Angewandte Chemie International Edition最新文献

This study introduces a novel approach to inverse vulcanization by utilizing a commercially available triaziridine crosslinker as an alternative to conventional olefin-based crosslinkers. The model reactions reveal a self-catalyzed ring-opening of "unactivated" aziridine with elemental sulfur, forming oligosulfide-functionalized diamines. The triaziridine-derived polysulfides exhibit impressive mechanical properties, achieving a maximum stress of ~8.3 MPa and an elongation at break of ~107%. The incorporation of silicon dioxide (20 wt%) enhances the composite's rigidity, yielding a Young's modulus of ~0.94 GPa. Furthermore, these polysulfides display excellent adhesion strength on various substrates, such as aluminum (~7.0 MPa), walnut (~9.6 MPa), and steel (~11.0 MPa), with substantial retention of adhesion strength (~3.3 MPa on steel) at -196 °C. The straightforward synthetic process, combined with the accessibility of the triaziridine crosslinker, emphasizes the potential for further innovations in sulfur polymer chemistry.

The photocatalytic co-reduction of CO2 and N2 is a sustainable method for urea synthesis under mild conditions. However, high-yield synthesis of urea is a challenge due to the sluggish kinetics of the C-N coupling reaction. Herein, we have successfully engineered a Z-scheme photocatalyst, SrTiO3-FeS-CoWO4, for boosting photocatalytic urea synthesis via enhancing the initial CO2 and N2 adsorption step and reducing the energy barrier for the C-N coupling reaction. A high urea yield of 8054.2 μg·gcat-1·h-1 was achieved on SrTiO3-FeS-CoWO4, which was significantly higher than the state-of-the-art. The SrTiO3-FeS-CoWO4 Z-scheme photocatalyst, with accelerated charge transfer by FeS, not only had dual active sites for the chemical adsorption and activation of CO2 and N2, but also retained the high conduction band (-1.50 eV) and accelerated supply of electrons and protons, which are responsible for its good photoreduction activity and significantly reduced energy barrier for the rate-determining step of C-N coupling reaction.

Matrix immobilization has been proven to be a favored method for enhancing the phosphorescence of carbon dots (CDs), however, it remains a significant challenge to realize time-dependent phosphorescence colors (TDPC) by embedding CDs with single emission center. In this study, we present a novel matrix-controlling strategy to regulate the microenvironment of CDs by doping limited Mn2+ in zeolite. The surrounding environment influences the surface state of the CDs, leading to the formation of different excitons. At low temperatures, Mn-coordinated CDs (C-CDs) show fast-decaying green phosphorescence, while non-coordinated CDs (NC-CDs) exhibit inherent slow-decaying blue phosphorescence. Notably, the energy transfer occurs between NC-CDs and Mn2+ to produce an ultrafast-decaying red phosphorescence, with the intensity of the red component increasing as the temperature rises. The interplay of these luminescent centers with distinct decay rates activates fascinating multi-mode TDPC behavior as the temperature changes, resulting in dynamic afterglow evolutions from red to green at 298 K, orange to green at 273 K, and green to cyan to blue at 77 K. Leveraging the diverse luminescence of CDs@MnAPO-5, a multi-dimensional dynamic afterglow color pattern was developed for advanced anti-counterfeiting applications.

Photodynamic therapy (PDT), a minimally invasive and effective local treatment, heavily depends on photosensitizer (PS) performance and oxygen availability. Despite the use of PS-based metal-organic frameworks (MOFs) to address the solubility and aggregation issues of PSs, the inherent hypoxic intolerance of mainstream Type II PDT remains challenging. Herein, we report an electron transfer strategy for the fabrication of hypoxia-tolerant Type I MOFs by encapsulating thymoquinone (TQ) into existing Type II MOFs. With TQ serving as an effective electron transfer mediator, it facilitates the electron transfer process from the MOF ligand PS to oxygen, establishing the Type I pathway and attenuating the original Type II pathway. Four representative porphyrin-based MOFs are synthesized to demonstrate the proposed strategy. Our findings reveal that TQ@MOF-1 nanoparticles (NPs) exhibit enhanced anticancer activity under hypoxic conditions and superior in vivo antitumor efficacy compared to parent MOF-1 NPs. This work offers an effective and universal strategy to modulate ROS generation in PS-based MOFs, endowing hypoxic tolerance with improved PDT performance against solid tumors.

