and interconnected 3DGA reinforcement was fabricated.MoS2 serves as interlayer, forming covalent bond and mechanical interlock.Incorporation of 3DGA@MoS2 enables rapid heat conduction and load transfer.Bi‐interpenetrating 3D structure/polymer network endows good wear resistance.Improved comprehensive properties ascribe to strong interface adhesion. [ABSTRACT FROM AUTHOR]

Polysulfides are significant compounds in life science, pharmaceutical science, and materials science. Therefore, polysulfide construction is in great demand. The controllable sequential installation of groups on both ends of a S−S motif faces an enormous challenge owing to the reversible nature of the covalent S−S bond. A library was established with two divergent mask groups for bilateral unsymmetrical disulfurating reagents (R1O−SS−SO2R2). Sequential coupling with preferential activation of the S−SO2 bond (37.6 kcal/mol) and controllable activation of the S−O bond (54.8 kcal/mol) in the presence of the S−S bond (62.0 kcal/mol) enabled successive reactions at each end of the S−S motif to afford unsymmetrical disulfides and trisulfides, even for the cross‐linkage of natural products, pharmaceuticals, peptides, and a protein (bovine serum albumin). [ABSTRACT FROM AUTHOR]

Highly conductive Ti3C2Tx pseudo‐capacitors hold promise to expand energy density by utilizing ionic liquid (IL) electrolytes (e.g., 1‐ethyl‐3‐methylimidazolium bis trifluoromethane sulfonyl imide, EMITFSI) that possesses broaden voltage window, resulting in various applications involving hybrid vehicle, rail transportation, and power system. However, abundantly random surface ‒OH terminations cannot maintain an extremely stabilized Ti3C2Tx layer spacing framework for efficient ion arrangements, increase ionic diffusion barriers, and decline in energy density. Herein, intensely chemical covalent bonding interactions of ‒SH, ‒COOH, and ‒NH2 terminated L‐cysteine molecules with ‒OH terminations are proposed to stabilize Ti3C2Tx and expand interlayer structure, allowing sufficient ionic transport and realizing high energy‐density Ti3C2Tx pseudo‐capacitors. It is found that, with cysteine molecules stayed flat to Ti3C2Tx layer, superior hydrophilic surface, and increased interlayer spacing to 1.51 nm, 2.16‐folds higher than Ti3C2Tx electrode, the Ti3C2Tx‒cysteine electrode delivered high capacitance of 279 F g−1 in EMITFSI/acetonitrile electrolyte. Assembled asymmetric Ti3C2Tx‒cysteine//activated carbon flexible device exhibited a high voltage of 2.9 V and a high energy density of 72.1 Wh kg−1 at a power density of 874 W kg−1, which could power various colored smart rollable flexible electronics at bent angle of 90°. Additionally, identical mechanisms are found in Ti3C2Tx‐amino acid systems, wherein amino acid stayed flat between Ti3C2Tx layers with optimized content, interlayer spacing, and capacitance, no matter amino acid in different charged feature and different sidechain lengths (e.g., glutamine, cysteine, and lysine). The present study provides systematically experimental evidence for improving ion accessibility in IL electrolytes based on an organic‐modified Ti3C2Tx electrode structure. [ABSTRACT FROM AUTHOR]

Transitioning towards a circular economy, extensive research has focused on dynamic covalent bonds (DCBs) to pave the way for more sustainable materials. These bonds enable debonding and rebonding on demand, as well as facilitating end‐of‐life recycling. Acylhydrazone/hydrazone chemistry offers a material with high stability under neutral and basic conditions making it a promising candidate for materials research, though the material is susceptible to acid degradation. However, this degradation under acidic conditions can be exploited, making it widely applicable in self‐healing and biomedical fields, with potential for reprocessing and recycling. This review highlights studies exploring the reversibility of acylhydrazone/hydrazone bonds in various polymers, altering their properties, and utilizing them in applications such as self‐healing, reprocessing, and recycling. The review also focuses on how the mechanical properties are affected by the presence of dynamic linkages, and methods to improve the mechanical performance. [ABSTRACT FROM AUTHOR]

Primary amines, in the form of unmodified N‐terminus of peptide/protein and unmodified lysine residue, are perhaps the most important functional groups that can serve as the starting points in proteomic analysis, especially via mass spectrometry‐based approaches. A variety of multifunctional probes that conjugate primary amine groups through covalent bonds have been developed and employed to facilitate protein/protein complex characterization, including identification, quantification, structure and localization elucidation, protein–protein interaction investigation, and so forth. As an integral part of more accurate peptide quantification in targeted proteomics, isobaric stable isotope‐coded primary amine labeling approaches eventually facilitated protein/peptide characterization at the single‐cell level, paving the way for single‐cell proteomics. The development and advances in the field can be reviewed in terms of key components of a multifunctional probe: functional groups and chemistry for primary amine conjugation; hetero‐bifunctional moiety for separation/enrichment of conjugated protein/protein complex; and functionalized linker/spacer. Perspectives are primarily focused on optimizing primary amine conjugation under physiological conditions to improve characterization of native proteins, especially those associated with the surface of living cells/microorganisms. [ABSTRACT FROM AUTHOR]

