Materials Horizons最新文献

The pyrolysis of metal-organic frameworks (MOFs) provides a promising route to synthesize efficient metal-N-C electrocatalysts. While most studies emphasize the metal component, here we focus on how precursor crystal size dictates the pyrolysis pathway and carbon matrix formation mechanism in Co-triazolate MOFs. By precisely controlling precursor size, we uncover two distinct transformation routes: small crystals decompose earlier, releasing acetylene that is catalytically converted by newly formed Co nanoparticles into 1D carbon nanofibers. Due to the higher decomposition temperature of large precursor crystals, this fiber-growth pathway was suppressed, leading to 3D carbon frameworks with Co nanoparticles uniformly encapsulated by graphitic layers. This size-dependent decomposition and ligand-metal interaction establishes a direct link between the precursor size, pyrolysis pathway, and final product. Benefiting from uniform encapsulation, enriched graphitic-N, and abundant Co-N sites, the 3D carbon-supported Co-N-C catalyst exhibits markedly higher hydrogen evolution reaction (HER) performance compared to its 1D counterpart. These findings highlight a pyrolysis-guided strategy for tailoring MOF-derived carbon architectures by shifting focus from metal-ligand coordination to metal-ligand interactions, offering new mechanistic insights and pathways for rational electrocatalyst design.

While macroporous carbon materials have attracted considerable attention due to their tunable porosity, chemical and thermal stability, and electrical conductivity, they still face critical limitations in achieving a balance of ultralow density, high mechanical toughness, and efficient fluid transport through a cost-effective and environmentally friendly approach. To address these issues, an ice-templating approach is employed to fabricate ultralight yet mechanically robust carbon monoliths with aligned microchannels. By unidirectionally freezing a precursor suspension containing cellulose nanofibers and a carbon source, followed by freeze-drying and pyrolysis at 900 °C, we obtain honeycomb-like structured carbon monoliths with an ultralow density (∼0.09 g cm^-3), a high compressive strength (∼3400 kPa), and well-penetrated microchannels for efficient mass transport with minimal pressure drop. The potential of these materials is demonstrated in two key applications: high-flux water purification, achieving >99% removal of rhodamine B at an exceptional flux of 20 000 L m^-2 h^-1 with excellent reusability, and rapid heat exchange of flowing water, exhibiting a heat exchange efficiency four times greater than that of commercial counterparts. This study offers a versatile strategy for designing ultralight, mechanically robust, and highly permeable macroporous carbon materials with promising applications in environmental and energy-related technologies.

Developing artificial reactors for the synthesis of peroxy (O-O) bonds offers a new route to the creation of flexible intermediate platforms. Herein, we report a selective spontaneous reaction of flavonoid with γ-cyclodextrin (γ-CD) in cyclodextrin metal-organic framework (CD-MOF-1). Remarkably, simple incubation of flavonoids within CD-MOF-1 at ambient conditions in the dark leads to the spontaneous formation of an O-O bond between flavonoid and γ-CD. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and nuclear magnetic resonance (NMR) results confirm that the isolated flavonoid-γ-CD compounds involve O-O bonds and preferentially form at the hydroxyl in the flavonol C ring (e.g., quercetin) or at the meta-phenol hydroxyl on the flavone B ring (e.g., epigallocatechin gallate, EGCG). Intriguingly, flavonoids bearing both meta- and para-hydroxyl groups in the B ring (e.g., EGCG) or those with an adjacent carbonyl on the C ring (e.g., quercetin) underwent this reaction, whereas flavonoids lacking these features (e.g., taxifolin, luteoline, apigenin, naringenin, hesperetin and daidzein) cannot trigger this reaction. Density functional theory (DFT) calculations indicate that potassium (K⁺) cations in the CD-MOF-1 reduce the bond dissociation energies (BDEs) of the relevant hydroxyl groups, catalyzing O-O bond formation. This work reveals that CD-MOF-1 can orchestrate the precise arrangement of reactants and activate their specific sites, enabling selective O-O bond formation under mild and dark conditions. We expect this discovery to encourage further development of CD-MOF-1-based platforms for mild, selective oxidative transformations and the generation of novel intermediates.

