Science China Chemistry最新文献

In lanthanide (Ln) complexes, the oversight of f-electrons and inner-shell relativistic interactions has constituted a critical gap, limiting a nuanced understanding and modulation of their luminescent properties. Addressing this issue, our study introduces a pioneering series of Ln-based metal-organic frameworks (Ln-MOFs), designated as Ln-TCPP, utilizing tetraphenylpyrazine-derived ligand and Ln³⁺ ions (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) to modulate luminescence through advanced synthesis and theoretical analysis. We particularly emphasize the enhancement of Eu³⁺ luminescence in Ln-TCPP, where incorporating Ag⁺ ions to replace [(CH₃)₂NH₂]⁺ within the Ln-MOFs plays a pivotal role. Theoretically, by employing time-dependent density functional theory (TD-DFT) with full-electron relativistic effects, we demonstrate that Ag⁺ ions induce a splitting in the energy levels of Eu³⁺. This splitting effectively reduces the rate of non-radiative transitions, significantly amplifying Eu³⁺ emission intensity. Our findings not only fill a long-standing void in understanding the all-electron relativistic interaction between f-electrons in Ln-MOFs luminescence but also establish a new strategy for controlling and optimizing the luminescent efficacy of these materials for potential applications.

Transformation of the electronic spin states has received significant interest in recent years because of its applications in the magnetic information storage materials and optical response switches. However, it can be formidably challenging to use ultraviolet (UV) light as a contactless stimulus to alter the electronic spin states of the supramolecular cages. Inspired by the approach on the radical cation mechanism of the Scholl reaction and the photocyclization reactivity of tetraphenylethylene (TPE) derivatives, we report two photochromic cages (cage-TPE-1 and cage-TPE-2) that can be photochemically transformed from electron paramagnetic resonance (EPR)-silent to EPR-active form via UV irradiation due to the photo-induced electron transfer process at the TPE moiety. EPR provided a strong single-electron signal with a g value of 2.003 in cage-TPE-1 and cage-TPE-2 but no signal was detected for the pristine samples without the UVexposure. The transformation can be monitored by ultraviolet–visible–near-infrared (UV–vis–NIR) and photoluminescence (PL) spectroscopy. The photogenic radical cage intermediate was unstable in solution resulting in the degradation and intramolecular cyclization of the reactive species, while the radicals were found to be stable and persistent in the solid state due to the spin delocalization, the steric protection of confined cavities, and the oxygen isolation. Both theoretical calculations and spectral measurements suggest that the photogenic radical cage-TPE-2^(•+) experiences photocyclization on the TPE core. Compared with the close-shell cage, the radical cage-TPE-1^(•+) and cage-TPE-2^(•+) exhibit better photothermal conversion performance due to the incubated infrared absorption from open-shell electron feature and reduced band gap.

Ethylene (C₂H₄) and propylene (C₃H₆) produced by methanol to olefin (MTO) technology are important chemical raw materials. However, the purification and separation between C₂H₄ and C₃H₆ mixtures is very challenging. Herein, a novel microporous metal-organic framework (MOF) adsorbent Co₂(OATA)(DPA) was fabricated through mixed linkers of 5,5′-(oxalylbis(azanediyl))diisophthalic acid (H₄OATA) and V-shaped di(pyridin-4-yl)amine (DPA) with –NHCO– and –NH– functional groups, which was endowed with ideal small pore size, large cavity, and interesting C₃H₆ trap constructed by four sets of –NH– groups. Under 298 K and a crucial low pressure (0.05 bar) for the separation in microporous materials, the MOF shows ultra-high C₃H₆ preferential adsorption (97.8 cm³ g⁻¹) and considerable C₃H₆/C₂H₄ selectivity (about 22), representing an advanced material for the reported porous materials with C₃H₆/C₂H₄ separation function. The studies of single crystal X-ray diffraction and simulations showed that the customized pore limitation in the MOF provided stronger multiple attractive interactions with C₃H₆, leading to significant adsorption selectivity in the process of competing adsorption for C₃H₆ and C₂H₄. In one separation step, the MOF generated highly pure C₂H₄ (⩾99.9%) and C₃H₆ (⩾99.6%) products respectively from C₂H₄/C₃H₆ mixtures at different ratios, pressures, and temperatures.

