Journal of the American Chemical Society最新文献

This paper presents the first implementation of electrically conductive metal-organic framework (MOF) Ni₃(2,3,6,7,10,11-hexaiminotriphenylene)₂ (Ni₃(HITP)₂) integrated with nickel bis(diimine) (Ni-BDI) units for efficient solid-state electrochemical carbon dioxide (CO₂) capture. The electrochemical cell assembled using Ni₃(HITP)₂ as working electrodes can reversibly capture and release CO₂ through potential control. A high-capacity utilization of 96% and a Faraday efficiency of 98% have been achieved. The material also exhibits excellent electrochemical stability with its capacity maintained during 50 capture-release cycles and resistance to general interferences, including O₂, H₂O, NO₂, and SO₂. Capacity utilization of up to 35% is obtained at CO₂ concentrations as low as 1%. The capture of CO₂ at concentrations ranging from 1% to 100% requires exceptionally low energy consumption of only 30.5-72.4 kJ mol^-1. Studies combining spectroscopic experiments and computational approaches reveal that the CO₂ capture and release mechanism involves reversible carbamate formation on the N atom of the Ni-BDI unit in the MOF upon its one-electron redox reaction.

The assembly of molecules to form covalent networks can create varied lattice structures with physical and chemical properties distinct from those of conventional atomic lattices. Using the smallest stable [5,6]fullerene units as building blocks, various 2D C₂₄ networks can be formed with superior stability and strength compared to the recently synthesized monolayer polymeric C₆₀. Monolayer C₂₄ harnesses the properties of both carbon crystals and fullerene molecules, such as stable chemical bonds, suitable band gaps, and large surface area, facilitating photocatalytic water splitting. The electronic band gaps of C₂₄ are comparable to those of TiO₂, providing appropriate band edges with sufficient external potential for overall water splitting over the acidic and neutral pH range. Upon photoexcitation, strong solar absorption enabled by strongly bound bright excitons can generate carriers effectively, while the type-II band alignment between C₂₄ and other 2D monolayers can separate electrons and holes in individual layers simultaneously. Additionally, the number of surface-active sites of C₂₄ monolayers are three times more than that of their C₆₀ counterparts in a much wider pH range, providing spontaneous reaction pathways for the hydrogen evolution reaction. Our work provides insights into materials design using tunable building blocks of fullerene units with tailored functions for energy generation, conversion, and storage.

Polymorph selection and efficient crystallization are central goals in zeolite synthesis. Crystalline seeds are used for both purposes. While it has been proposed that zeolite seeds induce interzeolite transformation by dissolving into structural units that promote nucleation of the daughter crystal, the seed's structural elements do not always match those of the target zeolite. This discrepancy raises the question of how the seed promotes the daughter phase. Here, we present the first molecularly resolved investigation of seed-assisted zeolite synthesis. Using molecular simulations, we reproduce the experimental finding that a parent zeolite can promote the nucleation of a daughter zeolite even when it lacks common composite building units (CBUs) or crystal planes. Modeling the seed-assisted synthesis of an AFI-type zeolite using zeolite CHA, our simulations indicate that stand-alone CBUs from the parent seed do not facilitate daughter crystal formation. However, introducing the intact seed significantly reduces the synthesis time, supporting that seed integrity is key to increased efficiency. This reduction arises from the cross-nucleation of the AFI-type zeolite on the CHA (001) face. We find that parent and daughter zeolites are connected by an interfacial transition layer with an order distinct from that of both zeolites. Simulations reveal that cross-nucleation occurs over a broad range of synthesis conditions. We argue that cross-nucleation would be most favorable for zeolite pairs that share crystalline planes such as those forming intergrowths. Our findings suggest that the prevalence of intergrowths with a common lattice plane in zeolite synthesis is likely a kinetic effect of accelerated cross-nucleation.

The M₆L₄ cage, self-assembling from six Pd(II) or Pt(II) 90-degree blocks and four triazine-cored triangular ligands, has an effective hydrophobic cavity of about 450 ų capable of encapsulating one or more small molecules. Here, from the same components, we successfully constructed an M₉L₆ cage with an internal volume expanded to 1540 ų via the self-assembly of an M₈L₆ precursor using pillar[5]arene as a template. This cage retains the high molecular recognition ability of the M₆L₄ cage while recognizing medium-sized guest molecules with molecular weights of up to ∼1600.