Electrocatalytic conversion of CO2 into formate is recognized an economically‐viable route to upgrade CO2, but requires high overpotential to realize the high selectivity owing to high energy barrier for driving the involved proton‐coupled electron transfer (PCET) processes and serious ignorance of the second PCET. Herein, we surmount the challenge through sequential regulation of the potential‐determining step (PDS) over Te‐doped Bi (TeBi) nanotips. Computational studies unravel the incorporation of Te heteroatoms alters the PDS from the first PCET to the second one by substantially lowering the formation barrier for *OCHO intermediate, and the high‐curvature nanotips induce enhanced electric field that can steer the formation of asymmetric *HCOOH. In this scenario, the thermodynamic barrier for *OCHO and *HCOOH can be sequentially decreased, thus enabling a high formate selectivity at low overpotential. Experimentally, distinct TeBi nanostructures are obtained via controlling Te content in the precursor and TeBi nanotips achieve >90 % of Faradaic efficiency for formate production over a comparatively positive potential window (−0.57 V to −1.08 V). The strong Bi−Te covalent bonds also afford a robust stability. In an optimized membrane electrode assembly device, the formate production rate at 3.2 V reaches 10.1 mmol h−1 cm−2, demonstrating great potential for practical application. [ABSTRACT FROM AUTHOR]

Summary: In order to improve the adsorption properties and stability of porous starch, the porous starch made from ground rice starch was doubly modified by cross‐linking and esterification using sodium trimetaphosphate (STMP) as a cross‐linking agent and octenyl succinic anhydride (OSA) as an esterifying agent. Structural analysis of the samples showed that the phosphate group in STMP formed a new P‐O‐C covalent bond with the hydroxyl group in starch by substitution, OSA combined with the hydroxyl group of starch formed an ester carbonyl group, and all cross‐linking and esterification occurred in the amorphous region of starch. DSC and TG/DTG analysis showed that STMP modification performed better than OSA modification in thermal stability. However, by analysis of the oil absorption properties and freeze–thaw stability, the OSA‐modified porous starch exhibited better oil‐holding rate and freeze–thaw stability. [ABSTRACT FROM AUTHOR]

Dimensional regulation in polyoxometalates is an effective strategy during the design and synthesis of polyoxometalates-based high proton conductors, but it is not available to date. Herein, the precise regulation of dimensionality has been realized in an unprecedented gigantic molybdenum blue wheel family featuring pentagonal {(W)Mo5} motifs through optimizing the molar ratio of Mo/W, including [Gd2Mo124W14O422(H2O)62]38− (0D-{Mo124W14}, 1), [Mo126W14O441(H2O)51]70− (1D-{Mo126W14}n, 2), and [Mo124W14O430(H2O)50]60− (2D-{Mo124W14}n, 3). Such important {(W)Mo5} structural motif brings new reactivity into gigantic Mo blue wheels. There are different numbers and sites of {Mo2} defects in each wheel-shaped monomer in 1–3, which leads to the monomers of 2 and 3 to form 1D and 2D architectures via Mo–O–Mo covalent bonds driven by {Mo2}-mediated H2O ligands substitution process, respectively, thus achieving the controllable dimensional regulation. As expected, the proton conductivity of 3 is 10 times higher than that of 1 and 1.7 times higher than that of 2. The continuous proton hopping sites in 2D network are responsible for the enhanced proton conductivity with lower activation energy. This study highlights that this dimensional regulation approach remains great potential in preparing polyoxometalates-based high proton conductive materials. [ABSTRACT FROM AUTHOR]

Si is an important semiconductor material in the development of modern industry. With the miniaturization trend of semiconductor devices, the size of Si has reached the cluster size. The search for stable Si clusters is an important issue. In this work, the electronic structures and stability mechanism of the W@Si12 cluster are calculated by the first-principle calculations. Different from a C2v hexacapped trigonal prism structure of Si12, the W@Si12 cluster presents an embedded hexagonal prism structure with D6h symmetry. The addition of W atom leads to a higher stability. The molecular orbitals show obvious superatomic characteristics for the W@Si12 cluster, and their energy levels are more degenerate than that of the Si12 cluster. The population analysis indicates that a total charge of 2.21e is transferred from Si atoms to the center W atom, which suggests an ionic bond for W-Si. The electron localization function further proves a covalent bond for Si–Si. The enhanced stability of the W@Si12 cluster is attributed to the combination of the ionic and covalent bonds. [ABSTRACT FROM AUTHOR]

Antibiotic‐loaded polymethylmethacrylate (PMMA) beads are commonly employed to treat prosthetic joint infections (PJI) and chronic osteomyelitis due to their excellent mechanical strength. However, PMMA's non‐degradability results in a burst release of antibiotics and potential renal toxicity, necessitating additional surgeries for bead removal. There is a critical need for infection control materials that can deliver antibiotics effectively, maintain adequate mechanical strength, and degrade uniformly. This study introduces a gelatin–silica hybrid antibiotic carrier, characterized by covalent bonds between the gelatin and silica networks. The incorporation of the silica network enhances the compressive strength to 32.53 ± 2.4 MPa and ensures uniform degradation over 6 months, aligning with clinical timelines. Furthermore, the gelatin–silica hybrid can support up to 10 wt% antibiotic loading without compromising its properties, making it a promising candidate for next‐generation infection control materials. [ABSTRACT FROM AUTHOR]

