Reverse Transformation Research Articles

Visible light‐responsive azo‐based smart materials: Design, performance, and applications in energy storage

AbstractAzobenzene and its derivatives are the most extensively investigated and applied molecular photoswitches, which can undergo reversible transformation between trans and cis isomers upon irradiation with light at specific wavelengths. Through structural geometry transformation, the property alterations can be integrated into smart materials to meet diverse application requirements. Most azo‐based photoswitches require UV light for activation. However, complete activation within the visible or even near‐infrared light range could offer several benefits for photoswitch applications, including improved biocompatibility, better light penetration, and enhanced solar light utilization efficiency. This review presents an overview of the development of visible‐light responsive azo‐based materials, covering molecular design strategies and their applications in energy storage. Recent efforts aimed at enhancing the performance of azo‐based energy storage materials are highlighted. According to the different strategies for improving energy storage properties, these materials are categorized as those that directly increase isomerization energy and those that introduce phase transition energy. Furthermore, we discuss the challenges and opportunities in this field with a view to inspire further exploration.

Interfacial synergy in twinborn CoS2/CoS1.097 heterojunction to promote sulfur conversion kinetics in lithium-sulfur batteries

The rational design of sulfur hosts is essential for mitigating the shuttle effect of lithium polysulfides (LiPSs) and improving the sluggish conversion kinetics of sulfur during multi-step phase transition. Herein, a twinborn CoS2/CoS1.097 heterojunction encapsulated in N-doped hollow carbon polyhedrons and in-situ generated CNTs (CoS2/CoS1.097@NC/CNT) was elaborately synthesized and utilized as the electrocatalyst in sulfur cathodes. The CoS2/CoS1.097 heterojunction provides abundant chemisorption sites that facilitate the formation of chemical bonds with polysulfides, thereby effectively adsorbing LiPSs. More importantly, the spontaneously generated internal electric field at the CoS2/CoS1.097 interface accelerates electron transfer, which promotes the reversible transformation between LiPSs and Li2S. Additionally, the hollow carbon polyhedrons and grafted CNTs not only effectively confine sulfur, but also provide extra buffer space for the sulfur evolution reaction. Benefiting from these characteristics, the battery assembled with CoS2/CoS1.097@NC/CNT/S cathode exhibits a remarkable initial capacity of 1454.4mAh/g at 0.1C), excellent rate capability of 674.7mAh/g at 4C, and outstanding capacity retention of 604.7mAh/g over 500 cycles at 2C (∼73.1 % of initial capacity).

The Reversible Electron Transfer Within Stimuli-Responsive Hydrochromic Supramolecular Material Containing Pyridinium Oxime and Hexacyanoferrate (II) Ions

The structural and electronic features of the stimuli-responsive supramolecular inter-ionic charge-transfer material containing electron accepting N-benzylyridinium-4-oxime cation (BPA4+) and electron donating hexacyanoferrate (II) are reported. The study of reversible stimuli-induced transformation between hydrated reddish-brown (BPA4)4[Fe(CN)6]·10H2O and anhydrous blue (BPA4)4[Fe(CN)6] revealed the origin of observed hydrochromic behavior. The comparison of the crystal structures of decahydrate and anhydrous phase showed that subsequent exclusion/inclusion of lattice water molecules induces structural relocation of one BPA4+ that alter the donor-to-acceptor charge-transfer states, resulting in chromotropism seen as reversible reddish-brown to blue color changes. The decreased donor-acceptor distance in (BPA4)4[Fe(CN)6] enhanced charge-transfer interaction allowing charge separation via one-electron transfer, as evidenced by in-situ ESR and FTIR spectroscopies. The reversibility of hydrochromic behavior was demonstrated by in-situ HT-XRPD, hot-stage microscopic and in situ diffuse-reflectance spectroscopic analyses. The insight into electronic structural features was obtained with density functional theory calculations, employed to elucidate electronic structure for both compounds. The electrical properties of the phases during dehydration process were investigated by temperature-dependent impedance spectroscopy.

