Fabrication Of Monodisperse Flower-Like Coordination Polymers(CP)Microparticals By Spray Technique

Coordination polymers(CP)are a class of organic-inorganic hybrid materials,which are based on metal ions linked by polydentate organic ligands.The CP family involves two important members:metal-organic frameworks(MOF)and infinite coordination polymers(ICP).Normally,the CP with highly crystalline structures and a well-defined framework are referred to as MOF,and the ones with amorphous structures or without definite crystalline structures are referred to as ICP.CP which possess inherent porosities,high surface and uniform channels have emerged as an intriguing class of porous materials with a high potential for applications in separation,storage,and catalysis.With the increasing demand for multi-functional new materials,nanoµstructures with special morphology have become hotpots in current research due to their potential application in the fields of molecular energy,catalysis,light energy conversion and drug delivery.In these new nanoµ structures,the flower-like particles are attracting more attention due to their large surface and more active sites.Combined coordination polymers frameworks with flower-like nanoµstructures,the flower-like CP microparticals exhibit superior performance over CP and flower-like particles.However,structuring CP at the nano and micro-scales is a nascent field and it is still a challenge to fabricate complex or desired CP nanoµstructures through a facile and controllable approach.Among the researches on CP,considerable efforts have been devoted to the exploration of their nanoµstructures,namely the crystal size,morphology and the shape of crystal aggregates.The flower-like particles with nanoflakes are an intriguing class of nanoµstructures.The flower-like structures could be considered as an aggregation of two-dimensional nanosheets,where the surface of the nanosheets is fully exposed to the environments and facile to be accessed.In this artical,we employed Co2+and 1,4-benzenedicarboxylate acid(H2BDC)as building blocks to fabricate CP flower-like structures by spray technology.The reaction mechanism is metal ion solution was atomized by ultrasonic sounds and then sprayed on the surface of the organic ligands solution.The gentle touch of the droplet and the solution gave rise to a steady interface,where the crystal inclined to grow in the lateral direction and therefore generated the CP nanosheets.Consequently,the resulting nanosheets concentrated in the zone of the droplets,making it possible for the nanosheets to aggregate further.Under appropriate experimental conditions,the nanosheets would be assembled crosswise into the flower-like structures.In this artical,two kinds of flower-like coordination polymers microparticles were successfully prepared by changing the concentrations of reactants,solvents and the parameters of spray equipment,namely Co/BDC MOF flower-like microparticles and Co/BDC ICP flower-like microparticles.The morphology,crystal structure,elementary composition,thermal stability,specific surface area of Co/BDC CP microparticles were characterized and analyzed by SEM,XRD,FT-IR,EDS-Mapping,TG and BET.The experimental results show that the MOF and ICP microparticles possess the similar flower-like structure,which is composed of nanoflakes with smooth surface,and the flower-like microparticles have regular morphology,good monodispersity and thermal stability.In addition,Co/BDC MOF flower-like microparticles prepared by the cycloaddition of CO2 with epoxides have a good catalytic effect.Meanwhile,Co/BDC ICP flower-like microparticles have a good catalytic effect in the p-nitrophenol reduction reaction.As is well-known,the spray is an easy-handle technique and has been widely used in industry.Therefore,our investigation indicated that the utilization of spray is an efficient and industrialized means to fabricate CP nanoflowers,paving a practical way for next-step applications.