A cationic copper‐stabilized coppoborylene was prepared and structurally characterized via infrared photodissociation spectroscopy and density functional theory calculations. This structure exemplifies a new class of borylenes stabilized by three‐center‐two‐electron metal‐boron‐metal covalent bonding interaction, displaying exceptional σ‐acidity and unparalleled π‐donor capability for CO activation that outperforms all of the known transition metal cations and is comparable or even superior to the documented base‐trapped borylenes. Its neutral form represents a monovalent boron compound with a strongly reactive amphoteric boron center built on transition‐metal‐boron bonds, which inspires the design and synthesis of new members of the borylene family. [ABSTRACT FROM AUTHOR]

Supramolecular mechanophores typically exhibit much lower mechanical strengths than covalent counterparts, with strengths usually around 100 pN, which is significantly lower than the nN‐scale strength of covalent bonds. Inspired by the slow dissociation kinetics of the cucurbit[7]uril (CB[7])–hexanoate‐isoquinoline (HIQ) complex, we discovered that charge–dipole repulsion can be utilized to create strong supramolecular mechanophores. When activated at its −COO− state, the CB[7]−HIQ complex exhibits a high mechanical strength of ~700 pN, comparable to weak covalent bonds such as Au−S bonds or thiol–maleimide adducts. The strength of the CB[7]−HIQ complex can also be tuned with pH in a gradual manner, with a minimum value of ~150 pN at its −COOH state, similar to an ordinary supramolecular conjugate. This research may pave the way for the development of supramolecular architectures that combine the advantages of covalent and supramolecular systems. [ABSTRACT FROM AUTHOR]

Studies of graphene show that robust chemical bonds such as covalent bonds with trigonal‐planar atoms afford layered atomic 2D crystals possessing unique properties. Although layered molecular crystals are of interest to diversify elements and structures of 2D materials, the structural diversity of molecules as well as weak intermolecular interactions inevitably makes the design to be one‐off and individual. We herein report a versatile method to assemble layered molecular crystals. By developing a D3‐symmetry host at vertices to form a honeycomb layer, a diverse range of layered 2D host–guest crystals were obtained. Substituents on the host, elements/structures of the guest, the stereochemistry of the host and types of intercalants were diversified, which should allow for 6×32×3×2 combinations for structural diversification. [ABSTRACT FROM AUTHOR]

Self-healing covalent adaptable networks (CANs) are not only of fundamental interest but also of practical importance for achieving carbon neutrality and sustainable development. However, there is a trade-off between the mobility and cross-linking structure of CANs, making it challenging to develop CANs with excellent mechanical properties and high self-healing efficiency. Here, we report the utilization of a highly dynamic four-arm cross-linking unit with an internally catalyzed oxime-urethane group to obtain CAN-based ionogel with both high self-healing efficiency (>92.1%) at room temperature and superior mechanical properties (tensile strength 4.55 MPa and toughness 13.49 MJ m-3). This work demonstrates the significant potential of utilizing the synergistic electronic, spatial, and topological effects as a design strategy for developing high-performance materials. [ABSTRACT FROM AUTHOR]

In this contribution, a novel binuclear heteroleptic complex [Pb2L2(CO3)]·2CH3CN·2MeOH (1·2CH3CN·2MeOH) is reported, which was fabricated by electrochemical oxidation of a lead anode under an ambient atmosphere in a CH3CN : MeOH solution of N′-isonicotinoylpyrazine-2-carbohydrazonamide (HL). The CO32− anion was produced from the conversion of aerial CO2 by the Pb2+–L complex system under electrochemical conditions. In the structure of 1, ligand L exhibits a tridentate pincer-like N,N′,O-coordination mode, while the CO32− anion exhibits a tetradentate bridging coordination mode with one of the oxygen atoms exhibiting a bridging μ-coordination mode. The metal cations in the structure of 1 are in a five-membered N2O3 coordination environment, formed by covalent bonds. The molecular structure of 1·2CH3CN·2MeOH is stabilized by a pair of intermolecular Pb⋯N tetrel bonds formed with one of the NH2 nitrogen atoms of an adjacent complex molecule and with the acetonitrile nitrogen atom, and one Pb⋯O tetrel bond formed with the carbonyl oxygen atom of the other adjacent complex molecule, yielding a 2D supramolecular sheet. This sheet is further stabilized by intermolecular N–H⋯Nacetonitrile and N–H⋯Ocarbonate hydrogen bonds and πPyrazine⋯πPyridine interactions. The optical properties of the complex were revealed by UV-vis spectroscopy and spectrofluorimetry in MeOH. It was established that the described complex is emissive upon excitation at 340 nm with a broad band from about 500 nm to 780 nm with a maximum at ∼580 nm, accompanied by a shoulder at ∼620 nm. The CIE-1931 chromaticity coordinates of (0.28, 0.36) fall within the white gamut of the chromaticity diagram. Thus, complex 1 is a single-component white light-emitting phosphor. [ABSTRACT FROM AUTHOR]

The interaction of H, H2, and MgH2 with graphene is investigated using the density functional theory to explore the possibility of exploiting graphene or functionalized graphene as a hydrogen storage medium. The H atom is positioned at various distances from the graphene surface and the energetics are computed in detail. The extent of interaction of the s electron of H with graphene's pz electrons is well brought out. Similar investigations are carried out for H2, MgH2. In the case of H atom, a HC covalent bond is formed. This process turns out to be a prerequisite for proton transfer through graphene. Interactions of H2 and MgH2 with graphene are different from that of H. It leads to the conclusion that functionalized graphene will better substrate/candidate for applications like hydrogen storage. [ABSTRACT FROM AUTHOR]