Achieving simultaneous polarization and spin switching at room temperature is essential for advanced multi-state storage and control applications, particularly in magnetoelectrics and electron spintronics, yet such materials are exceedingly rare. Based on polar molecular valence tautomerism of Co^III(3,5-DBcat)(3,5-DBsq)(trans-4-stypy)₂ (1), room-temperature spin and polarization switching was achieved via electron transfer. Notably, the ferroelectric polarization and spin switching in 1 are modulated by both temperature and light. The successful implementation of room-temperature polarization and spin switching in 1 signifies an important advancement toward practical applications.

Accurate signal amplification in living cells is highly important in biomedical research and medical diagnostics. Benefiting from its enzyme-free, efficient isothermal signal amplification ability, hybridization chain reaction (HCR) plays an important role in intracellular signal amplification; however, HCR fails the accurate signal amplification in the situation when the properties of some biological targets and analogues are too similar. Particularly, their signal amplification accuracy for mature miRNAs is unsatisfactory due to the signal interference of precursor microRNAs (abbreviated as pre-miRNAs), which also contain the sequence of mature miRNAs. Herein, we develop the first example of size-selective hybridization chain reaction probe for accurate signal amplification, which achieved accurate and sensitive biosensing of mature miRNAs in living cancer cells. Our probe, termed as qTcage, consists of a DNA nanocage for size-selective responsive to mature miRNAs, as well as a quadrivalent tetrahedral DNA structure for HCR signal amplification. Benefiting from the size-selectivity of DNA nanocage, shorter mature miRNAs (19–23 nt) rather than longer pre-miRNAs (60–70 nt) could enter the cavity to release triggers strand, which activates HCR reaction for fluorescence signal recovery. The probe efficiently reduces signal interference of pre-miRNAs and improves the imaging sensitivity for intracellular mature miRNAs, which was successfully applied for mature miRNAs imaging during drug treatment. Overall, this strategy provides the hybridization chain reaction with the feature of size-selective ability, which holds promise for further accurate signal amplification in biological processes study and clinical diagnostics.

Electrochemical reduction of acetonitrile (ACN) to ethylamine (ETA) is a new strategy for producing high-value chemicals. Herein, the ultrathin nickel sulfide nanosheets (Ni_xS_y NSs) anchored on nickel foam (NF) nanohybrid (Ni_xS_y NSs/NF) were designed as an efficient bifunctional electrocatalyst for the waste conversion. Owing to the introduction of the S element, the ultrathin nanosheet structure, and the three-dimensional architecture, Ni_xS_y NSs/NF simultaneously reveals excellent electrocatalytic activity for both electrochemical ACN reduction reaction (EACNRR) at the cathode and electrochemical sulfur ion (S²⁻) oxidation reaction (ESOR) at the anode. For the EACNRR, Ni_xS_y NSs/NF exhibits a Faradaic efficiency of 95.5% and the ETA yield of 923.1 mmol h⁻¹ g⁻¹ at −0.05 V potential. For the ESOR, the S²⁻ ion is oxidized to the value-added S₈ product, in which the oxidation potential is only 0.16 V at 50 mA cm⁻². Consequently, the assembled Ni_xS_y NSs/NF∥Ni_xS_y NSs/NF electrolytic cell is successfully established for the ESOR-assisted EACNRR system that only needs a cell voltage of 0.32 V to reach the 50 mA cm⁻² current density. This work provides an effective and energy-saving strategy for the co-production of value-added chemicals from pollutants.

The field of polymer mechanochemistry has been revolutionized by implementing force-responsive functional groups—mechanophores. The rational design of mechanophores enables the controlled use of force to achieve constructive molecular reactivity and material responses. While a variety of mechanophores have been developed, this Mini Review focuses on cyclobutane, which has brought valuable insights into molecular reactivity and dynamics as well as innovations in materials. We discuss its reactivity and mechanism, dynamics and stereoselectivity, as well as impacts on material properties.

Two-dimensional (2D) materials are vital for the development of advanced materials in the next-generation energy conversion and storage devices. In-situ liquid-phase transmission electron microscopy (LP-TEM) acts as a powerful tool for characterizing the dynamic evolution of materials under work condition in real time and in operando. Herein, this mini-review highlights the considerable advances in the utilization of in-situ LP-TEM for studying the physical and chemical process dynamics of 2D materials, such as their nucleation growth and phase transformation. The electrocatalytic water splitting reactions and CO₂ electroreduction of 2D energy materials are highlighted. The underlying electrochemical reaction mechanisms of the 2D electrode materials in rechargeable batteries are discussed and summarized. Finally, the current challenges and perspectives for future research are proposed. This min-review aims to inspire and stimulate further innovation and encourage the broader adoption of LP-TEM in exploring the fascinating dynamics of 2D energy materials.