Tao Lin

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 (Ni^H) and low-spin (Ni^L) Ni centers alternately embedded in the coordination chains on Au(111) at the atomic scale, revealing preferred O₂ adsorption at Ni^H. Density functional theory studies demonstrate that this selectivity arises from the distinct d-electron configurations of Ni^H and Ni^L, which significantly affect the O₂-Ni hybridization. The stronger O₂ adsorption at Ni^H than at Ni^L drives a spin transition of Ni^L upon O₂ adsorption, which could be kinetically unfavorable and thus further contribute to the observed selective O₂-Ni^H binding. These findings offer microscopic insights into the spin-modulated O₂ adsorption.

The schematic summary of electrolyte design strategies, properties, and advantages of chlorinated electrolytes for LMBs.

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.

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.

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.

This article presents recent research progress of scanning tunneling microscopy/spectroscopy applied to perovskite materials for solar cells, providing valuable insights into their fundamental properties at the atomic scale.

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.

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 J _sc s under the AM 1.5G spectrum's illumination as the measurement standard, they were computed for each SNC array. The maximal J _sc of 32.85 mA/cm ² 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 J _sc 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.