Rational Design Research Articles

Machine Learning-Enhanced Quantum Chemistry-Assisted Refinement of the Active Site Structure of Metalloproteins.

Understanding the fine structural details of inhibitor binding at the active site of metalloenzymes can have a profound impact on the rational drug design targeted to this broad class of biomolecules. Structural techniques such as NMR, cryo-EM, and X-ray crystallography can provide bond lengths and angles, but the uncertainties in these measurements can be as large as the range of values that have been observed for these quantities in all the published structures. This uncertainty is far too large to allow for reliable calculations at the quantum chemical (QC) levels for developing precise structure-activity relationships or for improving the energetic considerations in protein-inhibitor studies. Therefore, the need arises to rely upon computational methods to refine the active site structures well beyond the resolution obtained with routine application of structural methods. In a recent paper, we have shown that it is possible to refine the active site of cobalt(II)-substituted MMP12, a metalloprotein that is a relevant drug target, by matching to the experimental pseudocontact shifts (PCS) those calculated using multireference ab initio QC methods. The computational cost of this methodology becomes a significant bottleneck when the starting structure is not sufficiently close to the final one, which is often the case with biomolecular structures. To tackle this problem, we have developed an approach based on a neural network (NN) and a support vector regression (SVR) and applied it to the refinement of the active site structure of oxalate-inhibited human carbonic anhydrase 2 (hCAII), another prototypical metalloprotein target. The refined structure gives a remarkably good agreement between the QC-calculated and the experimental PCS. This study not only contributes to the knowledge of CAII but also demonstrates the utility of combining machine learning (ML) algorithms with QC calculations, offering a promising avenue for investigating other drug targets and complex biological systems in general.

Structure and Chemical Reactivity of Y-Stabilized ZrO2 Surfaces: Importance for the Water-Gas Shift Reaction.

The surface structure and chemical properties of Y-stabilized zirconia (YSZ) have been subjects of intense debate over the past three decades. However, a thorough understanding of chemical processes occurring at YSZ powders faces significant challenges due to the absence of reliable reference data acquired for well-controlled model systems. Here, we present results from polarization-resolved infrared reflection absorption spectroscopy (IRRAS) obtained for differently oriented, Y-doped ZrO2 single-crystal surfaces after exposure to CO and D2O. The IRRAS data reveal that the polar YSZ(100) surface undergoes reconstruction, characterized by an unusual, red-shifted CO band at 2132 cm-1. Density functional theory calculations allowed to relate this unexpected observation to under-coordinated Zr4+ cations in the vicinity of doping-induced O vacancies. This reconstruction leads to a strongly increased chemical reactivity and water spontaneously dissociates on YSZ(100). The latter, which is an important requirement for catalysing the water-gas-shift (WGS) reaction, is absent for YSZ(111), where only associative adsorption was observed. Together with a novel analysis Scheme these reference data allowed for an operando characterisation of YSZ powders using DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy). These findings facilitate rational design and tuning of YSZ-based powder materials for catalytic applications, in particular CO oxidation and the WGS reaction.

Modulating the Microstructure and Surface Acidity of MnO2 by Doping-Induced Phase Transition for Simultaneous Removal of Toluene and NOx at Low Temperature.

It is a great challenge to remove VOCs and NOx simultaneously from flue gas in nonelectric industries. This study focuses on the construction of Fe-MnO2 catalysts that perform well in the simultaneous removal of toluene and NOx at low temperatures. Utilizing the Fe-induced phase transition of MnO2, Fe-MnO2-F&R catalysts with a composite morphology of nanoflowers and nanorods were successfully prepared that provided an abundant microporous structure to facilitate the diffusion of molecules of different sizes. Through in-depth investigation of the active sites and reaction mechanism, we discovered that Fe-induced phase transition could modulate the surface acidity of Fe-MnO2-F&R. The higher concentration of surface Mn4+ provided numerous Brønsted acid sites, which effectively promoted the activation of toluene to reactive intermediates, such as benzyl alcohol/benzoate/maleic acid. Simultaneously, Fe provided a large number of Lewis acid sites that anchor and activate NH3 species, thereby inhibiting NH3 nonselective oxidation. Furthermore, additional Brønsted acid sites were generated during the simultaneous reaction process, enhancing toluene activation. Consequently, the simultaneous removal of toluene and NOx was achieved through regulation of the physical structure and the concentration of acidic sites. The present work provides new insights into the rational design of bifunctional catalysts for the synergistic control of VOCs and NOx emissions.

