Targeted Synthesis Of Novel3-Dimensional Porous Organic Frameworks And Their Functional Properties

Recently, porous organic frameworks (POFs) as a new kind of porous materials,have attracted a lot of attentions because of their high specific surface areas and lowdensities. The diversities of synthetic methods and skeleton flexibilities which couldbe easily modified by incorporating different functional groups into the frameworksmake POFs great candidates for gas sorption, separation and catalysts carriers. Andthe introduction of reticular chemistry makes the synthesis of POF materials moretargeted. Here, we reported the targeted synthesis of a series of three-dimensional(3-D) POFs, which were prepared by carefully selecting the rigid organic monomerswith different structural characteristics as the basic building blocks. Also the organicpolymerization reactions play an important role in the POF materials synthesis. Thisproject aims to explore how to design and synthesis3-D POF materials with specificstructures and application performances under the guidance of reticular chemistry. Atthe same time, in order to expand the applications of POF materials in real life, westudied the synthesis of low-cost POF materials.Firstly, we reported the targeted synthesis of a micro–mesoporous hybridmaterial PAF-12, which is derived from octaphenylsilsesquioxane as basic buildingunits via Suzuki cross-coupling reaction. Thermogravimetric analysis shows thatPAF-12is thermally stable up to500oC in air condition. According to Ar sorptionisotherm, the network of PAF-12shows classic type IV isothermand also exhibits a sharp uptake at low relative pressures indicating micro–mesoporous texture. The poresize distribution of PAF-12calculated fromnon-linear density functional theory givesonly two clear narrowpeaks centered at1.57and3.17nm. To the best of ourknowledge, PAF-12is the first hybridmaterial containing both micropore andmesopore reported for silsesquioxane-based materials. Additionally, PAF-12exhibitshigh adsorption abilities for organic chemical pollutants such as benzene andmethanol. The effects of different solvent systems to synthesize PAF-12were alsoinvestigated and the optimal condition was found out.Secondly, we presented the targeted synthesis of a series of low-cost porousaromatic frameworks (PAF-7, PAF-8and PAF-9) employing tetraphenylmethane andits silicon and germanium analogue as basic building blocks of the framework viaFourier alkylation reaction. These PAF materials exhibit permanent porosities, highthermal and chemical stabilities, and excellent carbon dioxide sorption abilities.Among these three PAF materials, PAF-7with carbon certer exhibited the highestsurface area along with the highest carbon dioxide sorption amount.Finally, via Fourier alkylation reaction, we obtained two PAF material PAF-7-NH2and PAF-7-OH, to whose frameworks the amine and hydroxy functional groups weresuccessfully attached. According to the FTIR spectra, the characteristic absorptionpeaks of amine and hydroxyl group were clearly shown. Also the XPS spectraconfirmed exist of amine and hydroxyl group in PAF frameworks. Both of thenetworks exhibit excellent thermal and chemical stabilities and high surface area.Compared to the non-functianlised framework PAF-7, PAF-7-OH presentedconsiderably increased absorption ability to carbon dioxide by40%.