The development of effective, stable anhydrous proton-conductive materials is vital but challenging. Covalent organic frameworks (COFs) are promising platforms for ion and molecule conduction owing to their pre-designable structures and tailor-made functionalities. However, their poor chemical stability is due to weak interlayer interactions and intrinsic reversibility of linkages. Herein, we present a strategy for enhancing the interlayer interactions of two-dimensional COFs via importing planar, rigid triazine units into the center of C 3 -symmetric monomers. The developed triazine-corebased COF (denoted as TPT-COF) possesses a welldefined crystalline structure, ordered nanochannels, and prominent porosity. The proton conductivity was � 10 times those of non-triazinyl COFs, even reaching up to 1.27 × 10 À 2 S cm À 1 at 160 °C. Furthermore, the TPT-COF exhibited structural ultrastability, making it an effective proton transport platform with remarkable conductivity and long-term durability.
Bifunctional scaffolds prepared by hydroxyapatite/poly(dopamine)/carboxymethyl chitosan with good osteogenesis and anti-osteosarcoma effect is promising for bone tumor therapy.
Assembling molecular proton carriers into crosslinked networks is widely used to fabricate proton conductors, but they often suffer losses in conduction efficiency and stability accompanied by unclear causes. Covalent organic frameworks (COFs), with well-defined crystal frameworks and excellent stability, offer a platform for exploring the proton transfer process. Herein, a strategy to construct proton conductors that induce conductivity and stability by introducing bottom-up hierarchical structure, mass transport interfaces, and host-guest interactions into the COFs is proposed. The proton-transport platforms are designed to possess hierarchically macro-microporous structure for proton storage and mass transport. The protic ionic liquids, with low proton dissociation energies investigated by DFT calculation, are installed at open channel walls for faster proton motion. As expected, the resultant proton conductors based on a covalent organic framework (PIL 0.5 @m-TpPa-SO 3 H) with hierarchical pores increase conductivity by approximately three orders of magnitude, achieving the value of 1.02 × 10 −1 S cm −1 (90 °C, 100% RH), and maintain excellent stability. In addition, molecular dynamics simulations reveal the mechanism of "hydrogen-bond network" for proton conduction. This work offers a fresh perspective on COF-based material manufacturing for high-performance proton conductors via a protocol of macro-micropores.
The distinct structural properties and osteogenic capacity are important aspects to be taken into account when developing guided bone regeneration membranes. Herein, inspired by the structure and function of natural periosteum, we designed and fabricated using electrospinning a fibrous membrane comprising (poly)--ε-caprolactone (PCL), collagen-I (Col) and mineralized Col (MC). The three-layer membranes, having PCL as the outer layer, PCL/Col as the middle layer and PCL/Col/MC in different ratios (5/2.5/2.5 (PCM-1); 3.3/3.3/3.3 (PCM-2); 4/4/4 (PCM-3) (%, w/w/w)) as the inner layer, were produced. The physiochemical properties of the different layers were investigated and a good integration between the layers was observed. The three-layered membranes showed tensile properties in the range of those of natural periosteum. Moreover, the membranes exhibited excellent water absorption capability without changes of the thickness. In vitro experiments showed that the inner layer of the membranes supported attachment, proliferation, ingrowth and osteogenic differentiation of human bone marrow-derived stromal cells. In particular cells cultured on PCM-2 exhibited a significantly higher expression of osteogenesis-related proteins. The three-layered membranes successfully supported new bone formation inside a critical-size cranial defect in rats, with PCM-3 being the most efficient. The membranes developed here are promising candidates for guided bone regeneration applications.
Imine‐linked covalent organic frameworks (imine‐COFs) represent the most sought‐after class of COFs due to their broad monomer scope and ease of synthesis. Owing to the reversible nature of imine linkages, however, the chemical stability of most imine‐COFs is still far from adequate. In this context, emerging strategies, ranging from linkage chemistry to interlayer interaction, have been employed to construct stable imine‐COFs for their applications in electronics, sensing, and energy storage devices. This Concept article summarizes the latest advances aimed at tuning the structural stability of imine‐COFs. Furthermore, this Concept provides a prospective for the precise design of stable imine‐COFs based on the characteristics of structure, physical properties, and chemical functions, as well as the mechanism of structure locking and stabilization during crystal growth.
Lithium metal batteries with polyethylene oxide (PEO) electrolytes are considered as one of the ideal candidates for next generation power sources. However, the low ambient operation capability and conventional solvent‐based fabrication process of PEO limit their large‐scale application. In this work, a comb‐like quasi‐solid polymer electrolyte (QPE) reinforced with polyethylene glycol terephthalate nonwoven is fabricated. Combining the density functional theory calculation analysis and polymer structure design, optimized and synergized ion conductive channels are established by copolymerization of tetrahydrofurfuryl acrylate and introduction of plasticizer tetramethyl urea. Additionally, a unique two‐stage solventless UV polymerization strategy is utilized for rheology tuning and electrolyte fabrication. Compared with the conventional one‐step UV process, this strategy is ideally suited for the roll‐to‐roll continuous coating fabrication process with environmental friendliness. The fabricated QPE exhibits high ionic conductivity of 0.40 mS cm−1 and Li+ transference number (t = 0.77) at room temperature. LiFePO4//Li batteries are assembled to evaluate battery performance, which deliver excellent discharge capacity (144.9 mAh g−1 at 0.5 C) and cycling stability (with the retention rate 94.5% at 0.5 C after 200 cycles) at room temperature. The results demonstrate that it has high potential for solid‐state lithium metal batteries.
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