Inhibition of Phase Transition in Amorphous Niobium Oxide by Covalent Carbon Reinforcement Enables Fast‐Charge and Long‐Duration Lithium Storage

AbstractNiobium oxides are potential anode materials for ultrafast and safe lithium‐ion batteries due to their high ionic conductivity and relatively high operation voltage. However, the electrochemically induced phase transformations that involve multi‐electron redox reactions in a wide voltage window cause rapid capacity degradation and poor rate capability. Here, a novel carbon‐covalent amorphous niobium oxide anode is reported to greatly suppress the phase transition during cycling via formation of strong Nb─O─C bonds, achieving high‐capacity, fast‐charge and long‐duration lithium storage. This amorphous structure and forming covalent carbon contribute to good volume accommodation and high electron conductivity. The carbon‐covalent amorphous Nb2O5 displays a high reversible capacity of 361.5 mAh g−1 at 0.1 A g−1 and excellent cycling stability with a capacity of 189.8 mAh g−1 at a high rate of 10 A g−1 after 9000 cycles. Structure characterizations reveal that the well‐preserved amorphous structure without phase transition during repeated Li+ insertion/desertion is responsible for the superior performance. This work opens a new avenue on rational design of high‐performance amorphous electrode materials for next‐generation batteries.

Struktur und chemische Reaktivität von Yttrium‐stabilisierten ZrO2‐Oberflächen: Zur Bedeutung für die Wassergas‐Shift‐Reaktion

AbstractDie Oberflächenstruktur und die chemischen Eigenschaften von Yttrium‐stabilisiertem Zirkoniumdioxid (YSZ) waren in den letzten drei Jahrzehnten Gegenstand intensiver Diskussionen. Ein umfassendes Verständnis der chemischen Prozesse, die bei YSZ‐Pulvern ablaufen, ist jedoch aufgrund der fehlenden Erhebung von zuverlässigen Referenzdaten für gut kontrollierte Modellsysteme mit erheblichen Herausforderungen verbunden. Wir stellen hier die Ergebnisse aus der polarisationsaufgelösten Infrarot‐Reflexions‐Absorptions‐Spektroskopie (IRRAS) vor, die für unterschiedlich orientierte, Yttrium‐dotierte ZrO2‐Einkristalloberflächen nach der Adsorption von CO und D2O erhalten wurden. Die IRRAS‐Daten zeigen, dass die polare YSZ(100)‐Oberfläche eine Rekonstruktion erfährt, die durch eine ungewöhnliche rotverschobene CO‐Bande bei 2132 cm−1 gekennzeichnet ist. Berechnungen gemäß der Dichtefunktionaltheorie ermöglichten es, diese unerwartete Beobachtung mit unterkoordinierten Zr4+‐Kationen in der Nähe der durch die Dotierung induzierten O‐Fehlstellen in Verbindung zu bringen. Diese Rekonstruktion führt zu einer stark erhöhten chemischen Reaktivität und zu einer spontanen Dissoziation von Wasser an YSZ(100). Letzteres, eine wichtige Voraussetzung für die Katalyse der Wassergas‐Shift (WGS)‐Reaktion fehlt für YSZ(111), wo lediglich eine assoziative Adsorption beobachtet wurde. Zusammen mit einem neuartigen Analyseschema ermöglichten diese Referenzdaten eine operando‐Charakterisierung von YSZ‐Pulvern mithilfe der DRIFTS (Diffuse‐Reflexions‐Infrarot‐Fourier‐Transform‐Spektroskopie). Diese Erkenntnisse erleichtern das rationale Design und die Abstimmung von YSZ‐basierten Pulvermaterialien für katalytische Anwendungen, insbesondere für die CO‐Oxidation und die WGS‐Reaktion.