Metal oxides containing La, Mn, and Co cations can catalyze oxygen reduction reactions (ORRs) in electrochemical processes. However, these materials require carbon support and optimal interactions between both compounds to be active. In this work, two approaches to prepare composites of La-Mn-Co-based compounds over carbon xerogel were developed. Using sol-gel methods, either the metal-based material was deposited on the existing carbon xerogel or vice versa. The metal oxide selected was the LaMn0.7Co0.3O3 perovskite, which has good catalytic behavior and selectivity towards direct ORRs. All the as-prepared composites were tested for ORRs in alkaline liquid electrolytes and characterized by diverse physicochemical techniques such as XRD, XPS, SEM, or N2 adsorption. Although the perovskite structure either decomposed or failed to form using those in situ methods, the materials exhibited great catalytic activity, which can be ascribed to the strengthening of the interactions between oxides and the carbon support via C-O-M covalent bonds and to the formation of new active sites such as the MnO/Co heterointerfaces. Moreover, Co-Nx-C species are formed during the synthesis of the metal compounds over the carbon xerogel. These species possess a strong catalytic activity towards ORR. Therefore, the composites formed by synthesizing metal compounds over the carbon xerogel exhibit the best performance in the ORR, which can be ascribed to the presence of the MnO/Co heterointerfaces and Co-Nx-C species and the strong interactions between both compounds. Moreover, the small nanoparticle size leads to a higher number of active sites available for the reaction. [ABSTRACT FROM AUTHOR]

Exfoliated graphite (ExG) embedded in a polymeric matrix represents an accessible, cost-effective, and sustainable method for generating nanosized graphite-based polymer composites with multifunctional properties. This review article analyzes diverse methods currently used to exfoliate graphite into graphite nanoplatelets, few-layer graphene, and polymer-assisted graphene. It also explores engineered methods for small-scale pilot production of polymer nanocomposites. It highlights the chemistry involved during the graphite intercalation and exfoliation process, particularly emphasizing the interfacial interactions related to steric repulsion forces, van der Waals forces, hydrogen bonds, π-π stacking, and covalent bonds. These interactions promote the dispersion and stabilization of the graphite derivative structures in polymeric matrices. Finally, it compares the enhanced properties of nanocomposites, such as increased thermal and electrical conductivity and electromagnetic interference (EMI) shielding applications, with those of neat polymer materials. [ABSTRACT FROM AUTHOR]

The Zn─Sb binary system contains two high‐performing thermoelectric materials, namely the ordered ZnSb and the disordered Zn13Sb10. Both systems exhibit low thermal conductivity, which is speculated to originate from multicentre bonding within Zn2Sb2‐rhombi. Here, the electron density of ZnSb is reported based on multipole modelling of accurate X‐ray diffraction data measured at 20 K. Topological analysis reveals that the bond paths in the rhombus are endocyclically strained and that electron density is concentrated within the rhombus rather than along its geometric bonds consistent with a multicentre bond description. However, the electron density is not equally shared between the geometric bonds of the rhombus. Electron density analysis and modelling of low‐temperature anharmonicity reveal that one Zn–Sb interaction is weaker than the other. Taken together with the orientation of bonds external to the rhombus structure, an alternative description emerges wherein the multicentre bond is more partially localised along one set of the opposite legs of the rhombus. In this description, the stronger bond can be considered a traditional 2‐centre‐2‐electron bond, while the weaker interaction is coordinative to the covalent bond. The anharmonicity and low thermal conductivity may consequently be understood as Zn rattling along the coordinative interaction. [ABSTRACT FROM AUTHOR]

Achieving a harmonious balance between strength and plasticity is a long-standing problem in single-phase face-centered-cubic (fcc) high-entropy alloys (HEAs). Herein, in-situ TiC ceramic particle reinforced fcc-structured Fe 1.4 Co 0.8 Ni 0.8 Cr HEAs is designed and investigated by combining the experiments and first-principate calculations. The results show that the y (TiC)–Fe 1.4 Co 0.8 Ni 0.8 Cr (y = 0, 2.5, 5.0, 7.5 and 10.0 %, y: volume fraction) composites consist of fcc phase with submicron/micron TiC after the co-addition of Ti and C element, and the formation of TiC facilitates to refine the microstructure of the composites. Such microstructural evolutions significantly enhance the mechanical performances of the composites. Particularly, the 7.5 % (TiC)–Fe 1.4 Co 0.8 Ni 0.8 Cr composite exhibits a high yield strength of ∼562.7 ± 7.7 MPa and tensile strength of ∼971.3 ± 5.4 MPa, which are respectively increased by 169.0 % and 88.3 % as compared with the Fe 1.4 Co 0.8 Ni 0.8 Cr based alloy, yet with the fracture elongation decreases to 35.9 ± 0.3 %. The increment in yield strength is mainly driven from the combined effect of the grain refinement strengthening, dislocation strengthening and precipitation strengthening. Density functional theory (DFT) results reveal that the increase of C –Ti bonds and the formation of covalent bonds in the 7.5 % (TiC)–Fe 1.4 Co 0.8 Ni 0.8 Cr composite lead to relatively higher strength and lower ductility, which are well agreed with the experimental results. [ABSTRACT FROM AUTHOR]