Spinel oxide enables high-temperature self-lubrication in superalloys

The ability to lubricate and resist wear at temperatures above 600 °C in an oxidative environment remains a significant challenge for metals due to their high-temperature softening, oxidation, and rapid degradation of traditional solid lubricants. Herein, we demonstrate that high-temperature lubricity can be achieved with coefficients of friction (COF) as low as 0.10-0.32 at 600-900 °C by tailoring surface oxidation in additively-manufactured Inconel superalloy. By integrating high-temperature tribological testing, advanced materials characterization, and computations, we show that the formation of spinel-based oxide layers on superalloy promotes sustained self-lubrication due to their lower shear strength and more negative formation and cohesive energy compared to other surface oxides. A reversible phase transformation between the cubic and tetragonal/monoclinic spinel was driven by stress and temperature during high temperature wear. To span Ni- and Cr-based ternary oxide compositional spaces for which little high-temperature COF data exist, we develop a computational design method to predict the lubricity of oxides, incorporating thermodynamics and density functional theory computations. Our finding demonstrates that spinel oxide can exhibit low COF values at temperatures much higher than conventional solid lubricants with 2D layered or Magnéli structures, suggesting a promising design strategy for self-lubricating high-temperature alloys.

Optimizing Reversible Phase‐Transformation of FeS2 Anode via Atomic‐Interface Engineering Toward Fast‐Charging Sodium Storage: Theoretical Predication and Experimental Validation

AbstractSodium‐storage performance of pyrite FeS2 is greatly improved by constructing various FeS2‐based nanostructures to optimize its ion‐transport kinetics and structural stability. However, less attention has been paid to rapid capacity degradation and electrode failure caused by the irreversible phase‐transition of intermediate NaxFeS2 to FeS2 and polysulfides dissolution upon cycling. Under the guidance of theoretical calculations, coupling FeS2 nanoparticles with honeycomb‐like nitrogen‐doped carbon (NC) nanosheet supported single‐atom manganese (SAs Mn) catalyst (FeS2/SAs Mn@NC) via atomic‐interface engineering is proposed to address above challenge. Systematic electrochemical analyses and theoretical results unveil that the functional integration of such two type components can significantly enhance ionic conductivity, accelerate charge transfer efficiency, and improve Na+‐adsorption capability. Particularly, SAs Mn@NC with Mn‐Nx coordination center can reduce the decomposition barrier of Na2S and NaxFeS2 to further accelerate reversible phase transformation of Fe/Na2S→NaFeS2→FeS2 and polysulfides decomposition. As predicted, such FeS2/SAs Mn@NC showcases outstanding rate capability and fascinating cyclic durability. A sequence of kinetic studies and ex situ characterizations provide the comprehensive understanding for ion‐transport kinetics and phase‐transformation process. Its practical use is further demonstrated in sodium‐ion full cell and capacitor with impressive electrochemical capability and excellent energy‐density output.

Enhancement of Selective Catalytic Oxidation of Lignin β-O-4 Bond via Orbital Modulation and Surface Lattice Reconstruction.

The orbital modulation and surface lattice reconstruction represent an effective strategy to regulate the interaction between catalyst interface sites and intermediates, thereby enhancing catalytic activity and selectivity. In this study, the crystal surface of Au-K/CeO2 catalyst can undergo reversible transformation by tuning the coordination environment of Ce, which enables the activation of the Cβ-H bond and the oxidative cleavage of the Cβ-O and Cα-Cβ bonds, leading to the cleavage of 2-phenoxy-1-phenylethanol. The t2g orbitals of Au 5d hybridize with the 2p orbitals of lattice oxygen in CeO2 via π-coordination, modulating the coordination environment of Ce 4 f and reconstructing the lattice oxygen in the CeO2 framework, as well as increasing the oxygen vacancies. The interface sites formed by the synergy between Au clusters in the reconstructed Ce-OL1-Au structure and doped K play dual roles. On the one hand, it activates the Cβ-H bond, facilitating the enolization of the pre-oxidized 2-phenoxy-1-phenylethanone. On the other hand, through single-electron transfer involving Ce3+ 4f1 and the adsorption by oxygen vacancies, it enhances the oxidative cleavage of the Cβ-O and Cα-Cβ bonds. This study elucidates the complex mechanistic roles of the structure and properties of Au-K/CeO2 catalyst in the selective catalytic oxidation of lignin β-O-4 bond.