Impact of single-residue mutations on protein thermal stability: The case of threonine 83 of BC2L-CN lectin

The thermal stability of trimeric lectin BC2L-CN was investigated and found to be considerably altered when mutating residue 83, originally a threonine, located at the fucose-binding loop. Mutants were analyzed using differential scanning calorimetry and isothermal microcalorimetry. Although most mutations decreased the affinity of the protein for oligosaccharide H type 1, six mutations increased the melting temperature (Tm) by >5 °C; one mutation, T83P, increased the Tm value by 18.2 °C(T83P, Tm = 96.3 °C). In molecular dynamic simulations, the investigated thermostable mutants, T83P, T83A, and T83S, had decreased fluctuations in the loop containing residue 83. In the T83S mutation, the side-chain hydroxyl group of serine formed a hydrogen bond with a nearby residue, suggesting that the restricted movement of the side-chain resulted in fewer fluctuations and enhanced thermal stability. Residue 83 is located at the interface and near the upstream end of the equivalent loop in a different protomer; therefore, fluctuations by this residue likely propagate throughout the loop. Our study of the dramatic change in thermal stability by a single amino acid mutation provides useful insights into the rational design of protein structures, especially the structures of oligomeric proteins.

Rational Design of the Carbamazepine Ternary Cocrystals

Rational Design of the Carbamazepine Ternary Cocrystals

Recent advances in co-immobilization of organic acids and bases for cooperative and tandem catalysis

Acid–base bifunctional catalysts have been extensively used for a series of CC bond formation reactions. Among these catalysts, organic acid–base catalysts have attracted wide attention due to their structural variety, conformational dynamics, and enantioselectivity. To prevent mutual deactivation, a simple, effective, and versatile strategy is the attachment of both acid and base onto the surfaces of supports. In particular, the co-immobilization of organic acids and bases not only enhances synergistic effects in cooperative catalysis but also improves yields to desired products by controlling the diffusion of intermediates in tandem catalysis, leading to significant improvements in energy and atom efficiency. In this review, we highlight recent works addressing the broad topic of the co-immobilization of organic acids and bases for cooperative and tandem catalysis. We mainly focus on the synthetic strategies for silica-supported organic acid–base catalysts and polymer-supported organic acid–base catalysts. Furthermore, we summarize and discuss the structure–activity relationships of these catalysts. Last, the remaining issues and prospects will be discussed to advance the rational design and engineering of co-immobilized acid–base bifunctional catalysts.

Direct Catalytic Conversion of Carbon Dioxide to Liquid Hydrocarbons over Cobalt Catalyst Supported on Lanthanum(III) Ion‐Doped Cerium(IV) Oxide

Direct CO2 conversion to liquid hydrocarbons (HCs) in a single process was achieved using cobalt (Co) catalysts supported on lanthanum ion (La3+)‐doped cerium oxide (CeO2) under a gas stream of H2/CO2/N2 = 3/1/1. The yield of liquid HCs was the highest for 30 mol% of La3+‐doped CeO2, which was because extrinsic oxygen vacancy formed by doping La3+ could act as an effective reaction site for reverse water gas shift reaction. However, the excess La3+ addition afforded surface covering lanthanum carbonates, resulting in depression of the catalytic performance. On the other hand, bare CeO2 lead to an increase in the selectivity of undesirable methane, which arose from reduction of CO2 to CO proceeding by intrinsic oxygen vacancy generated by only Ce3+, and weaker CO2 capture ability of intrinsic oxygen vacancy than extrinsic one, resulting in the proceeding of Sabatier reaction on Co catalyst. The rational design of reaction sites presented in this study will contribute to sustainability.

Molten-Salt Electrochemical-Assisted Synthesis of the CeO2-OV@GC Composite-Supported Pt Clusters with a Pt-O-Ce Structure for the Oxygen Reduction Reaction.