Supramolecular assembly frameworks (SAFs) represent a new category of porous materials, utilizing non‐covalent interactions, setting them apart from metal–organic frameworks (MOFs) and covalent organic frameworks (COFs). This category includes but is not restricted to hydrogen‐bonded organic frameworks and supramolecular organic frameworks. SAFs stand out for their outstanding porosity, crystallinity, and stability, alongside unique dissolution‐recrystallization dynamics that enable significant structural and functional modifications. Crucially, their non‐covalent assembly strategies allow for a balanced manipulation of porosity, symmetry, crystallinity, and dimensions, facilitating the creation of advanced crystalline porous materials unattainable through conventional covalent or coordination bond synthesis. Despite their considerable promise in overcoming several limitations inherent to MOFs and COFs, particularly in terms of solution‐processability, SAFs have received relatively little attention in recent literature. This Minireview aims to shed light on standout SAFs, exploring their design principles, synthesis strategies, and characterization methods. It emphasizes their distinctive features and the broad spectrum of potential applications across various domains, aiming to catalyze further development and practical application within the scientific community. [ABSTRACT FROM AUTHOR]

Covalent adaptable networks (CANs), leveraging the dynamic exchange of covalent bonds, emerge as a promising material to address the challenge of irreversible cross‐linking in thermosetting polymers. In this work, we explore the introduction of a catalyst‐free and associative C=C/C=N metathesis reaction into thermosetting polyurethanes, creating CANs with superior stability, solvent resistance, and thermal/mechanical properties. By incorporating this dynamic exchange reaction, stress‐relaxation is significantly accelerated compared to imine‐bond‐only networks, with the rate adjustable by modifying substituents in the ortho position of the dynamic double bonds. The obtained plasticity enables recycle without altering the chemical structure or mechanical properties, and is also found to be vital for achieving shape memory functions with complex spatial structures. This metathesis reaction as a new dynamic crosslinker of polymer networks has the potential to accelerate the ongoing exploration of malleable and functional thermoset polymers. [ABSTRACT FROM AUTHOR]

Reductive elimination is a key step in Ni-catalysed cross-couplings, which is often considered to result in new covalent bonds. Due to the weak oxidizing ability of Ni(II) species, reductive eliminations from Ni(II) centers are challenging. A thorough mechanistic understanding of this process could inspire the rational design of Ni-catalysed coupling reactions. In this article, we give an overview of recent advances in the mechanistic study of reductive elimination from Ni(II) species achieved by our group. Three possible models for reductive elimination from Ni(II) species were investigated and discussed, including direct reductive elimination, electron density-controlled reductive elimination, and oxidation-induced reductive elimination. Notably, the direct reductive elimination from Ni(II) species often requires a high activation energy in some cases. In contrast, the electron density-controlled and oxidation-induced reductive elimination pathways can significantly enhance the driving force for reductive elimination, accelerating the formation of new covalent bonds. The intricate reaction mechanisms for each of these pathways are thoroughly discussed and systematically summarized in this paper. These computational studies showcase the characteristics of three models for reductive elimination from Ni(II) species, and we hope that it will spur the development of mechanistic studies of cross-coupling reactions. [ABSTRACT FROM AUTHOR]

Microflow catalysis is a cutting-edge approach to advancing chemical synthesis and manufacturing, but the challenge lies in developing efficient and stable multiphase catalysts. Here we showcase incorporating amine-containing metal-organic cages into automated microfluidic reactors through covalent bonds, enabling highly continuous flow catalysis. Two Fe4L4 tetrahedral cages bearing four uncoordinated amines were designed and synthesized. Post-synthetic modifications of the amine groups with 3-isocyanatopropyltriethoxysilane, introducing silane chains immobilized on the inner walls of the microfluidic reactor. The immobilized cages prove highly efficient for the reaction of anthranilamide with aldehydes, showing superior reactivity and recyclability relative to free cages. This superiority arises from the large cavity, facilitating substrate accommodation and conversion, a high mass transfer rate and stable covalent bonds between cage and microreactor. This study exemplifies the synergy of cages with microreactor technology, highlighting the benefits of heterogenous cages and the potential for future automated synthesis processes Microflow catalysis represents a cutting-edge method for advancing chemical synthesis and manufacturing, though developing efficient and stable multiphase catalysts remains challenging. Here the authors demonstrate the incorporation of amine-containing metal-organic cages into automated microfluidic reactors through covalent bonds, facilitating highly continuous flow catalysis. [ABSTRACT FROM AUTHOR]

Herein, radio frequency (RF) Joule heating is used to trigger dynamic covalent bond exchange in a furan‐maleimide Diels–Alder polymer (DAP). Prior work shows that carbon susceptors can be incorporated into materials and undergo Joule heating when exposed to an electric field. Herein, carbon nanotubes (CNTs) are added to the DAP to make the material responsive to RF fields, and to enable selective, noncontact healing behavior of DAP after electric field exposure. After healing, mechanical testing is conducted to compare the tensile strength and toughness of the healed samples with the mechanical properties of the original, undamaged samples. A 96.2% recovery in tensile strength and an 83.2% recovery in toughness are observed. Also, RF heating of DAP/CNT enables repeated bonding and debonding of the material, allowing for adhesion and deadhesion on demand. [ABSTRACT FROM AUTHOR]

