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First-principles calculations within the density functional theory (DFT) framework have been performed in order to investigate various conformations of the 2,5-pyridine di-carboxylic acid (PDCA) molecule adsorbed onto the Cu(011) surface. By means of DFT calculations the adsorption geometry, the bond formation and the electronic properties of PDCA molecule conformations on the Cu(011) surface have been studied. The most important structural property is the orientation of the COOH H atom which can point either toward the aromatic ring or toward the vacuum. This H atom position determines the possible reactions in which the adsorbed molecule can get involved and also has a significant impact on the value of the Cu-molecule system work function. Thus, we find that simply by changing the H atom orientation (from up to down) the Cu-molecule system work function can be varied with more than 2.5 eV. This is a significant result as a lot of effort is put nowadays in finding efficient ways for the in situ variation of the systems work function. Scanning tunneling microscopy (STM) images, reflexion absorption infrared vibrational spectra (RAIRS) as well as various thermodynamic properties (adsorption entropies, enthalpies) have also been investigated in order to get a better insight into the system studied and to provide support to possible experimental studies (STM or RAIRS experiments). [ABSTRACT FROM AUTHOR]

A new method, non-Markovian quantum-classical approximation (NQCA), is suggested to model the photoisomerization of polyatomic molecules. The NQCA method can be successfully applied to follow the photoisomerization process for a wide class of reacting systems, namely, those for which the time scale required for the equilibration in the phase space of the potential energy surface (PESs) is short compared to the time scale of the transitions between them. Such a situation is quite typical for the nonadiabatic transitions between the different electronic states in polyatomic molecules, where a high density of vibronic states facilitates the intramolecular vibrational energy redistribution, thus providing an efficient relaxation for the phase space distribution. The NQCA can easily be combined with molecular dynamics and quantum-chemical methods to describe the evolution of the classical degrees of freedom and the quantum part of the problem. [ABSTRACT FROM AUTHOR]

Hot absorption spectra of polyatomic molecules may exhibit a characteristic shoulder. Its origin and connection to the 0-0 transition energy gap has been established on the basis of a recently developed quantum-classical approach. We demonstrate that an accurate estimate of the transition energy can be obtained directly from experimental data. The method can be used to study the solvent influence on the energetics of electronic transitions. [ABSTRACT FROM AUTHOR]

The present paper describes the dynamics of hexane cracking in ZSM-5 and methanol oxidation on vanadium beta zeolite (V-BEA) by means of ab-initio Molecular Dynamics (AIMD) and transition path sampling (TPS). [ABSTRACT FROM AUTHOR]

N-, C-, O-, S-coordinated single-metal-sites (SMSs) have garnered significant attention due to the potential for significantly enhanced catalytic capabilities resulting from charge redistribution. However, significant challenges persist in the precise design of well-defined such SMSs, and the fundamental comprehension has long been impeded in case-by-case reports using carbon materials as investigation targets. In this work, the well-defined molecular catalysts with N 3 C 1 -anchored SMSs, i.e., N-confused metalloporphyrins (NCPor-Ms), are calculated for their catalytic oxygen reduction activity. Then, NCPor-Ms with corresponding N 4 -anchored SMSs (metalloporphyrins, Por-Ms), are synthesized for catalytic activity evaluation. Among all, NCPor-Co reaches the top in established volcano plots. NCPor-Co also shows the highest half-wave potential of 0.83 V vs. RHE, which is much better than that of Por-Co (0.77 V vs. RHE). Electron-rich, low band gap and regulated d-band center contribute to the high activity of NCPor-Co. This study delves into the examination of well-defined asymmetric SMS molecular catalysts, encompassing both theoretical and experimental facets. It serves as a pioneering step towards enhancing the fundamental comprehension and facilitating the development of high-performance asymmetric SMS catalysts., (© 2023 Wiley-VCH GmbH.)

Ammonia is a key chemical feedstock worldwide. Compared with the well-known Haber-Bosch method, electrocatalytic nitrogen reduction reaction (ENRR) can eventually consume less energy and have less CO 2 emission. In this study, a plasma-enhanced chemical vapor deposition method is used to anchor transition metal element onto 2D conductive material. Among all attempts, Ru single-atom and Ru-cluster-embedded perovskite oxide are discovered with promising electrocatalysis performance for ENRR (NH 3 yield rate of up to 137.5 ± 5.8 µg h -1  mg cat -1 and Faradaic efficiency of unexpected 56.9 ± 4.1%), reaching the top record of Ru-based catalysts reported so far. In situ experiments and density functional theory calculations confirm that the existence of Ru clusters can regulate the electronic structure of Ru single atoms and decrease the energy barrier of the first hydrogenation step (*NN to *NNH). Anchoring Ru onto various 2D perovskite oxides (LaMO-Ru, MCr, Mn, Co, or Ni) also show boosted ENRR performance. Not only this study provides an unique strategy toward transition-metal-anchored new 2D conductive materials, but also paves the way for fundamental understanding the correlation between cluster-involved single-atom sites and catalytic performance., (© 2023 Wiley-VCH GmbH.)