Nitridophosphates have emerged as promising host compounds in the field of solid-state lighting. Their industrial relevance has increased significantly, mainly due to recent advances in synthetic approaches under medium-pressure (MP) conditions, including ammonothermal synthesis and hot isostatic pressing (HIP). In this study, we report on the synthesis and characterization of the quaternary representatives CaxLi10-2xP4N10 (x = 2, 2.7, 4) and Sr3Li4P4N10, prepared via a simplified ion exchange reaction under MP conditions, starting from the nitridophosphate-based lithium ion conductor Li10P4N10. The synthesis route allowed for the preservation of the anionic [P4N10]10- structural motif of the starting material, while simultaneously introducing potential doping sites for Eu2+ by incorporating divalent alkaline earth cations (Ca2+/Sr2+). Upon excitation of Eu2+ doped samples with blue light, strong luminescence due to parity-allowed 4f6(7F)5d1→4f7(8S7/2) transition can be observed in the red (Ca2Li6P4N10:Eu2+: λmax = 626 nm), yellow/orange (Ca2.7Li4.6P4N10:Eu2+: λmax1 = 506 nm, λmax2 = 592 nm and Sr3Li4P4N10:Eu2+: λmax = 596 nm) and green (Ca4Li2P4N10:Eu2+: λmax = 546 nm) spectral regions of the visible light. The compounds presented, together with the simplified synthetic approach, demonstrate the significant potential of ion exchange on Li ion conductors for the development of novel nitridophosphates in the future.

The transfer-free character of graphene growth on Silicon Carbide (SiC) makes it compatible with state-of-the-art Si semi-conductor technologies for directly fabricating high-end electronics. Although significant progress has been achieved in epitaxial growth of graphene on SiC recently, the underlying nucleation mechanism remains elusive. Here, we present a theoretical study to elucidate graphene near-equilibrium nucleation on Si-terminated hexagonal-SiC(0001) surface. It is found that the ultra-large lattice mismatch between SiC(0001) surface and graphene and the highly localized electron distribution on SiC(0001) surface lead to a distinctive nucleation process: (i) Most of the magic carbon clusters on SiC(0001) show only C1 symmetry and are mainly composed of pentagonal rings; (ii) Two possible nucleation pathways are revealed, i.e, longitudinal and circular modes; (iii) Carbon clusters are more stable on flat terraces than near atomic step edges. Based on above findings, a graphene nucleation diagram on SiC(0001) is established and experimentally observed contradictories for graphene growth on SiC(0001) are answered. Our in-depth understanding on graphene nucleation on SiC(0001) extends nucleation mechanisms of 2D crystals and will benefit high-quality graphene growth on SiC(0001).

Transition metal π-arene complexes enable the dearomatization of benzene rings to access diversified unsaturated carbocycles through multistep synthetic procedures involving sequential addition of nucleophiles and electrophiles. This work details a single-step dearomatization process by reaction of Ru(η6-arene) complexes with enolates derived from α-halo or α-(tosyloxy)esters to directly transform π-coordinated arenes to ring-expanded cycloheptatrienes.

Methanolation of olefins is introduced as a new low-pressure synthetic pathway to C1 elongated alcohols. Formally, H3COH is added to the C=C bond in a 100% atom efficient manner. Mechanistically, the overall transformation occurs as a tandem reaction sequence by combining the dehydrogenation of methanol to syngas at a CO:H2 ratio of 1:2 with subsequent hydroformylation to the corresponding aldehyde and its final hydrogenation to the alcohol. The dehydrogenation and hydrogenation steps are catalysed by a Mn/pincer complex, while the hydroformylation is accomplished by a Rh/phosphine catalyst. Using 1-octene as prototypical substrate, a yield of 80% nonanol was achieved with a ratio of 93:7 of linear to branched alcohols and turnover numbers (TONRh) of more than 17 000 could be obtained in relation to the precious metal Rhodium. The integrated catalytic system provides direct access to alcohols from olefins and "green" methanol, avoiding the handling of pressurized CO and H2 and the use of specialized high-pressure equipment as the process conditions do not exceed 10 bar with partial pressures of syngas in the range of only 1-2 bar.