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As eries of highly active organoboron catalysts for the coupling of CO 2 and epoxides with the advantages of scalable preparation, thermostability,a nd recyclability is reported. The metal-free catalysts show high reactivity towards aw ide scope of cyclic carbonates (14 examples) and can withstand ahigh temperature up to 150 8 8C. Compared with the current metal-free catalytic systems that use mol %c atalyst loading, the catalytic capacity of the catalyst described herein can be enhanced by three orders of magnitude (epoxide/cat. = 200 000/1, mole ratio) in the presence of ac ocatalyst. This feature greatly narrows the gap between metal-free catalysts and state-of-the-art metallic systems.A ni ntramolecular cooperative mechanism is proposed and certified on the basis of investigations on crystal structures,s tructure-performance relationships,k inetic studies,a nd key reaction intermediates. Scheme 1. The coupling reaction of CO 2 and epoxide.

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Enzymatic polymerization of phenolic contaminants to polyphenolics by H2O2 is an effective method to turn phenolic wastes to useful polymers. However, the sensitivities and the high costs of enzymes always limit their applications in the long-run treatment of industrial wastewater. In this study, a highly efficient CuO-persulfate (PS) system is reported to be a promising candidate for enzyme–H2O2 and shows high reactivity to polymerize various phenolic contaminants to polymers under alkaline conditions with the ratio of PS/phenolics less than 2.0. Compared with the generally accepted mechanism that the oxidizing species of SO4 •– and ·OH generated during PS activation primarily contribute to the oxidation of various organic contaminants, quenching experiments, EPR (electron paramagnetic resonance) analysis and DFT calculations in this study indicate that PS is activated on CuO via a nonradical pathway under alkaline conditions, and the O–O bond in PS is moderately elongated from 1.45 to 1.58 Å. The inversely linear relationship between log k obs and BDEO–H values of various phenolics in the Hammett plot confirms H-abstraction from various phenolics under alkaline conditions. DFT calculations further reveal the formation of phenolic radicals after the activated PS abstracts H from phenolic −OH, followed by subsequent polymerization of phenoxyl radicals to polyphenolics. Characterizations of the oxidation products confirm that more than 80% phenolic contaminants have been transformed to polyphenolics. This study provides a new alternative for recovering various phenolic contaminants from industrial wastewater.

We describe a robust and facile approach to the selective modification of patterned porous films via layer-by-layer (LBL) self-assembly. Positively charged honeycomb-patterned films were prepared from polystyrene-block-poly(N,N-dimethyl-aminoethyl methacrylate) (PS-b-PDMAEMA) and a PS/PDMAEMA blend by the breath figure method followed by surface quaternization. Alginate and chitosan were alternately deposited on the films via LBL self-assembly. The assembly on the PS-b-PDMAEMA film exhibits two stages with different growth rates, as elucidated by water contact angles, fluorescence microscopy, and quartz crystal microbalance results. The assembly can be controlled on the top surface or across all surfaces of the film by changing the number of deposition cycles. We confirm that there exists a Cassie-Wenzel transition with an increase in deposition cycles, which is responsible for the tunable assembly. For the PS/PDMAEMA film, the pores can be completely wetted and the polyelectrolytes selectively assemble inside the pores, instead of on the top surface. The controllable selective assembly forms unique hierarchical structures and opens a new route for surface modification of patterned porous films.

Covalent organic frameworks (COFs) possess fascinating features that have sparked increasing interest as drug carriers in biomedical applications. However, the promising properties of COFs in wound healing have rarely been reported. Herein, a facile one-pot method is reported to prepare a curcumin-loaded COF (CUR@COF) by the condensation reaction and the Schiff base reaction and to further incorporate CUR@COF into polycaprolactone (PCL) nanofibrous membranes (CUR@COF/PCL NFMs) through electrospinning to develop a pH-triggered drug release platform for wound dressing. CUR@COF has a high CUR loading capacity of 27.68%, and CUR@COF/PCL NFMs exhibit increased thermal stability, improved mechanical properties, good biocompatibility, and enhanced antibacterial and antioxidant activities. More importantly, CUR@COF-based membranes show a pH-responsive CUR release profile by protonation under acidic conditions, suggesting the promotion of CUR release from membranes under an acidic extracellular microenvironment. The histopathological analysis and immunofluorescence staining of an in vivo skin defect model indicate that CUR@COF/PCL NFMs can accelerate wound healing and skin regeneration by reducing the expression of inflammatory factors (TNF-α) and enhancing the expression of angiogenesis (VEGF). This work provides a new strategy by employing COF-based drug-encapsulated nanocomposites for wound dressing applications.