Metal-organic frameworks (MOFs) show significant potential for addressing the urgent demand for high-efficiency carbon dioxide (CO2) capture and conversion. However, gaining mechanistic insights into CO2 diffusion processes and host-guest interactions within MOFs remains largely unexplored, due to the challenges associated with atomic-scale imaging. Here, we directly visualize the binding configurations of CO2 molecules and their dynamic evolution in real space and real time within surface-confined MOFs by combining in situ CO2 dosing with atomic-resolution scanning probe microscopy. Bond-resolved imaging reveals two distinct CO2 adsorption configurations, arising from the interactions between flat adsorbed CO2 and ligand/metal coordination sites of MOFs. Well-organized CO2 patterns composed of alternating triangular and rhombic subunits are clearly identified within the MOF pores. Temperature-dependent measurements further identify characteristic regimes associated with early stages of CO2 capture, diffusion, and release. Furthermore, we show how a sudden increase of CO2 concentration would cause the instability and even collapse of MOFs. These observations highlight the dynamic and nonequilibrium nature of CO2 capture in surface-confined MOFs and demonstrate the power of real-space approaches for elucidating gas adsorption and diffusion mechanisms at the molecular scale.

O2 adsorption is pivotal in O2-involved catalytic processes, where catalysts' spin properties play crucial roles, yet the microscopic mechanisms remain elusive. Here, scanning tunneling microscopy/spectroscopy and atomic force microscopy characterizations enable direct comparison of O2 affinity between the high-spin (NiH) and low-spin (NiL) Ni centers alternately embedded in the coordination chains on Au(111) at the atomic scale, revealing preferred O2 adsorption at NiH. Density functional theory studies demonstrate that this selectivity arises from the distinct d-electron configurations of NiH and NiL, which significantly affect the O2-Ni hybridization. The stronger O2 adsorption at NiH than at NiL drives a spin transition of NiL upon O2 adsorption, which could be kinetically unfavorable and thus further contribute to the observed selective O2-NiH binding. These findings offer microscopic insights into the spin-modulated O2 adsorption.

We investigate the self-assembly behavior of the prototypical aggregation induced emission (AIE) luminogen tetraphenylethene (TPE) on the Ag(111) surface. Thermally evaporated TPE molecules form a highly ordered, close-packed monolayer, as resolved by scanning tunneling microscopy (STM). The symmetric, non-planar conformation of TPE facilitates molecule-substrate interactions and intermolecular π-π stacking. Annealing at 60 °C preserved the structural integrity and molecular composition but induced a ∼15° tilt in the assembly orientation, attributed to thermally activated reorganization of interfacial bonds on substrate interactions. STM imaging combined with ball-and-stick modeling elucidated the molecular arrangement and identified localized bright spots as electronic signatures of the phenyl ring orientation. These results demonstrate substrate-directed assembly mechanisms relevant to designing AIE materials.

Two-dimensional conjugated polymers (2DCPs) are significant macromolecular materials with intriguing and tunable physicochemical properties that depend on their geometries. Graphdiyne and its derivatives are exemplary 2DCPs featuring sp-sp2 hybridized skeletons. However, achieving single-layered, large-domain/regular graphdiyne and its derivatives on surfaces remains a formidable challenge due to the lack of selective 2D covalent polymerization methods. Here, we report a selective on-surface 2D covalent polymerization method via the combination of cobalt catalysis and coronene templating, achieving the synthesis of single-layered fluorographdiyne nanosheets up to 60*60 nm2 on Au(111) surface. Using scanning probe techniques, we visualize the sequential polymerization process and characterize cobalt-activated coupling intermediates at the atomic level. Experimental and theoretical analyses suggest that strong d-π coupling between cobalt and alkynyl transforms a robust Csp-Au bond into a weaker Csp2-Au bond, thereby facilitating the demetallization C-C coupling. Besides, the templating effect of coronene suppresses kinetically trapped defects and improves the selectivity of hexagonal-ring formation in the complex 2D covalent polymerization process.

