Layered Double Hydroxide Buffer Layer-assisted Preparation Of High Performance Metal-organic Framework Film

Layered double hydroxide(LDH)represents a two-dimensional material compound composed of brucite-like sheets and charge compensating interlayer anions.Metal organic framework(MOF)represents a series of crystalline microporous materials composed of metal ions(clusters)and organic ligands.MOF has rich chemical composition,large specific surface area,diversified topological structure and adjustable channel size.As an emerging functional material,potential application of MOF materials in gas storage and membrane separation has developed vigorously in recent years.Alternatively,the development of MOF film represents another important research direction in this field.This article mainly studies on the use of LDH buffer layer to facilitate the formation of high performance MOF films(including ZIF-8 and Prussian Blue)to explore their potential applications as anti-corrosion coatings,nanofiltration membranes,and ion sieving membranes.(1)Through partial conversion of Zn Al-NO₃ LDH buffer layer,a ZIF-8-Zn Al-NO₃LDH composite film was successfully prepared on the Al plate.Experimental results showed that compared with pure ZIF-8 film,the grain size of ZIF-8-Zn Al-NO₃LDH composite film is reduced,and the grain boundary defect density is reduced accordingly.The DC polarization test results showed that owing to the protection of ZIF-8-Zn Al-NO₃LDH composite film,the polarization current density of the Al plate experienced three orders of reduction,which vividly confirmed that the excellent anti-corrosion capacity of prepared ZIF-8-Zn Al-NO₃LDH composite film.(2)Pure polycrystalline PB film was obtained by in situ hydrothermal growth on Ni Fe-CO₃ LDH buffer layer-modified porous?-Al₂O₃ substrate.Through the addition of surfactants under optimized synthetic conditions,morphology of the Ni Fe-CO₃ LDH buffer layer,which served active nucleation sites of PB crystallites,could be well controlled.After controlled in situ hydrothermal growth,finally a continuous PB film was successfully prepared.The dye retention test showed that the retention efficiency of the PB film for Congo red,calcein,and methylene blue were all higher than 99.5%,which indicated that few grain boundary defects existed in prepared PB film.The CV results further showed that prepared PB film possessed a certain selectivity for monovalent metal ions,thereby showing its potential applications in the separating Li⁺from other monovalent metal ions like Na⁺and K⁺.