The commercial application of lithium‐rich layered oxides still has many obstacles since the oxygen in Li2MnO3 has an unstable coordination and tends to be released when Li‐ion is extracted at the voltage higher than 4.5 V. In this work, a series of cobalt‐free lithium‐rich manganese‐based oxide cathodes (Li1+xTM1‐xO2, TM = Mn, Ni) are synthesized by gradually decreasing the Li/TM ratio. Among these cobalt‐free Li‐rich manganese‐based oxides (LRMO), LR‐1.2 (when Li/TM = 1.2) has an optimized dual‐phase (namely Li2MnO3 and LiTMO2‐like) structure, in which the coordination environment of part of oxygen is transformed from 4Li‐O‐2TM octahedra to 3Li‐O‐3TM octahedra due to the partial substitution of TM for Li at Li‐2b site. Thus, some of the original unstable Li–O–Li configurations change to Li–O–TM configurations, forming strong TM–O covalent bonding and enhancing the structural stability of the oxygen. Consequently, the LR‐1.2 achieved a high reversible capacity of 282.3 mAh g−1 (Coulombic efficiency of 90.9%) at 0.1 C, exhibiting outstanding cycling stability (capacity retention of 90.3% after 400 cycles at 2 C) and superior rate performance. This work establishes a correlation between the microstructure modulation tuned by the Li/TM ratio and their electrochemical performance, offering insights into the design of cathode materials for high‐performance lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Density functional theory calculations have been performed to compare the HCHO decomposition on Co3O4(110)-A and (110)-B terminations. The results showed that the energy barriers of the two C–H bond cleavages of HCHO on the (110)-A termination were lower than those on the (110)-B termination, suggesting that the (110)-A termination had stronger HCHO decomposition ability than the (110)-B termination. Electronic structures revealed that the stronger HCHO decomposition ability of the (110)-A termination might be ascribed to the strong covalent bond between HCHO and the (110)-A termination, as well as the higher d-band center of Co3+ ions on the (110)-A termination. Furthermore, we proposed that the preparation of Co3O4 under oxygen-rich growth conditions was beneficial to HCHO decomposition because the (110)-A termination was more stable under oxygen-rich conditions. [ABSTRACT FROM AUTHOR]

Dynamic chemistry utilizing both covalent and noncovalent bonds provides valid protocols in manipulating properties of self‐assemblies and functions. Here we employ dynamic chemistry to realize multiple‐route control over supramolecular chirality up to five states. N‐protected fluorinated phenylalanine in the carboxylate state self‐assembled into achiral nanoparticles ascribed to the amphiphilicity. Protonation promoted one‐dimensional growth into helices with shrunk hydrophilicity, which in the presence of disulfide pyridine undergo chirality inversion promoted by the hydrogen bonding‐directed coassembly. Further interacting with the water‐soluble reductant cleavages the disulfide bond to initiate the rearrangement of coassemblies with a chirality inversion as well. Finally, by tuning the pH environments, aromatic nucleophilic substitution reaction between reduced products and perfluorinated phenylalanine occurs, giving distinct chiral nanoarchitectures with emerged luminescence and circularly polarized luminescence. We thus realized a particular five‐state control by combining dynamic chemistry at one chiral compound, which greatly enriches the toolbox in fabricating responsive chiroptical materials. [ABSTRACT FROM AUTHOR]

[2π + 2π]‐photocycloadditions and their ability to trigger controlled and reversible photoligation through disparate wavelengths provide an attractive platform to unlock advanced functionalities in soft materials. Yet, among the limited amount of functional motifs enabling reversible photoreactions, cyclability is often overlooked due to poor reaction yield and orthogonality. In this study, the advantageous photocharacteristics of the previously underexplored N‐methyl‐quinolinone photoresponsive motif are leveraged to create a covalent gated system, enabling controlled formation and cleavage of covalent bonds on demand. A systematic evaluation of individual cycloadditions and reversions on the molecular scale, including reaction rates, conversions, and photoproducts, allows identification of the required conditions for generating controlled photoreactions with a remarkable degree of cyclability; while, maintaining high reaction yields. Ultimately, these controlled and cyclable reactions are translated to a macromolecular scale, showcasing a comparable performance in initiating reversible photoligation, as observed at the molecular level. In addition, it is also shown that this progressive methodology can be leveraged to gain a comprehensive understanding of cyclability and clarify the factors contributing to its decreasing yield. Overall, unlocking the potential of quinolinone derivatives through this step‐by‐step approach lays the foundation for the development of highly controlled and responsive polymer materials with unprecedented potential. [ABSTRACT FROM AUTHOR]

Cross-linked polymers with covalent adaptable networks (CANs) can be reprocessed under external stimuli owing to the exchangeability of dynamic covalent bonds. Optimization of reprocessing conditions is critical since increasing the reprocessing temperature costs more energy and even deteriorates the materials, while reducing the reprocessing temperature via molecular design usually narrows the service temperature range. Exploiting CO2 gas as an external trigger for lowering the reprocessing barrier shows great promise in low sample contamination and environmental friendliness. Herein, we develop a type of CANs incorporated with ionic clusters that achieve CO2-facilitated recyclability without sacrificing performance. The presence of CO2 can facilitate the rearrangement of ionic clusters, thus promoting the exchange of dynamic bonds. The effective stress relaxation and network rearrangement enable the system with rapid recycling under CO2 while retaining excellent mechanical performance in working conditions. This work opens avenues to design recyclable polymer materials with tunable dynamics and responsive recyclability. Cross-linked polymers with covalent adaptable networks are reprocessed under external stimuli at high temperatures which might deteriorate their performance. Here, the authors introduce carbon dioxide responsive ionic clusters into covalent adaptable polymer networks to facilitate the exchange of dynamic bonds providing materials with a rapid recycling and good mechanical performance. [ABSTRACT FROM AUTHOR]