Herein, we report a novel photocatalytic strategy for the intermolecular cyclopropanation of olefins with brominating agents. This protocol not only overcomes steric hindrance but also enables the incorporation of fluorine atoms into the three-membered cyclopropane ring, concomitantly constructing two quaternary carbon centers. Notably, the developed strategy exhibits a broad substrate scope and an excellent functional group tolerance. Furthermore, its synthetic utility is exemplified by the successful late-stage cyclopropanation of structurally complex molecules and drug derivatives, highlighting its potential for practical applications in organic synthesis and medicinal chemistry.

Perovskite solar cells (PSCs) have emerged as a promising photovoltaic technology due to their exceptional power conversion efficiencies (PCEs) and cost-effective manufacturing protocols. However, persisting challenges related to the perovskite active-layer film quality, defect density profiles and long-term stabilities continue to hinder their commercial viability. In this study, we introduced a novel resonance-structured ionic additive (PPNCl) into the perovskite precursor solution to strategically regulate the perovskite crystallization process and passivate surface defects of the perovskite crystals. The coexistence of two charged resonance forms of the [PPN](+) cations enables strong chemical interactions with the perovskite components, retarding the perovskite crystallization kinetics to achieve enhanced crystallinity and reduced residual lattice strain of the perovskite films. Furthermore, the excellent hydrophobicity of the [PPN](+) cations endows the perovskite films and solar cells with outstanding moisture tolerance. As a result, the PPNCl-based PSCs demonstrate a champion PCE of 25.30 % and exhibit significantly improved device stabilities, retaining 82.2 % of the initial efficiency after aging for 700 h under air conditions.

Sodium-ion batteries have emerged as promising alternatives to lithium-ion batteries due to their abundant raw material reserves, low cost, enhanced safety, and environmental sustainability. Na2Fe2OS2, featuring a layered anti-perovskite structure, has attracted significant interest for its high capacity and facile synthesis. In this study, density functional theory calculations were performed to systematically investigate the phase stability, ionic conductivity, and voltage characteristics of Na2Fe2OS2 as a model system for anti-perovskite layered cathode materials. The compound exhibits excellent phase stability, and its equilibrium potential was calculated for the series Na(x)Fe(2)OCh(2) (0 < x < 2) (where Ch represents chalcogenides). Na ion transport analysis using the climbing image nudged elastic band method reveals a relatively low migration barrier (similar to 0.47 eV) along a diagonal pathway, indicating efficient Na+ mobility. To expand the materials design space, we systematically explored the effects of substituting Fe with various transition metals and replacing S with Se in Na(2)TM(2)OCh(2) structures. Among the variants studied, Na2Mn2OS2 demonstrates the most favorable combination of high voltage (similar to 2.51 V), robust phase stability, and superior energy density (similar to 427 W & sdot;h/kg). This comprehensive comparison of transition metal substitutions provides valuable insights for the rational design and experimental development of next-generation anti-perovskite layered cathode materials for sodium-ion batteries.

Herein, we have demonstrated a pathway regulation of a stepwise reaction on Cu(111), including both debrominative and dehydrogenative couplings, facilitated by a persistent template effect from the metal-organic coordination motif of Cu-N. Using scanning tunneling microscopy, in combination with density functional theory calculations, we revealed that the compound 2-bromo-1,8-naphthyridine on Cu(111) initially transformed into C-Cu organometallic dimeric intermediates via dehalogenation, and then into covalent tetramers and cyclic pentamers via dehydrogenation upon successive thermal annealing treatments. The cisoid species was predominant in all reaction steps, demonstrating the persistent template effect of Cu-N coordination. Our results present a new opportunity to precisely control stepwise on-surface reactions, potentially enabling the bottom-up engineering of functional organic nanostructures.

