Design And Synthesis Of Functional Porous Organic Frameworks

Environmental pollution is an important issue in sustainable human development.People give great significance to environmental protection,particularly with regards to increasingly scarce water resources.Water pollution is becoming more and more intense due to the presence of organic and inorganic contaminants.Because a serious threat to human health even in low concentration.Several materials have been developed to eradicate these micropollutants.Though,their slow uptake,poor hydro-chemical stability,and poor recyclability may limit their performance and practical implementations.Besides,the quick and selective response towards the target molecule has become one of the most demanding issues.As an excellent platform for global scientists and engineers to explore new multifunctional porous materials with high stability,porous organic frameworks(POFs)have been developed rapidly in recent years.They have attracted much attention due to their high surface area,diverse structure,and high thermo-chemical stability.However,there are few studies on 2D COFs and hydrophilic PAFs.Based on the research background of environmental issues under the current local development,the main theme or scope of this dissertation was to build and design novel porous organic frameworks with high stability and exceptional performance towards detection and adsorption-based applications.Simultaneously,theoretical calculations were supplemented to further simulate the structure of COF materials.The specific research contents are as follows.1.The association of fluorescent cause?-electron rich monomers(4,4',4'',4'''-(ethene-1,1,2,2-tetrayl)tetraaniline)(ETTA)and 9,10-anthracenedicarboxaldehyde are chosen to construct a new dual luminescent covalent organic framework(DL-COF)of high thermal and hydro-chemical stability by using simple Schiff-base reaction.The resultant crystalline framework contains tetraphenylethylene(TPE)and the classic anthracene units,connected through imine(C=N)bond in rhombic-shaped 2D COF,which provides high fluorescence and active binding sites towards the target analyte.These synergistic functions of the framework units endow the unique platform for chemical sensing as well.Owing to synergistic action,DL-COF unveils the best nitro explosives detection with high sensitivity(?10⁶.M^-1,?10¹⁵.M^-1.s^-1)and selectivity(at ppb level)among previously reported COFs and MOFs based sensors under similar conditions.The DL-COF displays excellent chemical stability,sensitivity,and selectivity in detection performance,which are the most desired features for practical sensors.This is the first investigation of anthracene-based 2D COF for such an application.Particularly,the integration of anthracene unit strategy into the2D framework is not only enhanced the structural variety but led to the tremendous sensing abilities towards nitro explosives.2.As a platform with good stability,porous aromatic frameworks(PAFs)have been widely studied.Due to their high surface area and thermo-chemical stability,they are considered to be a worthy sewage treatment agent.Though,the aromatic nature of PAFs makes their skeletons mostly hydrophobic.This characteristic of PAFs seriously affects the water diffusion rate,resulting in a low adsorption capacity.To overcome this problem,we synthesized a series of hydroxyl functionalized porous aromatic frameworks(PAF-80,PAF-81,and PAF-82)by using the Sonogashira-Hagihara cross-coupling chemical reaction,which exhibits polar sites on the hydrophobic planes,which captivate to investigate adsorption behavior on typical organic micropollutants(bisphenol A,2-naphthol and p-chloroxylenol)in the water system.Among the three synthesized hydroxyls PAFs,PAF82 unveiled the highest BET surface area,polar moieties,and a high degree of conjugation,which led to superb adsorption performance compared to that of PAF-80 and PAF-81 and exceeds most of the reported adsorbents.The good recyclability of PAF-82 is verified by consistent a high removal efficiency towards tested contaminants even after four cycles,which is the most desired feature of any practical adsorbent.Furthermore,significant factors,which play important role in adsorption performance were also discussed.This work indicated the potential of hydroxyl PAFs for excellent adsorption and removal of organic contaminants from the water system.3.To obtain efficient crystalline organic porous materials for the adsorption and separation-based applications.To achieve this aim,a highly crystalline,hydro-chemical stable,mesopores,and of high surface area,2D COF(Dhatab)was synthesized and selected as a scaffold.The unique structure of Dhatab endows hydroxyl groups,which assists in further channel wall modification with long-chain carboxyl groups(F-Dhatab).This work emphasizes the impact of smaller functional groups and longer chain functional groups laced in 2D frameworks towards a specific application.The post-synthetic modification approach,not only modifies the conventional 2D COF material but their structural features and properties are also reformed.Basic structural characterization techniques confirm the successful incorporation of longer chain carboxyl groups into the COF wall using a metal-free ring-opening reaction.This work not only investigates a general method for a facile and efficient functionalization of 2D COFs but also promotes functionalized COF materials into an excellent scaffold for desired environmental-related applications.