The crystal structures of zirconium diboride have been thoroughly explored up to 200 GPa by applying the particle‐swarm optimization technique in company with first‐principles calculations. The hexagonal ZrB2 with space group of P6/mmm is always stable in the pressure region of 0–200 GPa. Structurally, this structure consists of the intriguing regular ZrB12 hexagonal column and the planar hexagonal B ring unit. In addition, the stable AlB2–ZrB2 configuration is mechanically and dynamically stable as confirmed by the respective calculations of elastic constants and phonon dispersion curves. The hardness values exhibit a shrinking variation upon further compression, which mainly originates from the decreasing brittleness and degree of the directionality of the covalent bonds with the growing pressure. Interestingly, the analyses of the Poisson's ratio, density of states, electron location function and Bader charge substantiate that a combination of covalent and ionic characters exists in the AlB2–ZrB2 crystalline with the formidable covalent interaction in the BB bonds, and partially covalent and partially ionic interactions in the ZrB bonds. The hardness value for this phase unexpectedly reaches 45.41 GPa under ambient pressure, higher than the lower limit of superhard materials. [ABSTRACT FROM AUTHOR]

The construction of full‐color fluorescence systems has received widespread attention because of their applications in lighting materials, optoelectronic materials, and fluorescent probes. However, for the full‐color luminescence system based on trichromatic materials, there are no connections between materials of different luminescent colors. Herein, A new donor‐acceptor dye with red fluorescence was synthesized. The dye displays excellent optical properties of short half‐peak width and strong fluorescence emission. An effective energy transfer process from the dansyl donor to the acceptor was observed with a transfer efficiency of 81 %. Further, dyes with green and blue fluorescence were introduced to construct a full‐spectrum fluorescent system. Through exchange reactions of Diels‐Alder dynamic covalent bonds, red, green, and blue luminescence can be converted. This work provides a new idea for the design of full‐color fluorescent materials. [ABSTRACT FROM AUTHOR]

Thermosetting polymers crosslinked through covalent bonds are widely used in various fields due to their excellent mechanical properties and chemical stability. However, the non-recyclable nature of their fossil-based constituents hinders their post-service recycling and reshaping. This not only results in resource waste but also leads to environmental pollution, contradicting the principles of green and sustainable development. Dynamic covalent crosslinks are incorporated to turn conventional thermoset into covalent adaptable networks (CANs), enabling them to be processible and recyclable via bond exchange under specific stimuli. Normal covalent adaptable networks are highly flammable, which limits their applications and poses safety hazards. This review aims to provide insights to address this challenge. The state of the art of the molecular design of flame retarded CANs is summarized and classified through types of dynamic covalent bonds including classical ester exchange, imine exchange, disulfide exchange, Diels Alder reaction and transformation based on recently developed diselenide bonds, borate esters bonds, phenol carbamate bonds. Mechanical strength, dynamic behavior and flame retardancy of each type of CANs are described and compared quantitatively. Furthermore, the future prospects and challenges for development and application of these novel high-performance polymeric materials will be discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] Compared with layered materials such as graphite and transition metal disulfide compounds with highly anisotropic in-plane covalent bonds, it is inherently more challenging to obtain independent metallic two-dimensional films with atomic thickness. In this study, PtNi layered metallene nanobowls (LMBs) with multilayer atomic-scale nanosheets and bowl-like structures have been synthesized in one step using structural and electronic effects. The material has the advantage of catalyzing pH-universal hydrogen evolution reaction (HER). Compared with Pt/C, PtNi LMBs exhibited excellent HER activity and stability under all pH conditions. The overpotentials of 10 mA cm−2 at 0.5 M H 2 SO 4 , 1.0 M phosphate buffer and 1.0 M KOH were 14.8, 20.3, and 34.0 mV, respectively. Under acidic, neutral and alkaline conditions, the HER Faraday efficiencies reach 98.97%, 98.85%, and 99.04%, respectively. This study provides an example for the preparation of unique multilayer nanobowls, and also provides a basic research platform for the development of special HER materials. [ABSTRACT FROM AUTHOR]

Ferroptosis, a necrotic, iron‐dependent controlled cell death mechanism, is distinguished by the development of lipid peroxides to fatal proportions. Malignant tumours, influenced by iron to promote fast development, are vulnerable to ferroptosis. Based upon mounting evidence it has been observed that ferroptosis may be immunogenic and hence may complement immunotherapies. A new approach includes iron oxide‐loaded nano‐vaccines (IONVs), having supremacy for the traits of the tumour microenvironment (TME) to deliver specific antigens through improving the immunostimulatory capacity by molecular disintegration and reversible covalent bonds that target the tumour cells and induce ferroptosis. Apart from IONVs, another newer approach to induce ferroptosis in tumour cells is through oncolytic virus (OVs). One such oncolytic virus is the Newcastle Disease Virus (NDV), which can only multiply in cancer cells through the p53‐SLC7A11‐GPX4 pathway that leads to elevated levels of lipid peroxide and intracellular reactive oxygen species leading to the induction of ferroptosis that induce ferritinophagy. [ABSTRACT FROM AUTHOR]

