Metal‐organic frameworks (MOFs) are widely employed in heterogeneous catalysis. Enhancing the catalytic performance of MOFs depends critically on precise structural design. Herein, a pyrrole (named as “Pyr”)‐functionalized UiO‐66 photocatalyst is synthesized, by sequentially defect engineering (via Zr‐site vacancy creation) and Clauson‐Kaas reaction‐mediated pyrrole functionalization. The resulting hierarchically porous (HP) MOF, HP‐UiO‐66‐NH 2 ‐Pyr, exhibits exceptional visible‐light‐driven photocatalytic hydrogen production activity, achieving a hydrogen production rate of 4831.7 µmol g −1 h −1 . This value is more than 10 times higher than that of pristine UiO‐66‐NH 2 (463.2 µmol g −1 h −1 ) and approximately three times higher than that of HP‐UiO‐66‐NH 2 (1736.5 µmol g −1 h −1 ). Combined carrier dynamics analysis and density functional theory (DFT) calculations clearly disclose that defect introduction and conjugation extension synergistically optimize the Zr‐O cluster microenvironment, reducing electron‐hole recombination and enhancing charge separation efficiency. This distinctive microenvironment modulation creates additional photogenerated electron transport channels, prolongs excited‐state lifetime and electron migration rates, and thus notably improves photocatalytic performance. Considering the widespread presence of ‐NH 2 chromophore groups in porous materials, this study establishes a new conjugation‐based modification strategy for precise microenvironmental regulation, ultimately enabling the rational design of high‐performance catalysts with significantly enhanced photocatalytic activity.
Flexible and wearable sensors offer immense potential for rehabilitation medicine, but most rely solely on electrical signals, lacking real-time visual feedback and limiting trainee's interactivity. Inspired by the structural coloration of Cyanocitta stelleri feathers, we developed a dual-mode sensor by utilizing black conductive polymer hydrogel (CPH)-enhanced structural color strategy. This sensor integrates a hydroxypropyl cellulose (HPC)-based structural color interface with a designed CPH sensing component. Highly visible light-absorbing CPH (absorption rate > 88%) serves as the critical substrate for enhancing structural color performance. By absorbing incoherent scattered light and suppressing background interference, it significantly enhances the saturation of structural color, thereby achieving a high contrast index of 4.92. Unlike the faint and hardly visible structural colors on non-black substrates, the HPC on CPH displays vivid, highly perceptible colors and desirable mechanochromic behavior. Moreover, the CPH acts as a flexible sensing element, fortified by hydrogen and coordination bond networks, and exhibits exceptional electromechanical properties, including 867.1 kPa tensile strength, strain sensitivity (gauge factor of 4.24), and outstanding durability (over 4400 cycles). Compared to traditional single-mode sensors, the integrated sensor provides real-time visual and digital dual feedback, enhancing the accuracy and interactivity of rehabilitation assessments. This technology holds promise for advancing next-generation rehabilitation medicine.
Diimine-nickel catalysts usually show low activity and poor polyethylene properties during ethylene polymerization at high temperatures, which can be addressed by precise tuning of the ligand structure. In this study, a series of unsymmetrical 1,2-bis(imino)acenaphthene-nickel(II) complexes bearing a fixed, sterically demanding 2,6-dibenzhydryl-4-(benzhydryloxy)phenylimine and systematically varied N-aryl substituents were synthesized and evaluated for ethylene polymerization. These complexes are well characterized by FTIR, elemental analysis and single crystal x-ray diffraction (Ni2 Et and Ni5 Et). Polymerization behavior was strongly influenced by both cocatalyst choice and reaction conditions, with EASC delivering the highest activity (up to 1.34 x 107 gmol-1h-1) and producing high molecular weight (2.0-11.6 x 105 g mol-1), semicrystalline polyethylene, while MMAO produced more amorphous materials with lower melting points. Of significant note, high-temperature polymerization demonstrated excellent catalyst thermal stability, with maintained activity of 1.8 x 106 gmol-1h-1 and molecular weight of 2.1 x 105 g mol-1 at 100 degrees C. Sterically less hindered N-aryl groups favored higher activity, whereas bulkier substituents promoted chain propagation for higher polymer molecular weight polyethylene. Change of steric substituent resulted in precise control over crystallinity (X c: 5.7 to 80.8%), which showed a strong relationship with the mechanical properties of resulting polyethylene, displaying high tensile strength (up to 11.6 MPa) and elongation at break (up to 586%). Compared to previous unsymmetrical nickel catalysts, these polyethylenes offer enhanced tensile performance, emphasizing the structural control exerted by the catalyst structure on material properties.
Nitrile-based electrolytes offer exceptional oxidative stability for high-voltage cathodes but suffer from reductive instability at lithium metal anodes (LMAs) and poor rate capability. Herein, we report a molecular engineering strategy to overcome these limitations by introducing a benzonitrile-based electrolyte (BNE) to realize long-cycling, high-voltage, and high-rate LMBs. We leverage the unique molecular features of benzonitrile (BN), where the cyano groups dynamically coordinate lithium ions (Li+), the electron-deficient phenyl groups interact weakly with anions, and crucially, the bulky BN molecules compress the Li+ solvation sheath through a spatial site-blocking effect. The steric demand imposed by BN during Li+ solvation, coupled with its ability to simultaneously coordinate Li+ and interact with anions, induces a tighter aggregate (t-AGG) solvation structure, which is confirmed by various spectroscopic techniques and molecular dynamics simulations. Mechanistically, the t-AGG solvation structure eliminates most free BN molecules for enhanced stability at LMAs, accelerates Li+ transport kinetics via increased hopping frequency, and promotes an anion-derived solid-electrolyte interphase. Consequently, BNE enables a 4.5 V NCM811||Li cell to achieve 500 cycles with 80% capacity retention at 5C, setting a benchmark for nitrile-based LMBs. This work provides fundamental insights for designing high-performance nitrile-based electrolytes via precise solvation structure engineering for LMBs.
Multi-resonance (MR) materials based on 1,4-BN-heteroarenes have attracted extensive attention in recent years for their narrowband electroluminescence. Extending the π-conjugation of MR skeletons is a widely adopted strategy to regulate their emission colors, but it inevitably induces structural distortion and undesirable vibronic couplings, thus broadening the emission bandwidth. Herein, we design and synthesize new MR emitters via π-extension of a classic MR backbone (CzBN) and disclose how the twisted structure plays a positive role in reducing the emission bandwidth. Specifically, π-extension of CzBN to form a [5]helicene substructure (BN-5H) induces serious vibrations, while further extending the helicene moiety to build a [7]helicene substructure (BN-7H) suppresses undesirable vibrations by locking the conformation. As a consequence, BN-7H achieves a smaller full-width at half-maximum (FWHM) of 28 nm compared with BN-5H (33 nm) in organic light-emitting diodes and longer device lifetime. These results overturn the traditional cognition of the detrimental effect of highly twisted structures on narrowband emission and offer a new design concept for the future development of narrowband electroluminescence materials.