Understanding the mechanism of methanol oxidation reaction (MOR) remains a challenge in the development of direct methanol fuel cells. Large-scale investigations of the MOR encounter issues related to mass transfer and averaging effects. To address these limitations, exploring the MOR on the surfaces of individual nanocatalyst and precisely identifying the reaction steps can yield valuable insights into the underlying pathways. In this study, we employed in situ nanoplasmonic resonance scattering spectroscopy to dynamically monitor the MOR process on single gold nanorod particles (GNPs) and Pt-coated gold nanoparticles (Pt-GNPs). We observed the evolution of metal hydroxides, which was assumed as the active species. Notably, the dynamic behavior of the surface atomic layers revealed the rate-determining steps for both the GNPs and Pt-GNPs, indicating competitive adsorption of intermediates on the nanocatalyst surface. The resulting inherent reaction mechanism highlights the thermodynamics-dependent catalysts’ redox processes and their surface adsorptions, which holds significance for advancing highly active MOR catalysts.

Recent findings regarding spin-orbit torques (SOTs) and current-induced magnetization switching in ferromagnetic (FM) single layers have attracted substantial attention due to the advantage of not necessitating the use of heavy-metal layers. Nevertheless, despite prior studies on the interior structural engineering of the SOT, the external techniques for manipulating the SOT in the FM single layer remains elusive, which is indispensable for the practical application of the single layer SOT devices. Here, we demonstrate external manipulation of SOT generation in CoPd single layer through the fabrication of CoPd film with a composition gradient, utilizing the H2-absorption property of Pd. It is found that the H-induced strain within the CoPd film plays a pivotal role in generating SOT. Meanwhile, we demonstrate that the critical current density required for the current-induced magnetization switching is markedly diminished with the application of H2 due to the enhanced SOT generation and reduced perpendicular magnetic anisotropy energy. Our findings offer a straightforward method for external manipulation of single layer SOT devices, and hold the potential for applications of the spintronic devices.

The issue of energy scarcity has become more prominent due to the recent scientific and technological advancements. Consequently, there is an urgent need for research on sustainable and renewable resources. Solar energy, in particular, has emerged as a highly promising option because of its pollution-free and environment-friendly characteristics. Among the various solar energy technologies, perovskite solar cells have attracted much attention due to their lower cost and higher photoelectric conversion efficiency (PCE). However, the inherent instability of perovskite materials hinders the commercialization of such devices. The utilization of scanning tunneling microscopy/spectroscopy (STM/STS) can provide valuable insights into the fundamental properties of different perovskite materials at the atomic scale, which is crucial for addressing this challenge. In this review, we present the recent research progress of STM/STS analysis applied to various perovskites for solar cells, including halide perovskites, two-dimensional Ruddlesden-Popper perovskites, and oxide perovskites. This comprehensive overview aims to inspire new ideas and strategies for optimizing solar cells.

Tetraphenylethylene (TPE) is a prototype aggregate-induced emission molecule. TPE-based conjugated macrocycles exhibit unique optical properties due to their peculiar cyclic topology. Because the symmetry of macrocycles strongly affects their photophysical properties, here we report a single-molecule study of the structures and orbitals of two TPE-based macrocycles of (C26H18)4 and (C26H18)6. Using scanning tunneling microscopy and spectroscopy, we discover that both macrocycles undergo spontaneous symmetry breaking in their conformations and frontier orbitals. The computational analyses reveal that the symmetry breaking is driven by a subtle interplay of higher extended conjugation between phenyl and node carbon atoms and conformation flexibility of the macrocycles. The observed symmetry breaking in TPE-based macrocycles is expected to strongly alter their photophysical properties.

