A facile, environmentally benign approach has been developed for the preparation of dynamic, multiresponsive, and self-healing hydrogels from inexpensive bamboo pulp, poly(vinyl alcohol) (PVA), and borax. The microfibrillated cellulose (MFC) reinforced PVA−borax hydrogels were produced through a onepot route in conjunction with ball milling and physical blending in tandem in aqueous medium. In this way, MFC particles could be efficiently generated and well-dispersed in a polymer matrix, and they have been verified by scanning electron microscopy. The rheology analysis indicated a close relationship between the mechanical strength and the MFC loading and ball milling time. Due to the dynamic equilibrium of the didiol−borax linkages and the reinforcement of MFC fibers, the hydrogels showed enhanced self-healing behavior and mechanical stiffness, which was also supported by rheology analyses. In addition, the hydrogels were found to be sensitive to the pH value. The hydrogels present a solvent or gel state with the change of pH value, and this sol−gel transfer can be repeated while maintaining the shape, further demonstrating the dynamic reversible behavior of the hydrogels.
Oxidation of alcohols is a fundamental transformation related to our daily life. Traditional approaches with at least one stoichiometric amount of oxidants are expensive and cause serious environmental burdens. There are many reports on the aerobic oxidation of simple alcohols such as alkyl or phenyl carbinols and allylic alcohols, which used oxygen or air as the environmentally benign oxidant forming water as the only by-product. However, no such protocol has been reported for allenols and propargylic alcohols. Thus, it still highly desirable to develop efficient room temperature oxidations of alcohols with a wide scope including allenols and propargylic alcohols. In this paper, an efficient and clean aerobic oxidation of so far the widest spectrum of alcohols using 1 atm of oxygen or air, producing aldehydes/ketones at room temperature in fairly high isolated yields mostly within a couple of hours is described. It is interesting to observe that the reaction has been efficiently expedited by a catalytic amount of sodium chloride in easily recoverable 1,2-dichloroethane. A mechanism involving NO and NO 2 has been proposed based on the results of the control experiments and GC-MS studies of the in-situ formed gas phase of the reaction mixture.
Crystalline carbon nitride (CCN)-based semiconductors have recently attracted widespread attention in solar energy conversion. However,f urtherm odifying the photocatalytic ability of CCN alwaysr esults in at rade-off between high crystallinity and good photocatalytic performance. Herein, af acile defecte ngineering strategy was demonstrated to modify the CCN photocatalysts. Results confirmed that the obtained D-CCN maintained the high crystallinity;a dditionally,t he hydrogen production rate of D-CCN was approximately 8times highert han that of CCN. Particularly,i tc ould produce H 2 even if the incident light wavelength extended to 610 nm. The significantly improvedp hotocatalytic activity could be ascribed to the introductiono fd efects into the CCN polymer network to form the midgap states, which significantly broadened the visible-light absorption range and accelerated the charge separation for photoredox catalysis.Photocatalytic H 2 production has attracted substantial attention as ag reen route to convert solare nergy into renewable energy,a nd al arge library of photocatalytic materials has been developed over the past four decades. [1][2][3] One of the emerging photocatalyst is polymeric carbon nitride (PCN), which has been widely studied in variouss olar energy conversion processes owing to its unique physicochemical properties. [4] Like most conjugated polymer photocatalysts, [5,6] the semiconductor properties of PCN result from the presence of the extended conjugated system and largely rely on the extent of its polymerization.H owever,o wing to the limited mobility of the reaction intermediate, the traditional thermal synthesis of PCN alwayss uffers from incomplete polymerization, thus producing an amorphous melon-based structure. [7, 8] In this kind of amorphous structure, neighboring1 Dp olymeric heptazine chains are bridged by hydrogen bonds, which may significantly hinder the charget ransfer across the 2D polymer plane. [9] Thus, constructing highly crystallinec arbon nitride (CCN) with al arger extento fp olymerization is desirable.Recently,aheptazine-basedC CN semiconductor has been constructed by at wo-step ionothermal approach. [10] Owing to its advantageous polymer structure, the CCN polymer exhibits an outstanding H 2 evolution efficiency compared with amor-phousP CN. [11] First, the higher degree of polymerization of the polymerich eptazinesi nC CN can offer unblocked channels for charge transfer across the 2D p-conjugated plane, whichc an efficiently enhancet he intralayer charge transfer and exciton dissociation. Additionally,t he CCN has as horter p-p stacking distance thant ypical melon-based PCN, which would improve the lateral charget ransfer and interlayer exciton dissociation. These advantages make the CCN materials promising candidates for drivingt he solare nergy conversion. Despite progress in this area, the photocatalytic performance of as-prepared CCN is still limited by the unsatisfactory visible-light response as well as the limited chargem obility.F urther optimizing the...
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