Journal of the American Chemical Society最新文献

Here, we report the synthesis of a family of chiral Zn^II₄L₄ tetrahedral cages by subcomponent self-assembly. These cages contain a flexible trialdehyde subcomponent that allows them to adopt stereochemically distinct configurations. The incorporation of enantiopure 1-phenylethylamine produced Δ₄ and Λ₄ enantiopure cages, in contrast to the racemates that resulted from the incorporation of achiral 4-methoxyaniline. The stereochemistry of these Zn^II₄L₄ tetrahedra was characterized by X-ray crystallography and chiroptical spectroscopy. Upon binding the enantiopure natural product podocarpic acid, the Zn^II stereocenters of the enantiopure Δ₄-Zn^II₄L₄ cage retained their Δ handedness. In contrast, the metal stereocenters of the enantiomeric Λ₄-Zn^II₄L₄ cage underwent inversion to a Δ configuration upon encapsulation of the same guest. Insights gained about the stereochemical communication between host and guest enabled the design of a process for acid/base-responsive guest uptake and release, which could be followed by chiroptical spectroscopy.

Colloidal nanocrystals (NCs) are active materials in different applications, wherein their shape dictates their properties, such as optical or catalytic properties, and, thus, their performance. Hence, learning to tune the NC shape is an important goal in chemistry, with implications in other fields of research. A knowledge gap exists in the chemistry of non-noble metals, wherein design rules for shape control of NCs are still poorly defined compared to those of other classes of materials. Herein, we demonstrate that tuning the precursor reactivity is crucial to obtaining a continuous shape modulation from single-crystalline to twinned and stacking fault-lined Cu NCs. This tunability is unprecedented for non-noble metal NCs. We achieve this result by using diphenylphosphine in place of the most commonly used trioctylphosphine. Using in situ X-ray absorption spectroscopy, we show that the temperature modifies the reaction kinetics of an in situ-forming copper(I)bromide-diphenylphosphine complex during the synthesis of Cu NCs. We propose the presence of a P-H functionality in the phosphine to explain the higher reactivity of this precursor complex formed with diphenylphosphine compared to that formed with trioctylphosphine. This work inspires future studies on the role of phosphine ligands during the synthesis of Cu NCs to rationally target new morphologies, such as high-index faceted Cu NCs, and can be conceptually translated to other transition-metal NCs.

Cysteine reactive groups are a mainstay in the design of covalent drugs and probe molecules, yet only a handful of electrophiles are routinely used to target this amino acid. Here, we report the development of scalable thiol reactivity (STRP), a method which enables the facile interrogation of large chemical libraries for intrinsic reactivity with cysteine. High throughput screening using STRP identified the azetidinyl oxadiazole as a moiety that selectively reacts with cysteine through a ring opening-based mechanism, capable of covalently engaging cysteine residues broadly across the human proteome. We show the utility of this reactive group with the discovery of an azetidinyl oxadiazole containing a small molecule that augments the catalytic activity of the deubiquitinase UCHL1 in vitro and in cells by covalently modifying a cysteine distal to its enzymatic active site. This study adds a novel cysteine targeting group to the electrophilic lexicon and provides robust methodology to rapidly surveil libraries for reactivity with cysteine.

On-purpose atomic scale design of catalytic sites, specifically active and selective at low temperature for a target reaction, is a key challenge. Here, we report teamed Pd₁ and Mo₁ single-atom sites that exhibit high activity and selectivity for anisole hydrodeoxygenation to benzene at low temperatures, 100-150 °C, where a Pd metal nanoparticle catalyst or a MoO₃ nanoparticle catalyst is individually inactive. The catalysts built from Pd₁ or Mo₁ single-atom sites alone are much less effective, although the catalyst with Pd₁ sites shows some activity but low selectivity. Similarly, less dispersed nanoparticle catalysts are much less effective. Computational studies show that the Pd₁ and Mo₁ single-atom sites activate H₂ and anisole, respectively, and their combination triggers the hydrodeoxygenation of anisole in this low-temperature range. The Co₃O₄ support is inactive for anisole hydrodeoxygenation by itself but participates in the chemistry by transferring H atoms from Pd₁ to the Mo₁ site. This finding opens an avenue for designing catalysts active for a target reaction channel such as conversion of biomass derivatives at a low temperature where neither metal nor oxide nanoparticles are.

The formation of a homogeneous passivation layer based on phase-pure two-dimensional (2D) perovskites is a challenge for perovskite solar cells, especially when upscaling the devices to modules. Here we reveal a chain-length-dependent and halide-related phase separation problem of 2D perovskite growing on top of three-dimensional perovskites. We demonstrate that a homogeneous 2D perovskite passivation layer can be formed upon treatment of the perovskite layer with formamidinium bromide in long-chain ( >10) alkylamine ligand salts. We achieve champion active-area efficiencies of 25.61%, 24.62% and 23.60% for antisolvent-free processed small- (0.14 cm²) and large-size (1.04 cm²) devices and mini-modules (13.44 cm²), respectively. This passivation strategy is compatible with printing technology, enabling champion aperture-area efficiencies of 18.90% and 17.59% for fully slot-die printed large solar modules with areas of 310 cm² and 802 cm², respectively, demonstrating the feasibility of the upscaling manufacturing.

Small modular reactors (SMRs) offer a unique solution to the challenge of decarbonizing mid- and high-temperature industrial processes. Here we develop deployment pathways for four SMR designs displacing natural gas in industrial heat processes at 925 facilities across the United States under diverse policy and factory or onsite learning conditions. We find that widespread SMR deployment in industry requires gas prices above US$6 per metric million British thermal unit, low capital cost over-runs and/or aggressive carbon taxes. At gas prices of US$6–10 per metric million British thermal unit, 7–55 gigawatt-thermal (GW_t) of SMRs could be economically deployed by 2050, reducing annual emissions by up to 59 Mt of CO₂-equivalent. Of this deployment, 2–24 GW_t rely on module manufacturing learning within a factory. Widespread deployment potential hinges on avoiding substantial cost escalation for early investments. Policy levers such as direct subsidies are not effective at incentivizing sustainable deployment, but aggressive carbon taxes and investment tax credits provide effective support for SMR success.

Microscopy provides a proxy for assessing the operation of perovskite solar cells, yet most works in the literature have focused on bare perovskite thin films, missing charge transport and recombination losses present in full devices. Here we demonstrate a multimodal operando microscopy toolkit to measure and spatially correlate nanoscale charge transport losses, recombination losses and chemical composition. By applying this toolkit to the same scan areas of state-of-the-art, alloyed perovskite cells before and after extended operation, we show that devices with the highest macroscopic performance have the lowest initial performance spatial heterogeneity—a crucial link that is missed in conventional microscopy. We show that engineering stable interfaces is critical to achieving robust devices. Once the interfaces are stabilized, we show that compositional engineering to homogenize charge extraction and to minimize variations in local power conversion efficiency is critical to improve performance and stability. We find that in our device space, perovskites can tolerate spatial disorder in chemistry, but not charge extraction.