Preparation And Application Of Chiral Ionic Liquid-based Janus Materials

Compared with the traditional organic quaternary ammonium salt phase transfer catalyst,the Janus nanocatalysts at the phase interface can not only accelerate the material transfer between the two phases,but also facilitate the recovery and recycling.They provide an environment-friendly aqueous phase organic synthesis a new way of thinking.In this paper,chiral recognition and light-driven properties were introduced on the classical Janus nanoparticles,respectively.The former improves the stereoselectivity by preparing chiral ionic liquid-based Janus nanosheets for the phase interface reaction.And the latter improves the stereoselectivity by preparing carbon nitride-based Janus nanosheets for the phase interface reaction endowed with light kinetic energy drive.The main work is as follows:1.Natural nicotine-based chiral ionic liquid-based Janus nanosheets were synthesized at the paraffin-water emulsion interface by the sol-gel and emulsion interface self-assembly method.They can emulsify toluene/water to form a stable emulsion,which can be observed uniformly under an optical microscope droplets.The results show that the contact angle of bromonicotine ionic liquid Janus nanosheets is 107°and the contact angle of PW₁₂O₄₀^3-based nicotine ionic liquid Janus nanosheets after ion exchange is 83°.It can form an oil-in-water（O/W）emulsion,and can be used for asymmetric diydroxylation of styrene in aqueous phase.The yield of（R）-phenylethylene glycol can reach 90.6%in 2 h,and the catalyst is easy to separate.The performance of recycling and recycling has not been significantly reduced.2.A chiral tungstic ionic liquid was prepared with 1,12-dibromododecane,S-nicotine and sodium tungstate.Sodium silicate was taken as silicon source.And then functionalized hollow mesoporous silica spheres were prepared by a one-step hydrothermal method.They were characterized by SEM,TEM,FTIR,UV-Vis,N₂adsorption-desorption,XPS,ICP-OES,contact angles,electronic circular dichroism（ECD）,etc.and their catalytic performance was investigated by the dihydroxylation of olefins.The results showed that the diameter of the hollow mesoporous silica sphere is about 100 nm,the BET surface area is 20-53 m~2/g,and the average pore diameter is 7.7-16 nm.The chiral tungstic ionic liquid was successfully embedded in the mesoporous hollow sphere.The spherical solids presented the circular dichroism.The catalyst with n（W）∶n（Si）=0.25∶0.75 performed best during the olefin dihydroxylation reaction,with yield of（R）-phenylethylene glycol of 89.6%and even up to 87% after being recycled for 5 times.Since the contrast sample without tungsten was observed as amorphous nanoparticles,it can be speculated that the tungstic-based ionic liquid displayed a structure-directing effect on the formation of mesoporous hollow spheres.3.Upon the paraffin-water emulsion interface,the nanographitic carbon nitride（g-C₃N₄）was unilaterally grafted with brominated hydrocarbons with different alkyl chain lengths to obtain a series of Janus g-C₃N₄with photocatalytic ability.The results show that among the Janus g-C₃N₄modified with C4,C8,C12 and C16,the Janus catalyst（JCN-12）grafted with C12 behaved the best emulsification,contact angle（75°）and photocatalytic performance.Specifically in a concentrated emulsion of oil/water（1 m L/1.5 m L）,the conversion of benzyl alcohol achieved to 68%（selectivity>99%）with the addition of 20 mg catalyst.On this basis,PW₁₂O₄₀^3-/Janus g-C₃N₄nanosheets were synthesized by ion exchange,with excellent and stable emulsifying properties,and uniform droplets could be observed under optical microscope.They were used for asymmetric dihydroxylation of styrene in aqueous phase.The conversion rate of 2 h can reach 99%,and the selectivity of phenylethylene glycol can reach 90%.