Ionic Porous Aromatic Frameworks: Design,synthesis And Properties

As an emerging class of porous materials,porous aromatic frameworks(PAFs)have experienced explosive development during the past decade.Researchers have paid extensive attention to PAFs because of its high surface area,diverse structure,high stability and excellent performance.Research on ionic porous aromatic frameworks is on the rise.In this paper,“targeted” design and synthesis of several ionic porous aromatic frameworks with highly porous structures and excellent performances are reported based on the research background of energy and environmental problems under the current social development.At the same time,theoretical calculation is supplemented to further simulate the structures of materials and analyze the mechanism of their properties.Specific research contents are as follows:1.In an effort to develop PAF materials with high adsorption capacity of sulfide and understand the adsorption desulfurization process,we present a viable synthetic approach for a cationic porous aromatic framework material with imidazolium functional groups,referred to as iPAF-1,using a precursor-designed synthetic method and Yamamoto-type Ullmann coupling reaction.Specifically,the precursor-designed approach stoichiometrically introduces functional groups and ensures evenly distributed adsorptive active sites in the products,thus a computational simulation based on molecular dynamics has made application to the functionalized PAF structures possible for the first time.The simulation results agree well with the experimental results of the porous structures and the adsorptive capacity of iPAF-1 for dibenzothiophene(DBT).In particular,iPAF-1 exhibits the highest adsorption desulphurization capacity for DBT compared with all other reported porous materials to date.Meanwhile,with the aid of computational simulation,the effect of binding energy on the DBT uptake during desulphurization was investigated.2.Aiming at insight into the rational design of synergic catalysts and modulating the interactions between functional supports and catalytic sites,a cationic porous aromatic framework as a capturing platform and polyoxometalate anions as conversion materials are separately designed,and their combination is modularly controlled.The resulting composites show higher catalytic activities than the corresponding conversion sites themselves.Notably,the resulting composites uncommonly exhibit increased surface area and enlarged pore openings after the incorporation of nanoparticles,and lead to the promotion of mass transfer within the porous supports.The emergence of a hierarchical structure with increased surface area induced by guest loading is desired in heterogeneous catalysis.The theoretical simulation further explains the mechanism of the hierarchical structure of composite materials,which is consistent with the experimental results.The reciprocal modulation of both capture and conversion materials results in enhanced conversion and increased reaction rate,indicating the successful preparation of synergic catalysts by this separate design approach.3.In order to obtain porous aromatic frameworks with low cost,high stability,high proton conductivity and dynamic response behavior,a common acid-base indicator,bromophenol blue(BPB),has been selected as the main raw material.Two porous aromatic frameworks,PAF-125 and PAF-126,are synthesized by Sonogashira-Hagihara coupling reaction.Varieties of characterization methods have proved that materials have the similar structural switching behavior to bromophenol blue molecule under the condition of acid and base.Proton-conducting research shows that PAFs materials could convert to the sulfonic-based anionic porous aromatic frameworks after alkaline processing and present high proton conductivity and pH-switching proton conduction performance with high recyclability and stability.These PAFs materials have great potential application value in the field of proton exchange membrane for fuel cells.