Enantioselective photocatalytic synthesis of bicyclo[2.1.1]hexanes as ortho-disubstituted benzene bioisosteres with improved biological activity
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Hydrogen-bonded organic frameworks for photocatalytic synthesis of hydrogen peroxide
Photocatalysis provides a sustainable and environment-friendly strategy to produce H2O2, yet the catalytic efficiency of H2O2 overall photosynthesis (O2 + 2H2O → 2H2O2) needs to be further improved, especially in the absence of additional cocatalysts, photosensitizers and sacrificial agents. Here we find that hydrogen-bonded organic frameworks can serve as photocatalysts for H2O2 overall photosynthesis under the above-mentioned conditions. Specifically, we constructed a donor–acceptor hydrogen-bonded organic framework that exhibits a high photocatalytic activity for H2O2 overall photosynthesis, with a production rate of 681.2 μmol g-1 h-1. The control experiments and theoretical calculation revealed that the hydrogen-bonded organic frameworks with donor–acceptor structures can not only accelerate the charge separation and transfer but also optimize the reaction pathways, which significantly boosts the photocatalytic efficiency in H2O2 overall photosynthesis. This work provides insights into the design and development of efficient photocatalysts for overall H2O2 photosynthesis.
Enantioselective C–H annulations enabled by either nickel- or cobalt-electrocatalysed C–H activation for catalyst-controlled chemodivergence
Enantioselective electrocatalysis shows unique potential for the sustainable assembly of enantiomerically enriched molecules. This approach allows electro-oxidative C–H activation to be performed paired to the hydrogen evolution reaction. Recent progress has featured scarce transition metals with limited availability. Here we reveal that the earth-abundant 3d transition metals nickel and cobalt exhibit distinctive performance for enantioselective electrocatalysis with chemodivergent reactivity patterns. Enantioselective desymmetrizations of strained bicyclic alkenes were achieved through C–H annulations. A data-driven optimization of chiral N,O-bidentate salicyloxazoline-type ligands was crucial for enhancing enantioselectivity in nickel electrocatalysis. Notably, in the transition state of the enantio-determining step, secondary weak attractive π–π and CH–π interactions were identified, reflecting the informed adaptations in the ligand design. Detailed mechanistic investigations by experimental and computational studies revealed for the nickel electrocatalysis a C–N bond-forming reductive elimination from nickel(III) and for the cobalt electrocatalysis a C–C bond-forming nucleophilic addition from cobalt(III) as the product-determining steps.
Enantioselective synthesis of chiroplasmonic helicoidal nanoparticles by nanoconfinement in chiral dielectric shells
Helicoid metal nanoparticles with intrinsic chirality have unveiled tailorable properties and unlocked many chirality-related applications across various fields. Nevertheless, the existing strategies for enantioselective synthesis of helicoid metal nanoparticles have been predominantly limited to gold. Here, we demonstrate a robust and versatile strategy for the enantioselective synthesis of helicoid nanoparticles beyond gold, leveraging chiral nanoconfinement provided by chiral SiO2 or nanoshells. The chiral nanoconfinement strategy enables the decoupling of ligand-directed crystal growth from chiral induction, allowing for the independent tuning of these two critical aspects. As a result, this approach can not only facilitate the replication of chiral shapes from the chiral nanoshells but also allow the generation of alternative chiral shapes. By employing this approach, we demonstrate the enantioselective synthesis of helicoid Pt, Au@Pt, Au@Pd, Au@Ag, and Au@Cu nanoparticles. The chiroplasmonic properties of Pt- and Pd-based chiral nanoparticles have been discovered, and the inversion of chiroplasmonic properties of Ag-based chiral nanoparticles via facet control has been documented and theoretically explained. The chiral nanoconfinement strategy enriches the toolbox for creating chiral nanoparticles and supports their exploration in diverse applications.
Redox-active inverse crowns for small molecule activation
Cyclic crown ethers bind metal cations to form host–guest complexes. Lesser-known inverse crowns are rings of metal cations that encapsulate anionic entities, enabling multiple deprotonation reactions, often with unusual selectivity. Self-assembly of a cycle of metal cations around the multiply charged carbanion during the deprotonation reaction is the driving force for this reactivity. Here we report the synthesis of a pre-assembled inverse crown featuring Na+ cations and a redox-active Mg0 centre. Reduction of N2O followed by N2 release and subsequent encapsulation of O2− demonstrates its reduce-and-capture functionality. Calculations reveal that this essentially barrier-free process involves a rare N2O2− dianion, embedded in the metalla-cycle. The inverse crown can adapt itself for binding larger anions like N2O22− through a self-reorganization process involving ring expansion. The redox-active inverse crown combines the advantages of a strong reducing agent with anion stabilizing properties provided by the ring of metal cations, leading to high reactivity and selectivity.
Photo-assisted technologies for environmental remediation
Industrial processes can lead to air and water pollution, particularly from organic contaminants such as toluene and antibiotics, posing threats to human health. Photo-assisted chemical oxidation technologies leverage light energy to mineralize these contaminants. In this Review, we discuss the mechanisms and efficiencies of photo-assisted advanced oxidation processes for wastewater treatment and photothermal technologies for air purification. The integration of solar energy enhances degradation efficiency and reduces energy consumption, enabling more efficient remediation methods. We evaluate the technological aspects of photo-assisted technologies, such as photo-Fenton, photo-persulfate activation, photo-ozonation and photoelectrochemical oxidation, emphasizing their potential for practical applications. Finally, we discuss the challenges in scaling up photo-assisted technologies for specific environmental remediation needs. Photo-assisted technologies have demonstrated effectiveness in environmental remediation, although large-scale applications remain constrained by high costs. Future potential applications of photo-assisted technologies will require that technology selection be tailored to specific pollution scenarios and engineering processes optimized to minimize costs.
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