Covalent triazine frameworks (CTFs) are among the most valuable frameworks owing to many fantastic properties. However, molten salt-involved preparation of CTFs at 400-600 °C causes debate on whether CTFs represent organic frameworks or carbon. Herein, new CTFs based on the 1,3-dicyanoazulene monomer (CTF-Azs) are synthesized using molten ZnCl 2 at 400-600 °C. Chemical structure analysis reveals that the CTF-Az prepared at low temperature (400 °C) exhibits polymeric features, whereas those prepared at high temperatures (600 °C) exhibit typical carbon features. Even after being treated at even higher temperatures, the CTF-Azs retain their rich porosity, but the polymeric features vanish. Although structural de-conformation is a widely accepted outcome in polymer-to-carbon rearrangement processes, the study evaluates such processes in the context of CTF systems. A proof-of-concept study is performed, observing that the as-synthesized CTF-Azs exhibit promising performance as cathodes for Li- and K-ion batteries. Moreover, the as-prepared NPCs exhibit excellent catalytic oxygen reduction reaction (ORR) performance; hence, they can be used as air cathodes in Zn-air batteries. This study not only provides new building blocks for novel CTFs with controllable polymer/carbon features but also offers insights into the formation and structure transformation history of CTFs during thermal treatment., (© 2022 Wiley-VCH GmbH.)

The electrochemical reduction of carbon dioxide (CO 2 ) based on molecular catalysts has attracted more attention, owing to their well-defined active sites and rational structural design. Metal porphyrins (PorMs) have the extended π-conjugated backbone with different transition metals, endowing them with unique CO 2 reduction properties. However, few works focus on the investigation of symmetric architecture of PorMs as well as their aggregation behavior to CO 2 reduction. In this work, a series of Co II porphyrins (PorCos) with symmetric and asymmetric substituents were used as model of molecular catalysts for CO 2 reduction. Owing to the electron donating effect of 2,6-dimethylbenzene (DMB), bandgaps of the complexes became narrower with the increasing number of DMB. As electrocatalysts, all PorCos exhibited promising electrocatalytic CO 2 reduction performance. Among the three molecules, asymmetric Co II porphyrin (as-PorCo) showed the lowest onset potential of -288 mV and faradaic efficiencies exceeding 93 % at -0.6 V vs. reversible hydrogen electrode, which is highly competitive among the reported state-of-art porphyrin-based electrocatalysts. The CO 2 reduction performance depended on π-π stacking between PorCo with carbon nanotubes (CNTs) and adjacent PorCos, which could be readily controlled by atomically positioned DMB in PorCo. Density functional theory calculations also suggested that the charge density between PorCo and CNT was highest due to the weak steric hindrance in as-PorCo, providing the new insight into molecular design of catalysts for efficient electrochemical CO 2 reduction., (© 2022 Wiley-VCH GmbH.)

The electronic properties of two-dimensional semiconductors can be strongly modulated by interfacing them with atomically precise self-assembled molecular lattices, yielding hybrid van der Waals heterostructures (vdWHs). While proof-of-concepts exploited molecular assemblies held together by lateral unspecific van der Waals interactions, the use of 2D supramolecular networks relying on specific non-covalent forces is still unexplored. Herein, prototypical hydrogen-bonded 2D networks of cyanuric acid (CA) and melamine (M) are self-assembled onto MoS 2 and WSe 2 forming hybrid organic/inorganic vdWHs. The charge carrier density of monolayer MoS 2 exhibits an exponential increase with the decreasing area occupied by the CA·M unit cell, in a cooperatively amplified process, reaching 2.7 × 10 13  cm -2 and thereby demonstrating strong n-doping. When the 2D CA·M network is used as buffer layer, a stark enhancement in the catalytic activity of monolayer MoS 2 for hydrogen evolution reactions is observed, outperforming the platinum (Pt) catalyst via gate modulation., (© 2022. The Author(s).)