Single-walled carbon nanotubes (SWCNTs) with tailored functionalization serve as optically responsive nanoparticles, but when encapsulated by chirality-selective polymers, they often remain inert to analytes. To expand their utility, we developed a post-functionalization modification (PFM) strategy introducing oxygen defects into chirality-pure (6,5) and (7,5) SWCNTs suspended by PFO-BPy6,6' and PFO-FH, respectively. UV exposure in the presence of sodium hypochlorite (NaClO) partially displaces the polymer corona, confirmed by low-temperature fluorescence, Raman spectroscopy, dynamic light scattering, and transmission electron microscopy. To probe corona displacement, riboflavin (RB) was employed as a fluorescent reporter for the exposed SWCNT surface. Minimal RB quenching was observed with (6,5) and (7,5) SWCNTs treated with low NaClO concentration (0.01%), indicating high coverage, while dispersions treated with higher NaClO concentration (0.055%) showed strong RB quenching, reflecting reduced coverage. This trend establishes NaClO concentration as a handle to tune corona coverage. We further show that surface coverage modulates size-selective adsorption of polyaromatic hydrocarbons (PAHs). At intermediate NaClO treatment (0.02%), PFM-SWCNTs responded selectively to naphthalene (2-ring PAH), while higher treatment (0.055%) enabled response to naphthalene, fluorene, and pyrene (2, 3, and 4-ring PAH). These findings demonstrate that PFM enables controllable surface coverage and size-selective PAH interactions, broadening SWCNTs utility as optical nanoprobes.

To break through the performance bottlenecks of electromagnetic protection materials in terms of lightweight design, broadband absorption, and multifunctional integration, this work proposes a synergistic design strategy based on magneto-dielectric coupled absorbing units and periodic micro-circular array superstructures. At the microscopic scale, oleic acid (OA)-modified γ-Fe₂O₃/graphene oxide (OA-γ-Fe₂O₃/GO) composite absorbing units were constructed and organized into precisely controllable millimeter-scale periodic micro-circular arrays. Acting as an artificial electromagnetic structure capable of actively modulating the electromagnetic field distribution, the array enables multiple scattering, progressive attenuation, and continuous impedance transition within the interface, thereby significantly optimizing the energy dissipation pathways. A pressing process was employed to integrate polytetrafluoroethylene (PTFE) onto the fabric surface, realizing a high-performance composite fabric with an overall thickness of only 0.128 mm. The resulting composite exhibits outstanding performance, with a shielding effectiveness (SE_T) of 73.99 dB, a minimum reflection loss (RL_min) of -31.56 dB, and an effective absorption bandwidth (RL < -10 dB) spanning 10.93-11.83 GHz. Meanwhile, it demonstrates excellent multifunctional properties, including a water contact angle of 125.7°, a tensile strength of 142 MPa, and the retention of 93% of its initial shielding performance after 10 000 bending cycles. Compared with commercial thin shielding textiles, the proposed material achieves an improvement of over 20% in shielding effectiveness and over 30% in absorption performance. This study not only provides a high-performance electromagnetic protection material but also establishes a cross-scale "unit-structure" synergistic design framework, offering a new fundamental paradigm for developing intelligent and adaptive electromagnetic protection systems. The strategy holds great potential for applications in stealth technology, aerospace engineering, and wearable electronics.

Formaldehyde (HCHO) is a major indoor air pollutant that poses serious risks to human health, making its efficient removal a critical environmental concern. Catalytic oxidation at room and sub-ambient temperatures has attracted significant attention due to its potential to completely decompose HCHO into harmless CO₂ and H₂O. However, practical implementation remains challenging because of low reaction activation energy and limited catalyst performance at reduced temperatures. In this study, Au-loaded manganese oxide nanowire catalysts (x% Au/MnO₂-NWs) were synthesized using a colloidal deposition strategy to achieve efficient HCHO removal under ambient and sub-ambient conditions. The optimized 1% Au/MnO₂-NWs catalyst achieved complete conversion of 280 ppm HCHO at 30 °C and, remarkably, fully oxidized 20 ppm HCHO even at 0 °C, demonstrating outstanding low-temperature activity and practical potential. Comprehensive characterization studies including H₂-TPR, EPR, Raman spectroscopy, and in situ DRIFTS revealed that Au nanoparticles induced abundant oxygen vacancies, which acted as active sites for HCHO adsorption and promoted O₂ activation. The synergistic interaction between Au and MnO₂ significantly enhanced low-temperature catalytic performance, providing mechanistic insights and a solid foundation for the rational design of highly efficient catalysts for indoor formaldehyde removal.