Effect of Deformed Prior Austenite Characteristics on Reverse Phase Transformation and Deformation Behavior of High-Strength Medium-Mn Steel.

In this study, microstructure evolution during prior austenite decomposition and reverse phase transformation processes was revealed in a high-strength medium-Mn steel. Furthermore, the relationship between deformed prior austenite characteristics and deformation behavior was studied. The results indicated that the recovery and recrystallization of the deformed prior austenite were significantly inhibited during hot rolling in the non-recrystallized zone, the grain size was obviously refined along the normal direction (ND), and that the strain hardening of prior austenite via hot deformation could increase the resistance of shear transformation, resulting in the preservation of high-density lattice defects in the quenched martensite matrix. Before the nucleation of intercritical austenite, the dislocation and grain boundary can provide fast diffusion paths for C and Mn, and the enrichment of C and Mn before intercritical austenite formation can reduce the critical temperature of ferrite/austenite transformation. The nucleated sites and driving force for intercritical austenite were strongly increased by rolling in the non-recrystallization region. The resistance of crack propagation was found to be enhanced by the sustained transformation-induced plasticity (TRIP) effect (via retained austenite with different stability) and for the laminated microstructure, the optimum properties were obtained as being a combination of yield strength of 748 MPa, tensile strength of 952 MPa, and total elongation of 26.2%.

A highly visible-transparent thermochromic smart window with broadband infrared modulation for all-season energy savings

Abstract Thermochromic smart windows effectively reduce the energy consumption for building through passive light modulation including the transmission of visible (TVis), near-infrared (TNIR), and the emissivity of mid-infrared (εMIR) in response to the ambient temperature change. However, thermochromic windows that maintain high TVis while modulating TNIR and εMIR simultaneously are highly desirable but still challenging. Here, we develop a thermochromic smart window based on a two-way shape memory polymer to enable reversible transformation and achieve TNIR modulation of 44.0% and εMIR modulation of 76.5% while maintaining high TVis (>50%). Compared to traditional windows based on silica glass, this device shows 4°C lower temperature in summer daytime, 2°C higher in winter daytime, and 1°C higher in spring nighttime. It is expected that our device can achieve greater annual energy savings in comparison with commercial glass anywhere in the world and promote the progress of thermochromic windows for energy-efficient buildings.

Geothermo-mechanical energy conversion using shape memory alloy heat engine

The shift towards renewable energy sources like geothermal energy has become desirable due to the recurrent energy crisis and global warming challenges influenced by fossil fuels. Geothermo-mechanical energy conversion using shape memory alloy (SMA) heat engines presents a novel and sustainable approach for harnessing geothermal energy. Shape memory alloys, known for their ability to undergo reversible phase transformations driven by temperature changes, are ideal for thermal-to-mechanical energy conversion. This paper explores the design and performance of an SMA heat engine that utilizes geothermal heat sources to drive mechanical work. The engine operates by cycling between the high-temperature geothermal environment and a cooler sink, exploiting the shape memory effect to generate mechanical motion. By integrating geothermal energy and SMA technology, this system offers a potential solution for renewable energy generation, with applications in remote or off-grid locations. The paper also investigates output power and the thermodynamic efficiency. A model is formulated and the engine behavior is simulated. A series of experiments are conducted for engine output power and efficiency. The model is compared to the experimental data for validation. The engine developed a maximum power of 3.5, 8.5, and 11.5 watts at 60, 80, and 90 °C respectively. The proposed SMA-based geothermo-mechanical energy conversion system offers a promising solution for efficient, reliable, and scalable geothermal energy harvesting. This research contributes to the development of innovative, efficient geothermal energy conversion technologies, supporting global renewable energy goals and reducing greenhouse gas emissions. This innovative energy conversion mechanism could play a key role in the future of sustainable power generation.

