Covalent organic frameworks (COFs) are crystalline and microporous organic polymers that are constructed via covalent bonds. Generally, the solvothermal method has been usually utilized to synthesize the COFs in which thermal energy is the driving force to form crystalline COFs. However, this method requires a very long time and gives insoluble powder form. Long time consuming is not proper in perspective of efficiency, and this insoluble COF powder form is difficult to process for further applications. Herein, I synthesized imine-based COF film on the water surface using Xe lamp to overcome these limitations. Because instead of thermal energy, the light source can make molecules become excited states easily leading to dynamic imine condensation reaction which enables early amorphous products to convert to crystalline products, and the water surface can act as an excellent 2D confined platform for thin film to be formed. Imine-linked COF film composed of 1,3,5-Tris(4-aminophenyl)-benzene (TAPB) and terephthaldehyde (PDA) were successfully formed by the aforementioned method, which is confirmed by FT-IR, Raman spectroscopy and AFM analysis. Furthermore, this TAPB-PDA COF film was studied for chemiresistive gas sensors due to the unique properties of COFs such as crystalline structure, high surface area, functionality, and chemical stability. TAPB-PDA COF film was integrated into the gas sensor device and performance was tested for water, ethanol, and acetone vapors. It is noticeable that while acetone was not identified, water and ethanol were detected. This result has been guessed that nitrogen atoms in TAPB-PDA COF may be adsorption sites for water and ethanol molecules through hydrogen bonding interaction and electrical current could flow by intramolecular charge transfer. To understand the exact mechanism of this charge transfer, It seems that DFT calculations such as charge difference calculation and TS calculation should be accompanied.