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have been extensively investigated during the last two decades. More recently, a family of hybrid materials ( i.e. , MOF@COF) has emerged as particularly appealing for gas separation and storage, catalysis, sensing, and drug delivery. MOF@COF hybrids combine the unique characteristics of both MOF and COF components and exhibit peculiar properties including high porosity and large surface area. In this work, we show that the infiltration of redox-active 7,7,8,8-tetracyanoquinodimethane (TCNQ) molecules into the pores of MOF@COF greatly improves the characteristics of the latter, thereby attaining high-performance energy storage devices. Density functional theory (DFT) calculations were employed to guide the design of a MOF@COF-TCNQ hybrid with the TCNQ functional units incorporated in the pores of MOF@COF. To demonstrate potential application of our hybrids, the as-synthesized MOF@COF-TCNQ hybrid has been employed as an active material in supercapacitors. Electrochemical energy storage analysis revealed outstanding supercapacitor performance, as evidenced by a specific areal capacitance of 78.36 mF cm -2 and a high stack volumetric energy density of 4.46 F cm -3 , with a capacitance retention of 86.4% after 2000 cycles completed at 0.2 A cm -2 . DFT calculation results strongly indicate that the high capacitance of MOF@COF-TCNQ has a quantum capacitance origin. Our liquid-phase infiltration protocol of MOF@COF hybrids with redox-active molecules represents a efficacious approach to design functional porous hybrids.

Developing effective electrocatalysts for the oxygen reduction reaction is of great significance for clean and renewable energy technologies, such as metal-air batteries and fuel cells. Defect engineering is the central focus of this field because the overall catalytic performance crucially depends on highly active defects. For the ORR, topological defects have been proven to have a positive effect. However, because preparation and characterization of such defects are difficult, a basic understanding of the relationship between topological defects and catalytic performance remains elusive. In this study, topological defect-containing Fe/N co-doped mesoporous carbon nanosheets were synthesized using azulene-based sandwich-like polymer nanosheets as the precursor. As electrocatalysts, such porous carbon nanosheets exhibited promising ORR activity, methanol tolerance ability, and stability with a half-wave potential of 841 mV under alkaline conditions, which is superior to those of most of the reported porous carbons. As the air cathode for Zn-air batteries, the catalyst exhibited a peak power density of 153 mW cm -2 and a specific capacity of 628 mA h g -1 ,which were higher than those of a Pt/C-based Zn-air battery. Density functional theory calculation further proved the positive effect of topological defects on the oxygen reduction activity. These results indicate that bottom-up topological defect engineering could be a new and promising strategy for developing high-performance electrocatalysts.

Coordination polymer frameworks (CPFs) have broad applications due to their excellent features, including stable structure, intrinsic porosity, and others. However, preparation of thin-film CPFs for energy storage and conversion remains a challenge because of poor compatibility between conductive substrates and CPFs and crucial conditions for thin-film preparation. In this work, a CPF film was prepared by the coordination of the anisotropic four-armed ligand and Cu II at the liquid-liquid interface. Such film-based micro-supercapacitors (MSCs) are fabricated through high-energy scribing and electrolytes soaking. As-fabricated MSCs displayed high volumetric specific capacitance of 121.45 F cm -3 . Besides, the volumetric energy density of MSCs reached 52.6 mWh cm -3 , which exceeds the electrochemical performance of most reported CPF-based MSCs. Especially, the device exhibited alternating current (AC) line filtering performance (-84.2° at 120 Hz) and a short resistance capacitance (RC) constant of 0.08 ms. This work not only provides a new CPF for MSCs with AC line filtering performance but also paves the way for thin-film CPFs preparation with versatile applications., (© 2021 Wiley-VCH GmbH.)

Among various organic cathode materials, C═O group-enriched structures have attracted wide attention worldwide. However, small organic molecules have long suffered from dissolving in electrolytes during charge-discharge cycles. π-Conjugated microporous polymers (CMPs) become one solution to address this issue. However, the synthesis strategy for CMPs with rich C═O groups and stable backbones remains a challenge. In this study, a novel CMP enriched with C═O units was synthesized through a highly efficient Diels-Alder reaction. The as-prepared CMP exhibited a fused carbon backbone and a semiconductive characteristic with a band gap of 1.4 eV. When used as an organic electrode material in LIBs, the insoluble and robust fused structure caused such CMPs to exhibit remarkable cycling stability (a 96.1% capacity retention at 0.2 A g -1 after 200 cycles and a 94.8% capacity retention at 1 A g -1 after 1500 cycles), superior lithium-ion diffusion coefficient (5.30 × 10 -11 cm 2 s -1 ), and excellent rate capability (95.8 mAh g -1 at 1 A g -1 ). This study provided a novel synthetic method for fabricating quinone-enriched fused CMPs, which can be used as LIB cathode materials.