Anti-interference flexible temperature-sensitive/strain-sensing aerogel fiber for cooperative monitoring of human body temperature and movement information

In recent years, multi-functional flexible sensing fibers capable of detecting various physical and chemical stimuli capabilities have made significant advancements. However, the cross-sensitivity of the sensing materials to other stimuli can considerably reduce their sensitivity and accuracy of these multifunctional fibers. In this study, we initially fabricated a blending type (BAF) and a core-sheath type (CAF) strain-sensing aerogel fiber using an optimized one-step wet spinning process. Then, we coated the aerogel fiber with cholesteric liquid crystal as the middle layer and waterborne polyurethane as the outer layer to obtain a temperature-sensitive/strain-sensing aerogel fiber (TSAF). TSAF demonstrates distinct multi-model strain sensing performance, enabling the detection of tensile strains (0.1–111.5 %), bending strains (40°–160°), and compression strains. Moreover, within the ultra-narrow temperature range of 34 °C–38 °C, TSAF undergoes reversible color transformations from yellow-green-blue-purple, against both bright and dark backgrounds. This unique feature offered high sensitivity, rapid response time, and diverse color variations. By integrating fibers into clothing, a collaborative sensing system can be established to simultaneously monitor human physiology and movement information. These advancements hold significant potential for applications in smart clothing, medical care, and other fields.

Effect of cyclic loading on microstructure and plastic deformation in heat-treated Co–28Cr–6Mo alloy fabricated via laser powder bed fusion: An in situ synchrotron X-ray diffraction study

We present a systematic microstructure-oriented plasticity investigation of an additively manufactured cobalt-based alloy aiming to relate microstructural changes to the fatigue resistance. A load-controlled cyclic test in the low-cycle fatigue regime was utilized to study mechanical response and microstructural changes in the alloy after reverse phase transformation heat treatment. Deformation-induced FCC → HCP phase transformation was followed using in situ synchrotron X-ray diffraction combined with ex situ electron backscatter diffraction and scanning electron microscopy. Scanning transmission electron microscopy provided experimental evidence of the presence of precipitates in the solution annealed sample. It was found, that a stepwise increase in plastic deformation is attributed to nucleation and growth of different martensitic crystallographic variants. These insights into plasticity and microstructural changes suggest that the reverse phase transformation heat treatment is an effective approach for improving the fatigue resistance of low stacking fault energy alloys, that are susceptible to deformation-induced martensitic transformation.

Deformation mechanism of a metastable medium entropy alloy strengthened by the synergy of heterostructure design and cryo-pre-straining

Face-centered cubic (FCC) medium entropy alloys (MEAs) have received considerable attention due to their impressive mechanical properties and responses. However, their practical application is limited by their modest yield strengths. The potential enhancement of the mechanical properties of single-phase MEAs was explored in this study through a synergistic approach combining heterogeneous structure design with subsequent cryo-pre-straining. A heterogeneous lamella structure was produced in a single-phase Fe55Mn20Cr15Ni10 MEA via two-step rolling and annealing. Cryo-pre-straining at varying degrees (6, 12, 21, and 36%) introduced hexagonal close-packed (HCP) phase, high-density dislocations, twins, and stacking faults, leveraging the reduced stacking fault energy at cryogenic temperatures. This process enhanced the alloy's yield strength from 353 MPa to 1.2 GPa (compared to the baseline uniform coarse-grained structure), while maintaining an acceptable total elongation of 8.4%. The impact of cryo-pre-straining on the microstructure and mechanical properties of the MEA was assessed using in-situ synchrotron X-ray diffraction analysis. Cryo-pre-straining (36%) achieved a higher dislocation density (6.1 × 1015m−2) compared to room-temperature straining (2.5 × 1015m−2). The stress contribution from HCP-martensite and the evolution of dislocation density during loading were quantified, along with observations of negative stacking fault probability and strain-induced HCP→FCC reverse transformation in cryo-pre-strained samples under loading conditions. Furthermore, the contributions of regulated microstructures to the enhancement of yield strength were quantitatively assessed.