Highly active and robust Pt-based electrocatalysts for an oxygen reduction reaction (ORR) are of crucial significance for the development of proton exchange membrane fuel cells (PEMFCs). Herein, the high-loading and well-dispersive Pt clusters on graphitic carbon-supported CeO2 with abundant oxygen vacancies (PtAC/CeO2-OV@GC) were successfully fabricated by a molten-salt electrochemical-assisted method. The bonding of Pt with the highly electronegative O induces charge redistribution through the Pt-O-Ce structure, thus reducing the adsorption energies of oxygen-containing species. Such a PtAC/CeO2-OV@GC electrocatalyst exhibits a greatly enhanced ORR performance with a mass activity of 0.41 ± 0.02 A·mg-1Pt at 0.9 V versus a reversible hydrogen electrode, which is 2.7 times the value of a commercial Pt/C catalyst and shows negligible activity decay after 20000 cycles of accelerated degradation tests. It is anticipated that this work will provide enlightening guidance on the controllable synthesis and rational design of high-performance Pt-based electrocatalysts for PEMFCs.

Accurate and efficient evaluation of the ionization potentials of extreme ultraviolet photoresists using density functionals and semi-empirical methods

Extreme ultraviolet (EUV) photoresists have become the core materials in lithography with nanometer-sized patterns and are actively explored on the path to realizing smaller critical dimensions. These photoresists can be small molecule-, polymer-, or organic–inorganic hybrid-based, with the full molecular working mechanism under investigation. For the rational design of EUV photoresists, theoretical guidance using tools like first-principle calculations and multi-scale simulations can be of great help. Considering the extremely high standard of accuracy in EUV lithography, it is critical to ensure the adoption of the appropriate methodologies in the theoretical evaluation of EUV photoresists. However, it is known that density functionals and semi-empirical methods differ in accuracy and efficiency, without a universal rule across materials. This poses a challenge in developing a reliable theoretical framework for calculating EUV photoresists. Here, we present a benchmark investigation of density functionals and semi-empirical methods on the three main types of EUV photoresists, focusing on the ionization potential, a key parameter in their microscopic molecular reactions. The vertical detachment energies (VDE) and adiabatic detachment energies (ADE) were calculated using 12 functionals, including pure functionals, hybrid functionals, Minnesota functionals, and the recently developed optimally tuned range-separated (OTRS) functionals. Several efficient semi-empirical methods were also chosen, including AM1, PM6, PM7, and GFN1-xTB in the extended tight-binding theoretical framework. These results guide the accurate and efficient calculation of EUV photoresists and are valuable for the development of multi-scale lithography protocols.Graphical

Spontaneous-Spin-Polarized 2D π-d Conjugated Frameworks Towards Enhanced Oxygen Evolution Kinetics.

Alternative strategies to design sustainable-element-based electrocatalysts enhancing oxygen evolution reaction (OER) kinetics are demanded to develop affordable yet high-performance water-electrolyzers for green hydrogen production. Here, it is demonstrated that the spontaneous-spin-polarized 2D π-d conjugated framework comprising abundant elements of nickel and iron with a ratio of Ni:Fe = 1:4 with benzenehexathiol linker (BHT) can improve OER kinetics by its unique electronic property. Among the bimetallic NiFex:y-BHTs with various ratios with Ni:Fe = x:y, the NiFe1:4-BHT exhibits the highest OER activity. The NiFe1:4-BHT shows a specific current density of 140Ag-1 at the overpotential of 350mV. This performance is one of the best activities among state-of-the-art non-precious OER electrocatalysts and even comparable to that of the platinum-group-metals of RuO2 and IrO2. The density functional theory calculations uncover that introducing Ni into the homometallic Fe-BHT (e.g., Ni:Fe = 0:1) can emerge a spontaneous-spin-polarized state. Thus, this material can achieve improved OER kinetics with spin-polarization which previously required external magnetic fields. This work shows that a rational design of 2D π-d conjugated frameworks can be a powerful strategy to synthesize promising electrocatalysts with abundant elements for a wide spectrum of next-generation energy devices.