Interfacial solar evaporation offers a sustainable route for seawater desalination, addressing global freshwater scarcity by harnessing solar energy for efficient water evaporation. However, its performance is typically constrained by the availability and intensity of sunlight. Here, we report a novel evaporator design that overcomes this limitation by extracting substantial thermal energy from the bulk water to sustain high evaporation rates even in the absence of solar input. Through rational structural design and optimization of thermal conductivity of the evaporator support, the obtained evaporators harvest energy from the bulk water far exceeding the incident solar flux, enabling rapid evaporation under diverse weather conditions. The optimized evaporator achieves an exceptional evaporation rate of 11.15 kg m^-2 h^-1 under 1.0 sun. This design strategy expands the operational window of interfacial solar evaporation and offers a robust pathway toward continuous, high-efficiency desalination in real-world environments.

Inspired by nature's reliance on antagonistic interactions to orchestrate complex dynamics, synthetic systems often replicate this by integrating multiple competing components-a strategy frequently hampered by synthetic complexity and kinetic mismatch. Here, we report a single-component spiropyran-functionalized polymer system that exhibits programmable reentrant phase transitions mediated by light-heat antagonism in reversible spiropyran isomerization. Within this system, light and heat competitively drive the interconversion of spiropyran between its ring-closed SP^- and ring-opened MCH forms, allowing precise modulation of intermolecular electrostatic interactions and thereby enabling real-time control over polymer conformation and phase transitions. Following this principle, we demonstrate versatile reversible switching of a single polymer system among nonthermoresponsive, monothermoresponsive (UCST-type), and reentrant thermoresponsive states-the latter displaying LCST behavior at low temperatures and UCST behavior at high temperatures. This light-heat regulatory mechanism is further extended to hydrogels, where it enables programmable reentrant volumetric transitions and autonomous oscillatory deformation. By employing noninvasive light to flexibly tailor multimode responsiveness in a single system, our work establishes a robust and generalizable platform for dynamically programmable matter with prospects in soft robotics and biomedicine.

Pathological macrophage activation orchestrates atherosclerotic plaque progression through sustained inflammation, necrotic core expansion, and plaque destabilization, a process recalcitrant to current targeted therapies. We address this fundamental challenge by engineering a living macrophage-based theranostic cyborg (MφMB-Au) that integrates precision plaque homing with spatiotemporally controlled immunomodulation. This platform exploits the innate inflammatory tropism of functionalized macrophages to co-deliver gold nano-regulator (AuNPs) and real-time tracer microbubbles (MBs). The AuNPs function dually as high-sensitivity photoacoustic imaging agents, enabling deep-tissue quantification of plaque burden, and potent metabolic switches reprogramming macrophage polarization via lipid and energy metabolism pathways. Concurrently, MBs facilitate real-time ultrasonographic tracking with micron-scale spatial resolution. In vivo studies demonstrate sustained plaque-specific accumulation of MφMB-Au, permitting longitudinal dual-modal ultrasound/photoacoustic imaging for over 24 hours. Ultrasound-triggered payload release induced a 5.3-fold increment of M2-repolarization, driving significant plaque regression. Critically, this approach restored efferocytosis capacity and collagen deposition while evading off-target toxicity. As the first cellular cyborg platform unifying longitudinal multimodal imaging, stimuli-responsive cargo deployment, and metabolic reprogramming, this work establishes a paradigm-shifting theranostic strategy to reverse the core pathophysiology of atherosclerosis.

Mixed-matrix membranes (MMMs) embedded with two-dimensional nanosheets are expected to overcome the ubiquitous limitation of permeability-selectivity trade-off, showing great potential in various energy-related technologies. However, it remains challenging to synthesize high-aspect-ratio nanosheets and precisely manipulate their orientation in a polymer matrix to achieve long-range ordered membranes. Herein, we report a [100]-oriented, defect-free MMM incorporating in-plane aligned zeolitic imidazolate framework nanosheets with exposed (200) facets via a shear-flow-induced alignment technique. The high-aspect-ratio structure, in combination with highly aligned straight channels, enables efficient ion sieving and simultaneously builds an ion transport highway. Molecular dynamics simulations and experimental results corroborated that the [100]-oriented MMMs filled with nanosheets possess high ionic conductivity and ultralow active-species permeability. We further demonstrated their applications in alkaline zinc-iron flow batteries (AZIFBs), achieving an exceptionally high energy efficiency of 82.0% at a current density of 260 mA cm^-2 and excellent stability over 200 cycles, which outperforms all commercial membranes and state-of-the-art membranes reported to date. This approach opens the door to the rational design of next-generation membranes with highly oriented channel architectures for other possible applications beyond energy-related technologies, such as gas separation and water treatment.