Electrochemically Switchable Sulfurized Polyacrylonitrile for Controllable Recovery of Copper in Wastewater Based on Reversible Adsorption/Desorption Regulation.

Within the context of circular economy and industrial ecology, adsorption offers an effective manner for recycling resources from wastewater, but controllable desorption remains a challenge. Inspired by metal-thiol binding and reversible thiol-disulfide redox transformation in biological systems, this study reports the development of a reversible adsorption/desorption (RAD) system for controllable recovery of copper based on electrochemically switchable sulfurized polyacrylonitrile (SPAN). Density functional theory calculations offered theoretical prediction for the formation of S-Cu bonds and reversible weak interaction between S-S bonds and Cu2+. The SPAN anchored onto titanium suboxide ceramic foam (SPAN@TiSO) could regulate Cu2+ adsorption/desorption stimulated by the electrode potential, indicated by the adsorption capacity of 243.3 mg g-1 (30 min) at 0.2 V vs SHE and a desorption efficiency of 98.4% (5 min) at 0.8 V vs SHE. Electrochemical analysis revealed that the reversible redox transformation of S-S/-S- groups in SPAN was responsible for selective adsorption and rapid desorption in response to the electrode potential. This study provides a proof-of-concept demonstration of an electrochemically switchable polymer to build up a reversible RAD system for controllable recovery of heavy metals in wastewater, making value-added resource recovery more efficient, more intelligent, and more sustainable.

Influence of heating rate on the evolution of post-annealed microstructure in Nb–Ti microalloyed steel: Interplay with initial cold-rolled microstructure

This study focuses on understanding the complex interactions between the initial cold-rolled microstructure and the heating rate, and how these factors influence the post-annealed microstructure, particularly the fraction of polygonal ferrite, in the Nb–Ti microalloyed steel. Key findings include that increasing the heating rate from 3 °C/s to 30 °C/s enhances the kinetics of reverse transformation to austenite, resulting in a larger fraction of new ferrite and thus a higher proportion of polygonal ferrite in the post-annealed microstructure in most cases. Interestingly, in scenarios where recrystallization can occur by altering the initial microstructure, the combined evolution of recrystallized and new ferrite enlarges the fraction of polygonal ferrite at slower heating rates of 3 °C/s. It indicates that the contribution of recrystallization and reverse transformation on the evolution of polygonal ferrite depends on the interplay between initial microstructure and the heating rate. Further, the calculations of the austenite/ferrite interface velocity suggest that the accelerated reverse transformation to austenite, facilitated by increased heating rates, is little affected by kinetic transitions.

Black Body Cavity Apparatus for Measuring the Emissivity of Nickel-Titanium-Based Shape-Memory Alloys and Other Metals

Nickel-titanium (NiTi)-based shape-memory alloys (SMAs) have various applications in biomedicine, actuators, aerospace technologies, and elastocaloric devices, due to their shape-memory and super-elastic effects. These effects are induced in SMAs by a reversible martensitic phase transformation. This transformation can be achieved by applying stress or temperature differences. It is extremely difficult to measure the temperature of NiTi elements with contact thermometers because they disturb the phase transformation phenomenon. An alternative approach is contactless infrared thermography for which accurate emissivity data are mandatory. To determine the temperature distribution in NiTi components with an infrared camera, a newly constructed apparatus is presented to measure the emissivity of metals. For this purpose, a state-of-the-art infrared camera was employed to analyze the emissivity behavior with temperature, especially during the phase transformation. The emissivity of the NiTi samples was systematically studied by comparing them with a reference-quality black body cavity (BBC) having an emissivity better than 0.995. Calibration measurements revealed that the maximum deviation of the BBC temperature measured with the infrared camera was only 0.15% (0.45 K) from its temperature measured with the built-in contact thermometers. The apparatus was validated by measuring the emissivity of a polished aluminum sample and found to be in good agreement with literature data, particularly for temperatures above 340 K. Finally, the emissivity of two rough and one polished NiTi samples was measured covering the temperature range from 313 K to 423 K with an expanded uncertainty of about 0.02 (k=2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$k=2$$\\end{document}). The studied NiTi samples have an atomic percent composition of Ni42.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {Ni}_{42.5}$$\\end{document}Ti49.9\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {Ti}_{49.9}$$\\end{document}Cu7.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {Cu}_{7.5}$$\\end{document}Cr0.1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {Cr}_{0.1}$$\\end{document}. We observed that the emissivity of NiTi varies between 0.17 and 0.31 depending on temperature. As the temperature rises, the emissivity increases rapidly during the phase transformation, and it decreases gradually beyond the austenite finish temperature. In addition, the emissivity of NiTi depends on the microstructure of the martensite and austenite phases and the surface roughness of the samples.