Recent Advances in Carbon Nitride Supported Single‐Atom Catalysts: Synthesis, Characterization, and Applications for CO2 Photoreduction

AbstractPhotoreduction of CO2 into value‐added chemicals and fuels is a promising green technology for solar‐to‐chemical conversion. Owing to the atomic utilization, unique metal‐support interaction, and unsaturated coordination active sites, single‐atom catalysts (SACs) have been attracting great attention in achieving high activity and selectivity of CO2 photoreduction reactions. On the other hand, carbon nitride (C3N4) with abundant periodically unsaturated coordination of nitrogen atoms can serve as an excellent support for anchoring metal single atoms. In this context, extensive research efforts have been paid in C3N4‐based SACs for CO2 photoreduction in recent years. In this review, we report the recent advances in C3N4 supported SACs for CO2 photoreduction. We start from the introduction of synthetic strategies of various C3N4 supported metal SACs. Secondly, the main advanced characterization techniques and calculation methods for identifying the single‐atoms and their coordination environments of C3N4‐based SACs are summarized. Thirdly, some state‐of‐the‐art works on the rational design of C3N4‐based SACs and their applications in CO2 photoreduction are introduced. Lastly, we briefly summarize the main challenges and propose important perspectives of C3N4‐based SACs in CO2 photoreduction. This review is expected to provide some useful guidelines for the development of efficient and stable C3N4‐based SACs for CO2 photoreduction.

Co‐Catalytic Metal‐Support Interactions Design on Single‐Atom Alloy for Boosted Electro‐Reduction of Nitrate to Nitrogen

AbstractThe past decades have seen considerable imbalances in the nitrogen cycle due to the excessive use of nitrate in agriculture and industry. Electrocatalytic reduction of nitrate (NO3RR) to nitrogen (N2) holds significant potential for addressing nitrate pollution in wastewater but suffers from nitrite formation and the sluggish hydrogeneration process. Here a single atom alloy (SAA) catalyst featuring atomically dispersed Ru on 2D Ni metal (Ru1Ni), proving remarkable nitrate reduction performance (NO3−–N conversion (≈93%) and N2 selectivity (≈99%)) through the co‐catalytic metal‐support interactions (CMSI) effect is reported. Significantly, the Ru1Ni SAA achieves NO3RR removal capacity as high as 11.1 mg L−1 h−1 cm−2 with 20 cycles stability (9 h per cycle), surpassing most previously reported works. The core of the boosting lies in the synergistically promoted nitrate activation and accelerated hydrogenation of nitrogen oxide intermediates on the Ru site and Ni substrate, respectively, revealed by various in situ experiments and theoretical simulations. DFT calculations indicate electron transfer from substrate Ni to Ru and more robust interaction between NO3− and Ru–Ni in comparison to that of Ni–Ni. This work offers a resilient methodology for the rational design of highly efficient electrocatalysts with CMSI modulation for NO3RR, illuminating the arena of wastewater treatment and the nitrogen cycle.

Rational Design of Coumarin-Based Hybridized Local and Charge-Transfer Blue Emitters for Solution-Processed Organic Light-Emitting Diodes.

Hybridized local and charge-transfer (HLCT) with the utilization of both singlet and triplet excitons through the "hot excitons" channel have great application potential in highly efficient blue organic light-emitting diodes (OLEDs). The proportion of charge-transfer (CT) and locally excited (LE) components in the relevant singlet and triplet states makes a big difference for the high-lying reverse intersystem crossing process. Herein, three novel donor (D)-acceptor (A) type HLCT materials, 7-([1,1'-biphenyl]-4-yl(9,9-dimethyl-9H-fluoren-2-yl)amino)-3-phenyl-1H-isochromen-1-one (pPh-7P), 7-([1,1'-biphenyl]-4-yl(9,9-dimethyl-9H-fluoren-2-yl)amino)-3-methyl-1H-isochromen-1-one (pPh-7M), and 6-([1,1'-biphenyl]-4-yl(9,9-dimethyl-9H-fluoren-2-yl)amino)-3-methyl-1H-isochromen-1-one (pPh-6M), were rationally designed and synthesized with diphenylamine derivative as donor and oxygen heterocyclic coumarin moiety as acceptors. The proportions of CT and LE components were fine controlled by changing the connection site of diphenylamine derivative at C6/C7-position and the substituent at C3-position of coumarin moiety. The HLCT characteristics of pPh-7P, pPh-7M, and pPh-6M were systematically demonstrated through photophysical properties and density functional theory calculations. The solution-processed doped OLEDs based on pPh-6M exhibited deep-blue electroluminescence with the maximum emission wavelength of 446 nm, maximum luminance of 8755 cd m-2, maximum current efficiency of 5.83 cd A-1, and maximum external quantum efficiency of 6.54 %. The results reveal that pPh-6M with dominant 1LE and 3CT components has better OLED performance.

