Rational Synthesis of Functionalized Covalent Organic Frameworks via Four-Component Reaction.

The construction of function-oriented covalent organic frameworks (COFs) remains a challenge as it requires simultaneous consideration of diversified structures, robust linkage, and tailorable functionalities. Herein, we report the rational synthesis of functionalized COFs via a four-component reaction strategy. Through the four-component Debus-Radziszewski reaction, 11 N-substituted imidazole-based COFs with diversified structures were facilely constructed from readily available building blocks. By forming the N-substituted imidazole linkage, these synthesized COFs displayed ultrastability toward strong acids and base. Moreover, the four components reaction allows the rational synthesis of COFs with tailorable functionalities. As an example, the phosphonate-functionalized COF (LZU-530) was rationally constructed for the efficient adsorption of uranium(VI). The uranium(VI) uptake of LZU-530 reaches up to 95 mg·g-1 in 2 M HNO3, which is the highest uptake of the existing organic porous materials under such harsh conditions. Our results highlight the use of multicomponent reaction for the rational synthesis of robust and functionalized COFs toward targeted applications.

Modulated Synthesis of Self-Standing Covalent Organic Framework Films.

The weak interaction of covalent organic framework (COF) nanoparticles makes the preparation of self-standing COF films difficult. Herein, a modulated strategy for the facile synthesis of self-standing COF films with good crystallinity and tunable thickness is reported. As compared with the non-modulated approach, the modulated strategy changes the COF morphology from nanoparticles to nanofibers, enabling the facile preparation of self-standing COF films with improved mechanical properties. The Young's modulus of the self-standing COF film obtained via the modulated strategy could increase by 26 times. Moreover, self-standing LZU-8 film can be used as a membrane for efficient removal of 99 % mercury ions from aqueous solution. Our results open up a new approach to prepare self-standing COF thin films for practical applications.

Constructing Robust Covalent Organic Frameworks via Multicomponent Reactions.

Methodology development of robust linkages is fundamentally important for the synthesis and application of covalent organic frameworks (COFs). We report herein a new strategy based on multicomponent reactions (MCRs) to construct ultrastable COFs. With the one-pot formation of five covalent bonds in each cyclic joint, a series of imidazole-linked COFs were robustly constructed through the Debus-Radziszewski MCR from three easily available components. By reaching a higher level of complexity and precision in covalent assembly, this research explores a new direction in integrating sophisticated reversible/irreversible reactions to construct crystalline porous frameworks.

Punicalagin protects bovine endometrial epithelial cells against lipopolysaccharide-induced inflammatory injury.

OBJECTIVE: Bovine endometritis is one of the most common reproductive disorders in cattle. The aim of this study was to investigate the anti-inflammation potential of punicalagin in lipopolysaccharide (LPS)-induced bovine endometrial epithelial cells (bEECs) and to uncover the underlying mechanisms. METHODS: bEECs were stimulated with different concentrations (1, 10, 30, 50, and 100 µg/ml) of LPS for 3, 6, 9, 12, and 18 h. MTT assay was used to assess cell viability and to identify the conditions for inflammatory injury and effective concentrations of punicalagin. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to assess gene expression of pro-inflammatory cytokines. Western blotting was used to assess levels of inflammation-related proteins. RESULTS: Treatment of bEECs with 30 µg/ml LPS for 12 h induced cell injury and reduced cell viability. Punicalagin (5, 10, or 20 µg/ml) pretreatment significantly decreased LPS-induced productions of interleukin (IL)-1ß, IL-6, IL-8, and tumor necrosis factor-α (TNF-α) in bEECs. Molecular research showed that punicalagin inhibited the activation of the upstream mediator nuclear factor-κB (NF-κB) by suppressing the production of inhibitor κBα (IκBα) and phosphorylation of p65. Results also indicated that punicalagin can suppress the phosphorylation of mitogen-activated protein kinases (MAPKs) including p38, c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK). CONCLUSIONS: Punicalagin may attenuate LPS-induced inflammatory injury and provide a potential option for the treatment of dairy cows with Escherichia coli endometritis.