Phase reversion mediated the dual heterogeneity of grain size and dislocation density in an equiatomic CrCoNi medium-entropy alloy

An ultra-high strain rate (104 s-1) dynamic plastic deformation treatment at liquid nitrogen temperature (LNT-DPD) followed by annealing is carried out to obtain dual heterogeneity of grain size and dislocation density in an equiatomic CrCoNi medium entropy alloy (MEA). Such extreme loading conditions resulted in extensive phase transformation in this MEA. Subsequent annealing at 650°C for 1 h further induced reverse phase transformation and partial recrystallization, forming a complex heterogeneous microstructure characterized by nested trimodal grain sizes and partitioned dislocation density. A superior yield strength of ∼800MPa and a good ductility of ∼40% were simultaneously achieved in this heterogeneous alloy. In order to reveal the effects of grain size and dislocation density distributions on the mechanical property improvements, the underlying deformation mechanisms were systematically discussed. High density of geometrically necessary dislocations (GNDs) would be induced in complex heterogeneous structures during tensile deformation due to strain gradients or partitioning between different regions, which would lead to additional strengthening and work hardening. These results provide a novel approach to overcome the strength-ductility trade-off dilemma for FCC-structured MEAs.

Magnetic‐induced isomerization of paramagnetic bridged azobenzene derivatives with conjugated alkyl chains

AbstractInducing a reversible structural transformation in organic photochromophores under the effect of a magnetic field is challenging owing to their poor magnetic properties. Compared with common azobenzene materials, bridged azobenzene materials exhibit a considerable potential for rapid trans‐cis isomerization induced by an external magnetic field because of the restricted torsion of N=N bonds during the transformation. Herein, we designed and synthesized pentenyl‐grafted bridged azobenzene (BA‐X5), hexenyl‐grafted bridged azobenzene (BA‐X6), and pentynyl‐grafted bridged azobenzene (BA‐Q5). Density functional theory calculations indicate that the activation energy for the trans‐cis transition of BA‐X5 and BA‐X6 is ~18.0 kcal/mol, which is 8.2% lower than that of BA‐Q5 (19.6 kcal/mol). The results obtained using EPR and a superconducting quantum interference device demonstrate that during the isomerization process, a net spin reduction of bridged azobenzene occurred because of the aggregation of the electron cloud toward the C−N bond, leading to a reduction in the paramagnetism of the materials. BA‐X5 and BA‐X6 exhibit a clear and rapid magnetically induced trans‐cis isomerization with short half‐lives, which are 10.4% and 16.9%, respectively, lower than those obtained under dark conditions. In contrast, the isomerization of BA‐Q5 under the effect of the same magnetic field does not change. Magnetically induced isomerization might be attributed to the combined effect of the magnetothermal effect, changes in the net spin density of the electron cloud, and regularity of molecular arrangement under the effect of the magnetic field. These results provide a basis for exploring the design and research of magnetically controlled azobenzene derivatives.

Stereoselective Synthesis of Oxetanes Catalyzed by an Engineered Halohydrin Dehalogenase.

