Journal of the American Chemical Society最新文献

Per- and polyfluoroalkyl substances (PFAS) are of increasing concern due to their environmental persistence and adverse effects on health. The recovery of fluoride from the decomposition of concentrated sources of PFAS (e.g., refrigerants, protective coatings, and foams) enables a circular economy. Recent efforts have largely focused on one-pot, transfer fluorination strategies, with limited examples of forming isolable fluoride reagents, which represent the broadest opportunities for valorization. Here, we establish a direct electrochemical strategy to recycle nonpolymeric PFAS into a range of synthetically important fluoride reagents. The choice of electrolyte and solvent is critical in controlling whether fluoride or bifluoride ions are generated, enabling selective access to distinct reagents. These findings establish electrochemistry as a powerful and versatile platform for transforming environmentally persistent PFAS waste into valuable chemical resources.

Catalytic ammonia decomposition for hydrogen release at reduced temperatures is a critical component of the hydrogen energy roadmap. However, conventional nonprecious transition metal (TM) catalysts, such as Ni and Co, typically suffer from a high energy barrier in the N-N coupling step. In this study, we report that a stable Zintl phase silicide of BaSi₂ functions as an efficient support for Ni and Co catalysts in ammonia decomposition via the formation of TM-nitrogen-barium intermediates at the TM-BaSi₂ interface. Characterizations using kinetic studies, X-ray photoelectron spectroscopy (XPS), and density functional theory calculations suggest that electron transfer occurs from the interfacial low-valence barium to nitrogen atoms bonded to TM at the TM-BaSi₂ interface, which leads to the formation of TM-nitrogen-barium intermediates and in turn lowers the energy barrier for the rate-determining N-N coupling step. This promotion enables Ni- or Co-loaded BaSi₂ catalysts to significantly outperform conventional nonprecious metal catalysts and become comparable to the Ru-based catalysts. These results offer a new perspective for the future design of nonprecious metal catalysts for ammonia decomposition at reduced temperature.

Despite the widespread significance of the Fe(III)-catalyzed oxidation of S(IV) for sulfur chemistry and atmospheric aerosols, its reaction mechanism and accelerated kinetics at the microdroplet surface remain poorly understood. Herein, integrating Born-Oppenheimer molecular dynamic (BOMD) simulations and electron paramagnetic resonance spectrometer (EPR) experiment, the results reveal that the rate-determining SO₃^·- radical generation exhibits orders of magnitude enhancement at the air-water interface compared to that established in solution-phase kinetics. This interfacial acceleration is progressively amplified under more acidic conditions, as corroborated by both lower calculated free energy changes and enhanced experimentally measured SO₃^·- signal intensities with decreasing pH. Challenging the traditional Fe(III) solubility-driven paradigm, we demonstrate that the elevated rate mainly stems from highly reactive Fe(III) speciation under low pH conditions, whose reduced molecular orbital energy level improves electron-accepting capacity and thereby accelerates the oxidation reaction as acidity increases. Critically, our simulations establish an unprecedented concerted proton-electron transfer (CPET) mechanism, supported by synchronous proton and electron transfer across all dynamic events. This work elucidates the origin of the high efficiency of Fe(III)-catalyzed S(IV) oxidation in microdroplets and provides fundamental insights into pH-dependent transition-metal ion speciation as a previously under-appreciated factor impacting atmospheric sulfate aerosol formation and sulfur cycling.

A comprehensive understanding of RNA biology requires methods to visualize transcripts and their interactions within physiological environments. However, few technologies can report on multiple RNAs continuously and in living systems. We are addressing this void with bioluminescent probes. Bioluminescence does not require excitation light and can enable sensitive, noninvasive readouts in a variety of settings. Here, we report a panel of structured RNA tags and luciferase fragments (RNA lanterns) for multiplexed RNA detection. The lanterns emit few photons on their own but assemble and emit light when brought into proximity by the RNA tags. Three orthogonal tag-lantern combinations were designed based on known RNA-binding proteins that recognize distinct targets. The probes were optimized in vitro for selective transcript detection. We further applied the tags and lanterns in cultured cells, achieving multitarget imaging with good subcellular resolution. Collectively, the probes expand the toolkit for RNA imaging and will facilitate efforts to trace RNA targets in living systems.

Herein, we report a simple, one-pot, scalable process for the preparation of a series of enamides, which were subsequently hydrogenated with high efficiency and excellent enantioselectivity to the corresponding chiral amides using the Rh-ZhangPhos catalyst. This methodology is practical and facilitates easy postreaction handling, with the hydrogenation providing nearly perfect stereoselectivity. DFT studies uncovered distinct rate-determining steps for competing enantiomeric pathways: migrational insertion for the major product and reductive elimination for the minor product, challenging conventional assumptions of a unified mechanistic origin. Noncovalent interaction analysis, particularly steric repulsion in the reductive elimination step, offers a theoretical rationale for long-standing empirical strategies in bisphosphine ligand design, bridging experiment, and computation in asymmetric hydrogenation.