Covalent organic frameworks (COFs) are an emerging type of microporous crystalline polymers connected by organic units via strong covalent bonds. Due to the well-defined crystalline structure and excellent chemical and thermal stabilities, COF materials are being considered as promising candidates in a variety of applications, such as gas adsorption, catalysis and energy storage. Compared with metal-organic frameworks (MOFs), COFs exhibits lower density due to no existence of heavy metal elements. However, demanding synthesis requirements such as high temperature and long reaction time prevents the development of COFs synthesis in large scale.
In this thesis, interfacial polymerization which is operated under ambient condition is explored for the formation of COFs. COF-TAPB-TFP made from the condensation of 1,3,5-tris(4-aminophenyl) benzene (TAPB) and 1,3,5-triformylphloroglucinol (TFP) and COF-TAPB-TFB made from 1,3,5-tris(4-aminophenyl) benzene (TAPB) and 1,3,5-triformylbenzene (TFB) were firstly synthesized via the interfacial method. COF-TAPB-PDA that contains 1,3,5-tris(4-aminophenyl) benzene (TAPB) and terephthaldehyde (PDA) as building units was interfacial synthesized by using m-cresol as organic phase instead of aggressive 1,4-dioxane and mesitylene. A novel strategy that utilize a sodium alginate layer to control the mass transfer was tested and resulted in COF membrane with improved quality.
X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy and the nitrogen sorption isotherm analysis were performed to characterize the various COFs synthesized from these experiments. These characterizations indicate successful formation of targeted COF membranes at the interfaces.
This work provides a facile and safe strategy to fabricate COFs membrane under ambient conditions. The free-standing membrane can be transferred onto other substrates to explore their potential applications in filtering large molecules in the future.