Although biocatalysis has garnered widespread attention in both industrial and academic realms, the enzymatic synthesis of chiral oxetanes remains an underdeveloped field. Halohydrin dehalogenases (HHDHs) are industrially relevant enzymes that have been engineered to accomplish the reversible transformation of epoxides. In this study, a biocatalytic platform was constructed for the stereoselective kinetic resolution of chiral oxetanes and formation of 1,3-disubstituted alcohols. HheC from Agrobacterium radiobacter AD1 was engineered to identify key variants capable of catalyzing the dehalogenation of γ-haloalcohols (via HheC M1-M3) and ring opening of oxetanes (via HheC M4-M5) to access both (R)- and (S)-configured products with high stereoselectivity and remarkable catalytic activity, yielding up to 49 % with enantioselectivities exceeding 99 % ee and E>200. The current strategy is broadly applicable as demonstrated by expansion of the substrate scope to include up to 18 examples for dehalogenation and 16 examples for ring opening. Additionally, the functionalized products are versatile building blocks for pharmaceutical applications. To shed light on the molecular recognition mechanisms for the relevant variants, molecular dynamic (MD) simulations were performed. The current strategy expands the scope of HHDH-catalyzed chiral oxetane ring construction, offering efficient access to both enantiomers of chiral oxetanes and 1,3-disubstituted alcohols.

Stereoselective Synthesis of Oxetanes Catalyzed by an Engineered Halohydrin Dehalogenase

AbstractAlthough biocatalysis has garnered widespread attention in both industrial and academic realms, the enzymatic synthesis of chiral oxetanes remains an underdeveloped field. Halohydrin dehalogenases (HHDHs) are industrially relevant enzymes that have been engineered to accomplish the reversible transformation of epoxides. In this study, a biocatalytic platform was constructed for the stereoselective kinetic resolution of chiral oxetanes and formation of 1,3‐disubstituted alcohols. HheC from Agrobacterium radiobacter AD1 was engineered to identify key variants capable of catalyzing the dehalogenation of γ‐haloalcohols (via HheC M1‐M3) and ring opening of oxetanes (via HheC M4‐M5) to access both (R)‐ and (S)‐configured products with high stereoselectivity and remarkable catalytic activity, yielding up to 49 % with enantioselectivities exceeding 99 % ee and E>200. The current strategy is broadly applicable as demonstrated by expansion of the substrate scope to include up to 18 examples for dehalogenation and 16 examples for ring opening. Additionally, the functionalized products are versatile building blocks for pharmaceutical applications. To shed light on the molecular recognition mechanisms for the relevant variants, molecular dynamic (MD) simulations were performed. The current strategy expands the scope of HHDH‐catalyzed chiral oxetane ring construction, offering efficient access to both enantiomers of chiral oxetanes and 1,3‐disubstituted alcohols.

Highly efficient electrosynthesis of hydrogen peroxide through reversible transformation between catechol and o-benzoquinone on polydopamine modified carbon black

Carbon-based materials are more promising catalysts for H2O2 electrochemical production. However, the common method for modifying carbon-based materials is surface functionalization with harsh and uncontrollable reaction conditions, hindering the precise regulation of the active sites. Herein, we proposed a carbon-based material modified by polydopamine (CB-PDA) that was easily prepared and used in air diffusion electrode system for H2O2 production. The rapid and reversible transformation between catechol and o-benzoquinone on PDA could improve the H2O2 selectivity from 75.5 % to 97.0 % during the electrocatalytic process. The detection of adsorbed *HOOH and *OOH in oxygen reduction reaction proved the preference of CB-PDA for the two-electron pathway. The H2O2 formation rate constant of CB-PDA increased significantly from 25.85 to 60.82 mM h−1. The highest cumulative H2O2 concentration could reach 10200 mg L−1 in 9 h. Long-term operation tests proved the good operational stability. Furthermore, this system was cost-effective without additional aeration energy consumption and could achieve rapid disinfection in 10 min, which would have great potential to be used in environmental remediation.