Bismuth vanadate (BiVO4) is a promising photoanode material that has been widely employed to address environmental pollution and the energy crisis. However, defect states substantially affect the efficiency of BiVO4 photoanodes, and practical applications are severely limited because the fabrication of large-area photoanodes possessing excellent and uniform photoelectrochemical (PEC) activities remains challenging. Herein, bismuth and oxygen dual vacancy-engineered BiVO4 photoanodes were fabricated by cosputtering BiVO4 and V targets. The Bi/V atomic ratio of the BiVO4 photoanode was tailored by tuning the sputtering power of the V target (P V), thereby regulating both vacancy types in the BiVO4 photoanode. The optimized BiVO4 photoanode was fabricated at a P V of 300 W and featured the highest bismuth vacancy (Bivac) concentration (12%) and oxygen vacancy (Ovac) concentration. Under solar spectrum air mass 1.5 irradiation, the current density of the optimized BiVO4 photoanode was 1.9 mA/cm2 (at 1.6 VRHE (versus a reversible hydrogen electrode)), which was 11.9 times higher than that of the vacancy-free BiVO4 photoanode (0.16 mA/cm2). Meanwhile, the optimized dual vacancy-engineered BiVO4 photoanode exhibited the highest tetracycline hydrochloride degradation efficiency (79%) within 12 min, which was 2.9 times higher than that of the vacancy-free BiVO4 photoanode (27%). The promoted PEC activity is ascribed to the high carrier concentration and efficient Bivac- and Ovac-derived charge transport. This work offers a strategy for fabricating highly efficient, large-area BiVO4 photoanodes containing adjustable Bivac and Ovac concentrations.

Carbon nanorings (CNRs) serve as an ideal quantum system for novel electronic and magnetic properties. Although extensive theoretical studies utilizing molecular dynamics (MD) simulations have investigated the formation and structural characteristics of CNRs, systematically analyzing their properties across various toric sizes remains challenging due to the inherent complexity of this system. In this study, we introduce a novel finite element method, the Chebyshev–Ritz method, as an alternative approach to investigating the structural properties of CNRs. Previous MD simulations demonstrated that stable CNRs adopt a regular buckled shape at specific toric sizes. By meticulously selecting mechanical parameters, we observe that the critical deformation of a CNR with 50 repeated units, as determined by the Chebyshev–Ritz method, aligns with an MD simulation presenting a buckling number of 14. Additionally, the implementation of the Chebyshev–Ritz method with a constant mechanical parameter for 50 repeated units reveals a structural transition at varying toric sizes, leading to the stabilization of buckling numbers 13, 14, and 15. This structural transition across different buckling modes has also been corroborated by MD simulations. Our approach offers a reliable and accurate means of examining the structural properties of large-scale nanomaterials and paves the way for further exploration in nanoscale mechanics.

We present our studies on the adsorption, deprotonation, and reactions of 4,4″-diethynyl-1,1':4',1″-terphenyl on Cu(111) under ultrahigh-vacuum conditions using scanning tunneling microscopy combined with density functional theory calculations. Sequential annealing treatments induce deprotonation of pristine molecules followed by chemical reactions, resulting in branched nanostructures. Within the nanostructures, a previously unreported, double-spot linkage is observed. Our density functional theory calculations unravel that this linkage corresponds to a five-membered copper metallacycle.

We report the self-assembly of a monolayer metal-organic framework of Cu-benzenehexol (BHO) on a graphene/SiC substrate assisted by in situ Cu-catalyzed deprotonation reactions. The density functional theory calculations reveal that the free-standing framework is a semiconductor with a band gap of 0.485 eV. Interestingly, upon adsorption on the substrate, the Fermi level is up-shifted to the conduction band of the free-standing framework due to the n-doped graphene on SiC, while the other band structure features are largely preserved. The metallic nature corroborates the scanning tunneling microscopy images acquired near the Fermi level. This work demonstrates that the graphene substrate, which interacts weakly with the framework, can be used to tune the Fermi level of the metal-organic framework.