Microsupercapacitors (MSCs) have drawn great attention for use as miniaturized electrochemical energy storage devices in portable, wearable, as well as implantable electronics. Many materials have been developed as electrodes for MSCs. However, the thin-film fabrication for most of these materials involves multistep operations, including filtration, spray coating, and sputtering. Most importantly, these methods present challenges for the preparation of thin films at the atomic or molecular scale. Therefore, the understanding of performance of ultrathin-film-based MSCs remains challenge. Herein, a B/N-enriched polymer film is successfully prepared using the photoassisted interfacial approach. The as-synthesized polymer film exhibits typical semiconductive characteristics and can be easily scaled up to a large area of up to tens of square centimeters. This ultrathin polymer film can be directly transferred to silicon wafers to fabricate MSC through laser scribing. The prepared MSC exhibits specific volumetric capacitance as high as 20.9 F cm -3 , corresponding to volumetric energy density of 2.9 mWh cm -3 (at 0.1 V s -1 ). Moreover, the volumetric power density can reach 1461 W cm -3 , surpassing most existing semiconductive polymer film-based MSC devices. In addition, the prepared MSC exhibits typical AC line-filtering ability (-67° at 120 Hz). This study offers a facile interfacial approach to preparing semiconductive polymer films with aromatic moieties for microsized energy storage devices.

Heterostructures exhibit considerable potential in the field of energy conversion due to their excellent interfacial charge states in tuning the electronic properties of different components to promote catalytic activity. However, the rational preparation of heterostructures with highly active heterosurfaces remains a challenge because of the difficulty in component tuning, morphology control, and active site determination. Herein, a novel heterostructure based on a combination of RuMo nanoalloys and hexagonal N-doped carbon nanosheets is designed and synthesized. In this protocol, metal-containing anions and layered double hydroxides are employed to control the components and morphology of heterostructures, respectively. Accordingly, the as-made RuMo-nanoalloys-embedded hexagonal porous carbon nanosheets are promising for the hydrogen evolution reaction (HER), resulting in an extremely small overpotential (18 mV), an ultralow Tafel slope (25 mV dec -1 ), and a high turnover frequency (3.57 H 2 s -1 ) in alkaline media, outperforming current Ru-based electrocatalysts. First-principle calculations based on typical 2D N-doped carbon/RuMo nanoalloys heterostructures demonstrate that introducing N and Mo atoms into C and Ru lattices, respectively, triggers electron accumulation/depletion regions at the heterosurface and consequently reduces the energy barrier for the HER. This work presents a convenient method for rational fabrication of carbon-metal heterostructures for highly efficient electrocatalysis., (© 2020 Wiley-VCH GmbH.)

Molybdenum carbide (Mo 2 C) based catalysts were found to be one of the most promising electrocatalysts for hydrogen evolution reaction (HER) in acid media in comparison with Pt-based catalysts but were seldom investigated in alkaline media, probably due to the limited active sites, poor conductivity, and high energy barrier for water dissociation. In this work, Mo 2 C-embedded nitrogen-doped porous carbon nanosheets (Mo 2 C@2D-NPCs) were successfully achieved with the help of a convenient interfacial strategy. As a HER electrocatalyst in alkaline solution, Mo 2 C@2D-NPC exhibited an extremely low onset potential of ∼0 mV and a current density of 10 mA cm -2 at an overpotential of ∼45 mV, which is much lower than the values of most reported HER electrocatalysts and comparable to the noble metal catalyst Pt. In addition, the Tafel slope and the exchange current density of Mo 2 C@2D-NPC were 46 mV decade -1 and 1.14 × 10 -3 A cm -2 , respectively, outperforming the state-of-the-art metal-carbide-based electrocatalysts in alkaline media. Such excellent HER activity was attributed to the rich Mo 2 C/NPC heterostructures and synergistic contribution of nitrogen doping, outstanding conductivity of graphene, and abundant active sites at the heterostructures.

One of the key challenges in two-dimensional (2D) materials is to go beyond graphene, a prototype 2D polymer (2DP), and to synthesize its organic analogues with structural control at the atomic- or molecular-level. Here we show the successful preparation of porphyrin-containing monolayer and multilayer 2DPs through Schiff-base polycondensation reaction at an air-water and liquid-liquid interface, respectively. Both the monolayer and multilayer 2DPs have crystalline structures as indicated by selected area electron diffraction. The monolayer 2DP has a thickness of∼0.7 nm with a lateral size of 4-inch wafer, and it has a Young's modulus of 267±30 GPa. Notably, the monolayer 2DP functions as an active semiconducting layer in a thin film transistor, while the multilayer 2DP from cobalt-porphyrin monomer efficiently catalyses hydrogen generation from water. This work presents an advance in the synthesis of novel 2D materials for electronics and energy-related applications.