Metal polyphenol network structure regulated Fe2O3-CeO2/PC for the enhanced electro-Fenton-like remediation of organic wastewater in a widely applicable pH range

Developing efficient Fenton and Fenton-like systems for the remediation of organic wastewater remains a challenge for the limited applicable pH range and sluggish kinetics. In this study, a novel electro-Fenton-like system was constructed for the efficient degradation of multiple organic pollutants based on Fe-Ce bimetallic oxide supported on porous carbon (Fe2O3-CeO2/PC) heterogeneous catalyst, which was prepared by annealing metal polyphenol network structure (MPNs) regulated Fe-Ce-tannic acid (TA) complexes. The Fe2O3-CeO2/PC-based system showed higher removal rate (93.6 %) and apparent rate constant (0.021 min−1) for tetracycline (TC) as compared to the MPNs-free Fe2O3-CeO2 system (79.1 %, 0.011 min−1), catalyst-free system (59.3 %, 0.007 min−1) and adsorption system (66.7 %, 0.009 min−1). Under the optimal conditions, the as-proposed electro-Fenton system showed a high removal rate of ∼ 95 % to the typical phenol, dye and antibiotics. After 240 min’ electrolysis, the removal rates of COD and TOC reached 93.7 % and 58.7 %, respectively. After 5 cycles’ degradation, the removal rate of TC didn’t show obvious decline in performance (remained at about ∼ 90 %). More importantly, the system can effectively remove TC in simulated wastewater in a broad pH range of 3–11, which was much superior to the other electro-Fenton-like systems. The satisfactory degradation performance of the electro-Fenton-like system based on MPNs-regulated Fe2O3-CeO2/PC was attributed to the strong coordination ability between TA and the metal species in the heterogeneous catalyst and the bimetallic synergistic effect on optimizing the electronic configuration of Fe2O3-CeO2/PC, which accelerated the redox cycles of ≡TA-Fe(Ⅲ)/≡TA-Fe(II) and ≡TA-Ce(Ⅳ)/≡TA-Ce(III) as electron shuttles and facilitated the production of sufficient ROS (mainly O2·− and 1O2) for the degradation and mineralization of the organic pollutants. Based on the produced intermediates, the feasible degradation pathways of the representative TC occurred in Fe2O3-CeO2/PC-based electro-Fenton-like system were inferred. This work lays an important theoretical foundation for the rational design of high-performance electrocatalysts and electro-Fenton/electro-Fenton-like systems, enabling the efficient remediation of organic wastewater.

Internal electric field-modulated dual S-scheme ZnO@Co3O4/CsPbBr3 nanocages for highly active and selective photocatalytic CO2 reduction

The rational design of a step-scheme (S-scheme) heterojunction with strong internal electric field (IEF) and high redox capacity is a promising strategy for photocatalytic CO2 reduction reaction (CO2RR). However, the precise process of charge transport on the multi-interfaces remains a great challenge. Herein, a dual S-scheme heterojunction constructed in the ZnO@Co3O4/CsPbBr3 hierarchical nanocage was prepared for enhancing CO2RR activity. Without sacrificial agent and photosensitizer, the optimal photocatalyst exhibits a competitive CH4 yield rate of 238.8 μmol g−1h−1 with high selectivity (90.9%), affording an apparent quantum efficiency of 4.6 % at 400 nm, outperforming most previously comparable photocatalysts. In situ X-ray photoelectron spectroscopy (in situ XPS), photoelectrochemical measurement and theoretical calculation verifies the dual S-schematic charge-transport pathway. The remarkably improved performance in CO2RR is due to the rapid charge separation through O-Co-Br bridge driven by the strong internal electric field. This research furnishes a new insight to reveal dynamic charge transfer mechanism for CO2 conversion applications.