Covalent organic frameworks (COFs) are created by the condensation of molecular building blocks and nodes to form two-dimensional (2D) or three-dimensional (3D) crystalline frameworks. The diversity of molecular building blocks with different properties and functionalities and the large number of possible framework topologies open a vast space of possible well-defined porous architectures. Besides more classical applications of porous materials such as molecular absorption, separation, and catalytic conversions, interest in the optoelectronic properties of COFs has recently increased considerably. The electronic properties of both the molecular building blocks and their linkage chemistry can be controlled to tune photon absorption and emission, to create excitons and charge carriers, and to use these charge carriers in different applications such as photocatalysis, luminescence, chemical sensing, and photovoltaics. In this Perspective, we will discuss the relationship between the structural features of COFs and their optoelectronic properties, starting with the building blocks and their chemical connectivity, layer stacking in 2D COFs, control over defects and morphology including thin film synthesis, exploring the theoretical modeling of structural, electronic, and dynamic features of COFs, and discussing recent intriguing applications with a focus on photocatalysis and photoelectrochemistry. We conclude with some remarks about present challenges and future prospects of this powerful architectural paradigm.

Electrolyte alkaline cations can significantly modulate the reaction selectivity of electrochemical CO₂ reduction (eCO₂R), enhancing the yield of the valuable multicarbon (C₂₊) chemical feedstocks. However, the mechanism underlying this cation effect on the C-C coupling remains unclear. Herein, by performing constant-potential AIMD simulations, we studied the dynamic behavior of interfacial K⁺ ions over Cu surfaces during C-C coupling and the origin of the cation effect. We showed that the specific adsorption of K⁺ readily occurs at the surface sites adjacent to the *CO intermediates on the Cu surfaces. Furthermore, this specific adsorption of K⁺ during *CO-*CO coupling is more important than quasi-specific adsorption for enhancing coupling kinetics, reducing the coupling barriers by approximately 0.20 eV. Electronic structure analysis revealed that charge redistribution occurs between the specifically adsorbed K⁺, *CO, and Cu sites, and this can account for the reduced barriers. In addition, we identified excellent *CO-*CO coupling selectivity on Cu(100) with K⁺ ions. Experimental results show that suppressing surface K⁺-specific adsorption using the surfactant cetyltrimethylammonium bromide (CTAB) significantly decreases the Faradaic efficiency for C₂ products from 41.1% to 4.3%, consistent with our computational findings. This study provides crucial insights for improving the selectivity toward C₂₊ products by rationally tuning interfacial cation adsorption during eCO₂R. Specifically, C-C coupling can be enhanced by promoting K⁺-specific adsorption, for example, by confining K⁺ within a coated layer or using pulsed negative potentials.

The ability to store and release energy efficiently is crucial for advancing sustainable energy technologies, and light-driven molecular isomerization presents a promising solution. However, a persistent challenge in this field is achieving both high stability of the energy-storing photoisomer and establishing efficient catalysis for back-isomerization, a critical process for releasing the stored energy as heat. In this work, we introduce a conceptually new molecular system designed for long-term energy storage, which is based on the reversible isomerization of ortho-methylacetophenone ⇄ benzocyclobutenol. Key to the success of this system is the strategic placement of a trifluoromethyl group, which enhances the overall performance by preventing unwanted side reactions during photochemical cyclization and by increasing the stability of the benzocyclobutenol moiety. Back isomerization is established using simple organic bases as catalysts, taking advantage of significant rate differences between normal and anionic electrocyclic ring-openings. This approach allows for controlled and predictable heat release under ambient conditions, positioning this molecular pair as a promising candidate for practical energy storage solutions.

Chiral 1,3-amino alcohols are ubiquitous structural motifs in natural products and active pharmaceutical ingredients. We present a highly enantioselective, inverse-electron-demand hetero-Diels-Alder reaction of olefins with in situ generated N-Boc-formaldimine catalyzed by strong and confined Bro̷nsted acids. This transformation provides direct access to valuable 1,3-amino alcohols from styrenes and 1,1-disubtituted alkenes. Isotope labeling studies and kinetic analysis reveal an unusual mechanism involving an oxazinium intermediate and a catalyst order greater than one.

Sm-doped Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (Sm-PMN-PT) bulk materials have revealed outstanding ferroelectric and piezoelectric properties due to enhanced local structural heterogeneity. In this study, we further explore the potential of Sm-PMN-PT by fabricating epitaxial thin films by pulsed laser deposition, revealing that Sm doping significantly improves the capacitive energy-storage, piezoelectric, electrocaloric, and pyroelectric properties of PMN-PT thin films. These Sm-PMN-PT thin films exhibit fatigue-free performance up to 10⁹ charge-discharge cycles and maintain thermal stability across a wide temperature range from -40 to 200 °C. Notably, the films demonstrate a colossal electrocaloric effect with a temperature change of 59.4 K and a remarkable pyroelectric energy density reaching 40 J cm^-3. By using scanning transmission electron microscopy and phase-field modeling, we revealed that these exceptional properties arise from the increased local structural heterogeneity and strong local electric fields along spontaneous polarization directions, facilitating the nucleation of polymorphic nanodomains characterized by a slush-like polar structure. These findings highlight the enormous potential of Sm-PMN-PT films in capacitive energy storage and solid-state electrothermal energy interconversion. Furthermore, this approach holds broad potential for other relaxor ferroelectrics by enabling the manipulation of nanodomain structures, paving the way for developing robust multifunctional materials.