Design,Synthesis And Properties Of Crystalline Porous Organic Materials Based On Schiff-base Reaction

Crystalline porous organic materials consist of covalent organic molecular cages(OMCs)and covalent organic frameworks(COFs).Most of OMCs and COFs are constructed via dynamic covalent chemistry(DCC).Either of them possesses the advantages of light weight,high surface area,good stability,designable structure and controllable functionality which shows promising applications in gas storage and separation,catalysis,sensing,energy storage etc.However,there are still lots of problems in OMCs and COFs that remains to be solved.For OMCs,the first target is to solve the problem of low yield and complicated purification.Secondly,it is necessary to overcome the difficulties of functionalization and the construction of OMCs with large cavities for further application.For COFs,the expansion of the building blocks,the incorporation of functional groups,and the exploration of new application are highly desirable in this field.Based on this,we designed and prepared a series of monodisperse OMCs,and then to two-dimensional,three-dimensional frameworks via Schiff-base reaction.Though the elaborate structural design,we achieved the efficient synthesis and oriented functionalization of OMCs,and further explored the relationship between their structure and properties.The main research results are as follows:1.Via template-directed imine condensation reactions,we have constructed covalent porphyrinic cages with different spacer lengths,in which the cage compounds have been conveniently synthesized in quantitative yields at room temperature.The single crystals of the target molecular cages were obtained by diffusion method and further analysis of the structures was conducted through X-ray single crystal diffraction.This solves a large number of the problems in the construction of OMCs such as complex synthetic steps,low yields,and difficulties in purification.2.We found that the size of the template in the center determines the cavity size of OMCs.Then,by selectively choosing the templates and adjusting the length of diamine spacers,another two cages with larger sizes could be formed in one-step with quantitative conversion.From the successful preparation of OMCs,we believe that the template-directed imine condensation reaction can be used generally to synthesize OMCs of varying sizes.Once the template was removed,we may obtain porous cages with varying cavity sizes,which may enable us to further investigate their applications for encapsulating different guest molecules.3.Though bottom-up strategy,we introduce an electron-deficient functional group into OMCs and synthesized the triazine-based[4 + 6]cage in one-pot reaction.The crystal structure and permanent porosity of the triazine-based cage has been investigated by X-ray diffraction and nitrogen sorption measurement,respectively.Moreover,the cage compound exhibits high selective adsorption of CO2 over N2 due to the abundant imine groups and suitable cavity size.4.There are many deficiencies for OMCs in the practical application,such as low chemical/thermal stability and inconvenient recycling.While the structural uniqueness of COFs has brought these new materials great potential for advanced applications.For example,COFs as photoelectrically active materials have attracted extensive attention.One of the key aspects in electroactive COFs yet to be developed is the expansion of optoelectronic groups and how to increase the conductivity.We have synthesized an electroactive COF containing the TTF monomer for the first time.Moreover,we clearly demonstrate that the well-defined TTF-COF shows high thermal stability and permanent porosity,and it is amenable to doping with iodine,which could improve the conductivity of TTF-COF bulk samples.This novel system provides a new way to prepare well-ordered conjugated TTF materials and may find applications in various fields from electronic devices to energy storage.5.The efficient construction and functionalization of three-dimensional COFs is a key research direction in the field of COFs.We report the design and synthesis of an AIEgen-based 3D covalent organic framework(3D-TPE-COF)for the first time.Interestingly,3D-TPE-COF emits yellow fluorescence upon excitation,with a photoluminescence quantum yield of 20%.Moreover,by simply coating 3D-TPE-COF onto a commercial blue light-emitting diode(LED),a prototype white LED(WLED)was fabricated.