Unraveling the Dynamic Molecular Motions of a Twin‐Cavity Cage with Slow Configurational but Rapid Conformational Interconversions

AbstractFeaturing diverse structural motions/changes, dynamic molecular systems hold promise for executing complex tasks. However, their structural complexity presents formidable challenge in elucidating their kinetics, especially when multiple structural motions are intercorrelated. We herein introduce a twin‐cavity cage that features interconvertible C3‐ and C1‐configurations, with each configuration exhibiting interchangeable P‐ and M‐conformations. This molecule is therefore composed of four interconnected chiral species (P)‐C3, (M)‐C3, (P)‐C1, (M)‐C1. We showcase an effective approach to decouple these sophisticated structural changes into two kinetically distinct pathways. Utilizing time‐dependent 1H NMR spectroscopy at various temperatures, which disregards the transition between mirror‐image conformations, we first determine the rate constant (kc) for the C3‐ to C1‐configuration interconversion, while time‐dependent circular dichroism spectroscopy at different temperatures quantifies the observed rate constant (kobs) of the ensemble of all the structural changes. As kobs kc, it allows us to decouple the overall molecular motions into a slow configurational transformation and rapid conformational interconversions, with the latter further dissected into two independent conformational interchanges, namely (P)‐C3 (M)‐C3 and (P)‐C1 (M)‐C1. This work, therefore, sheds light on the comprehensive kinetic study of complex molecular dynamics, offering valuable insights for the rational design of smart dynamic materials for applications of sensing, separation, catalysis, molecular machinery, etc.

Unraveling the Dynamic Molecular Motions of a Twin-Cavity Cage with Slow Configurational but Rapid Conformational Interconversions.

Featuring diverse structural motions/changes, dynamic molecular systems hold promise for executing complex tasks. However, their structural complexity presents formidable challenge in elucidating their kinetics, especially when multiple structural motions are intercorrelated. We herein introduce a twin-cavity cage that features interconvertible C3- and C1-configurations, with each configuration exhibiting interchangeable P- and M-conformations. This molecule is therefore composed of four interconnected chiral species (P)-C3, (M)-C3, (P)-C1, (M)-C1. We showcase an effective approach to decouple these sophisticated structural changes into two kinetically distinct pathways. Utilizing time-dependent 1H NMR spectroscopy at various temperatures, which disregards the transition between mirror-image conformations, we first determine the rate constant (kc) for the C3- to C1-configuration interconversion, while time-dependent circular dichroism spectroscopy at different temperatures quantifies the observed rate constant (kobs) of the ensemble of all the structural changes. As kobs kc, it allows us to decouple the overall molecular motions into a slow configurational transformation and rapid conformational interconversions, with the latter further dissected into two independent conformational interchanges, namely (P)-C3 (M)-C3 and (P)-C1 (M)-C1. This work, therefore, sheds light on the comprehensive kinetic study of complex molecular dynamics, offering valuable insights for the rational design of smart dynamic materials for applications of sensing, separation, catalysis, molecular machinery, etc.

Rational design of the binder-free polythiophene nanofibers deposited nickel foam for the high-performance aqueous asymmetric supercapacitor

Development of the binder-free electrode materials and employing in the supercapacitor is the essential footstep for high energy storage. The present study highlights the cost-effective synthesis strategy for the binder-free growth of the amorphous polythiophene nanofibers over the nickel foam substrate. The presence of functional bonds like CC, C-H, and C-S has confirmed the deposition of the polythiophene nanofibers on the nickel foam, while elemental mapping analysis detected the uniform distribution of Carbon and Sulfur elements over nanofibers. The surface structure of the polythiophene is transformed from nanofibers to a wire-like structure as the result of the monomer concentration variation. The optimized polythiophene film exhibited the highest areal capacitance of 1263.2 mF/cm2 at 2 mA/cm2 with 90.03% capacitance retention after 5000 cycles. Moreover, the aqueous asymmetric device (PTh//AC) is fabricated which delivered 31.5 F/g at 10 mA/cm2. The highest specific energy of PTh//AC device was 6.3 Wh/kg. Also, it showed good retention capability with 82.3% retention. Based on these results, the present investigation provides the performance metrics of the polythiophene nanofibers and highlights the potential utilization of the polythiophene-based supercapacitor in practical energy storage systems.