The three typical coals selected in this study (Shuangyi coal (SY), Hengsheng coal (HS) and Ningxia anthracite (NX)) are widely used in western China, but their pyrolysis characteristics have been less studied. In this study, based on the simultaneous thermal analysis-Fourier transform infrared spectroscopy (STA-FTIR) technique, the effects of different coal types, particle sizes and heating rates on the pyrolysis characteristics of coal powder were investigated. The results showed that the weight loss behaviors of different types of coals with different particle sizes varied, as influenced by the type of coal and heat transfer. When the particle size increased from 170 μm to 380 μm, the weight loss rate decreased by 2.95% and 24.45% for SY and NX coals while increased by 4.81% for HS coals; whereas for the maximum decomposition rate, both SY and HS coals showed an increasing tendency (increased by 2.76% and 9.32%), while NX coals decreased by 21.43%. The R2 of the three coal DTG curves fitted by subcurves was all 0.999, which proved that the nature of coal weight loss was the coupling effect of certain types of chemical reactions or covalent bond breakage. Real-time infrared spectroscopy was combined with covalent bonding to explore the major gas products and their influence by particle size. The activation energies at different temperatures were calculated by the Coats-Redfern method, in which the activation energies of the fast pyrolysis stage of HS coal were 1.68 and 2.75 times higher than those of the other two stages, 1.79 and 3.03 times higher than those of SY coal, and 1.99 and 1.11 times higher than those of NX coal, respectively. [ABSTRACT FROM AUTHOR]

Organic molecules with dynamic covalent-bonding characteristics have attracted much attention for their important role in constructing stimulus-responsive smart materials. However, it is difficult to realize sensitive and reversible covalent bond cleavage/formation through external stimuli in the aggregated state of molecules. Herein, a series of 2,3-diphenylmaleonitriles (DPMNs) with photoinduced π-bond cleavage properties have been designed and synthesized to construct the dynamic covalent bond materials. The cis-form 2,3-diphenylmaleonitriles (Z-DPMNs) exhibit significant photochromism in both solid and solution states under ultraviolet light and visible light. The photochromism stems from the photoinduced π-bond splitting of Z-DPMNs, resulting in a transition from the closed-shell to open-shell structure. Moreover, the twisted structure and molecular stacking of Z-DPMNs, the push-pull electron effect of substituents, and the external factors including temperature and solvent polarity have important effects on the dynamic conversion of π-bonds. Based on the sensitive and reversible optical performance transformation, Z-DPMNs can be applied as safety ink in anti-counterfeiting, information encryption and storage systems. This work not only provides an approach for constructing dynamic covalent bonds but also greatly enriches stimulus-responsive materials. Dynamic covalent bonding can be useful in preparation of stimuli responsive materials, but this is challenging in the aggregated state. Here, the authors report the development of compounds with photoinduced π-bond cleavage to prepare dynamic covalent bond materials. [ABSTRACT FROM AUTHOR]

Herein, we investigated hydrogels composed of boronic-acid-functionalized alginate and blended with polyvinyl alcohol (PVA) of different molecular weights to control the release of metoclopramide hydrochloride as a function of pH and shear stress. The functionalization of alginate introduced dynamic covalent bonding and pH-responsive properties that can modulate network connectivity. The study investigated the viscoelastic properties of the hydrogels, their drug release profiles, and their responsiveness to changes in pH and shear forces. The results showed that a higher PVA molecular weight and alkaline pH conditions increased hydrogel viscosity and stiffness due to a more stable and interconnected network structure than acidic pH. Metoclopramide release revealed that the hydrogels exhibited pH-responsive drug release behavior. The drug was more readily released under acidic conditions due to the instability of sp2-hybridized boronate ester bonds. The influence of shear forces on the release of metoclopramide was also investigated at shear rates of 1, 10, and 100 s−1, revealing their effect on matrix stiffening. Research shows that AlgBA/PVA hydrogels have unique properties, such as dynamic covalent bonding, that make them sensitive to external mechanical forces. This sensitivity makes them ideal for applications where physiological conditions trigger drug release. [ABSTRACT FROM AUTHOR]

Rotaxanes are typically prepared using covalent bonds to trap a wheel component onto an axle molecule, and rotaxane-type wheel–axle assembly using only noncovalent interactions has been far less explored. Here we show that a dinickel(II) metallomacrocycle forms two different types of wheel–axle assemblies with a dibenzylammonium axle molecule based only on noncovalent interactions. The non-threaded assembly was obtained by introduction of Ni2+ into the macrocycle before the complexation with the axle molecule (metal-first method). The non-threaded assembly was in rapid equilibrium with each of the components in solution. The threaded assembly was obtained by introduction of Ni2+ after the formation of a pseudorotaxane from the non-metalated wheel and the axle molecule (axle-first method). The threaded assembly was not in equilibrium with the dissociated species even though it was maintained only by noncovalent interactions. Thus, formation of one of the non-threaded and threaded wheel–axle assemblies over the other is governed by the assembly pathway. Mechanically interlocked rotaxanes are typically prepared using covalent bonds to trap a wheel component onto an axle molecule, and rotaxane-type wheel–axle assembly using only noncovalent interactions has been far less explored. Here, a dinickel(II) metallomacrocycle is found to form two different types of wheel–axle assemblies, with a dibenzylammonium axle molecule forming both non-threaded and rotaxane-type threaded assemblies, based only on noncovalent interactions, with formation of one over the other governed by the assembly pathway. [ABSTRACT FROM AUTHOR]