Synthesis,Characterization And Applications Of Several Low-dimension Inorganic Functional Materials

Researches on synthesis and characterization of low-dimensional materials and methods for their applications by exfoliation and pillaring have been developed in the field of catalysis and separation.Because the morphology and nano-structure of materials will determine their properties and applications,precisely-controlled synthetic processes are needed to develop a series of low-dimension nanomaterials.It is possible to establish a palette of low-dimensional materials and it has been an emerging toolbox for nanotechnology of functional zeolites and other materials to meet various industrial applications.In this study,a series of low-dimension functional materials are synthesized by employing long-chain organics as structure-directing agents(SDA).And through in-depth exploration of their structures,the applications of those materials in molecular catalysis,membrane separation and heavy metal adsorption are further investigated.Hierarchical micro/mesoporous aluminosilicate zeolites(zero-dimensional and one-dimensional composites)are obtained by a simple temperature-gradient method using a long-chain multi-ammonium surfactant as structure-directing agent.The samples possess a disordered and interconnected micro-and meso-pore structure,in which the mesoporous structure is firstly introduced at lower temperature and then partially converts to microporous zeolite at higher temperature.A relative higher amount of Br?nsted and Lewis acid sites is found in as-synthesized sample.The catalytic performance of the samples is evaluated by the Claisen-Schmidt condensation of benzaldehyde and 2'-hydroxyacetophenone.Outstanding conversion as high as 86%was found in as-synthesized samples,demonstrating the excellent synergistic effect of mesopores for transporting bulky reactants and microporous pores with high acid-catalyzed activities.Long-chain SDA could not only direct the synthesis of hierarchical porous materials but also the multilayer MFI zeolites.The properties and applications of MFI zeolite are strictly dependent on its morphology and size.In order to continually improve the aspect ratio for obtaining ultra-thin MFI nanosheets,a suitable amount of graphene oxide(GO)nanosheets have been added in synthetic gel of MFI zeolite.GO has been considered as a versatile two-dimensional(2D)building block with good thermal and mechanical stability for hybrid nanocomposites or graphene-based soft materials.GO nanosheets,serving as the building blocks for oriented attachment and in-situ nucleation sites,positively and effectively induce the multilayer silicalite-1crystallization process and eliminate the over-growth of MFI crystals during the subsequently preparation.The MFI membrane seeding with as-synthesized high-aspect ratio b-oriented MFI nanosheets exhibits good performance in low-concentration ethanol/water mixture.For further exploring the role of long-chain SDA in the synthesis of low-dimensional inorganic materials,the long-chain imidazolium-based surfactants are designed and assembled cooperatively with silicate clathrate anions to generate magadiite nanosheets,where the imidazole acts as SDA for specific structure,while the surfactant tails regulate the distance of layers.Four different tails are selected among linear alkyl chains(C_nH_2n+1,n=12,16,18,22)to evaluate structure-directing effect with formula of[tail-N⁺C₅H₈N]Br^-.The adsorption performance of these materials were investigated by heavy metals removal,including Cu(II),Zn(II),Pb(II)and Cd(II).Through a controllable interface induction,the as-synthesized samples could overcome diffusion limit compared with conventional rosette-like magadiites.Nanosheet-based magadiites are promising adsorbents,which provide new candidates for heavy metals removal.Sn-MFI directing by cetyltrimethylammonium bromide,long-chain multi-ammonium and long-chain imidazolium-based surfactants has also been synthesized,which could be used for catalysis of glucose conversion reaction.Meanwhile,we also compared these three kinds of organic structure-directing agents induction effect.