Due to the potential for high energy harvesting capacity, subwavelength scale semiconductor nanostructured arrays are used to address the issue of single-junction thin-film solar cells' limited solar energy harvesting. Along with numerical simulations, an effective and efficient algorithm is crucial to maximizing the optical field modulation and energy trapping capacity of nanostructures. Based on the effective medium theory and the leaky mode resonance, an analytical feedback algorithm is suggested in this study to determine the precise the dimensions of vertically aligned InP stepped nanocylinders (SNCs) for maximum solar energy absorption. For both square and hexagonally arranged two-segment or three-segment InP SNC arrays, the ideal geometrical dimensions were quantitatively estimated for maximum energy harvesting. Densities of short-circuit current Jscs under the AM 1.5G spectrum's illumination as the measurement standard, they were computed for each SNC array. The maximal Jsc of 32.85 mA/cm2 was obtained with square three-segment InP SNC arrays. The optimized SNC arrays for the maximum light absorption are also validated and examined using thorough finite-difference time-domain computational simulations. The algorithm estimated maximum Jsc had tolerances of under 1.8% for all scenarios, which, when compared to simulations, shows that this analytical method offers a practical and efficient means to direct the design of high-performance InP SNC arrays solar cells.

The emergence of quantum magnetism in nanographenes provides ample opportunities to fabricate purely organic devices for spintronics and quantum information. Although heteroatom doping is a viable way to engineer the electronic properties of nanographenes, the synthesis of doped nanographenes with collective quantum magnetism remains elusive. Here, a set of nitrogen-doped nanographenes (N-NGs) with atomic precision are fabricated on Au(111) through a combination of imidazole [2+2+2]-cyclotrimerization and cyclodehydrogenation reactions. High-resolution scanning probe microscopy measurements reveal the presence of collective quantum magnetism for nanographenes with three radicals, with spectroscopic features which cannot be captured by mean-field density functional theory calculations but can be well reproduced by Heisenberg spin model calculations. In addition, the mechanism of magnetic exchange interaction of N-NGs has been revealed and compared with their counterparts with pure hydrocarbons. Our findings demonstrate the bottom-up synthesis of atomically precise N-NGs which can be utilized to fabricate low-dimensional extended graphene nanostructures for realizing ordered quantum phases.

We demonstrate that the topological Hall effect (THE) in a $\mathrm{Pd}/{\mathrm{Tm}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ (TmIG) bilayer can be delicately manipulated by ${\mathrm{H}}_{2}$ with a maximum $100%$ tunability in the reversible manner. This phenomenon originates from the variation of the Dzyaloshinskii-Moriya interaction (DMI) at the Pd/TmIG interface, which can be effectively tuned by the absorption/desorption of ${\mathrm{H}}_{2}$ in Pd. Furthermore, we show that the THE in a Pd/W/TmIG trilayer barely changes by applying ${\mathrm{H}}_{2}$ even the W layer is only 1-nm-thick, which indicates that the DMI generated by the W/TmIG interface is responsible for the THE, and the change in the net spin accumulation at the W/TmIG interface has no effect on the THE. Finally, we show that the Cu/TmIG interface can generate sufficient interfacial DMI to induce THE, even Cu is a light metal with weak spin-orbit coupling. Our study provides a simple approach to delicately manipulate the THE in spintronic devices and paves a practical way for developing more sensitive hydrogen sensors based on the spintronic technology.

Owing to their conformational flexibility, soft molecules with side chains play a crucial role in molecular self-assembly or self-organization processes toward bottom-up building of supramolecular nanostructures. However, the influence of the rotating side chains in the confined space and subsequent surface-confined supramolecular self-assembly remains rarely explored. Herein, using the spatial confinement effect between soft building blocks, we realized size control on surface-confined supramolecular coordination self-assembly through the synergy between the repulsive steric hindrance and the attractive chemical interactions. Combining scanning tunneling microscopy with density functional theory calculations and Monte Carlo simulations, we elucidated the effective repulsive force generated by the thermal wiggling motions of the soft building blocks, allowing length tuning of the self-assembled chain structures. Through a delicate balance between the repulsive interaction induced by the spatial confinement effect and the coordinate chemical interaction, we provide a new strategy for controlling the geometry of the on-surface supramolecular nanostructures.