Enol-keto Tautomerism Covalent Organic Frameworks:Synthesis, Characterization And Their Applications In Water Treatment

With regularity channels, high specific surface areas and readily modification abilities, Covalent Organic Frameworks(COFs) have received increasing interest. Recently, they have been developed into the application of gas storage, photoelectricity, drug delivery, catalysis and separation. However, seldom applications in water treatment were reported. There are two critical challenges for making use of COFs in the field of water treatment:1)reversible back-reaction can occur in the presence of ambient humidity, which leads to decompose of the frameworks 2)as COFs are powders, it is hard to prepare a pure COFs membranes with defect-free.This thesis in order probe the application of enol-keto tautomerism COFs in the field of water treatment, and it can be divided into four parts.(1) Enol-keto tautomerism COFs powders:synthesis, characterization and their adsorption performance towards dyes:two kinds of COFs-TpPa COF and TpBD COF with different pore sizes were synthesized by a combination of reversible Schiff-base reaction and irreversible enol-keto tautomerism. Further, TpPa COF and TpBD COF were used as absorbent for dyes in water solutions.The results show that the saturation absorptive capacity towards methylene blue is almost 120mgg-1 under pH=7. Moreover, both of two COFs show excellent reuse ability and water stability.(2) TpPa COF/Cellulose mixed matrix membranes:preparation, characterization and their rejection performance for Congo red:preparation of TpPa COF/Cellulose mixed matrix membranes with different TpPa COF loading and testing their separation performance. The results show that the pore structures in TpPa COF can work as water channel and provide sieving effect.(3) Pure COFs membranes:synthesis, characterization and their rejection performance for Congo red:Firstly, synthesis TpPa COF membrane on the surface of dopamine modified Anodic Aluminum oxide (AAO) and Polyvinylidenefluoride (PVDF) microfiltration membrane. The PVDF based TpPa COF membrane shows excellent rejection performance towards Congo red. Secondary, secondary growth method were used to prepare TpPa COF membrane. The SEM images show that both the method can get compact membranes.(4) The preparation of TpPa COF hollow sphere materials:Firstly, the surface of SiO2 nanoparticles were modified by amine group in order to provide anchors for the building units of TpPa COF. Secondly, TpPa COF growth on the surface of SiO2 nanoparticles result in SiO2/TpPa COF core-shell materials. Lastly, TpPa COF hollow sphere material can be achieved by etching the SiO2 with HF.