In the first part of this study, two covalent organic frameworks (COF) based on benzamidazole (COF-BI-1 and COF-BI-2) were synthesized. The monomer needed for the synthesis of these two covalent organic frameworks was formed, respectively, from pyromellitic dihydride and perlin-tetracarboxylic anhydride reactions with 5-amino-isophthalic acid and identified by FT-IR. The resulting products were reacted with aminobenzidine and polyphosphoric acid, and two COFs were synthesized based on benzimidazole. The synthesized porous covalent organic frames were identified with analyzes, FT-IR, XRD, FE-SEM, TEM, TGA, BET, as well as CO 2 absorbing and elemental analysis. Based on the data obtained from the CO 2 adsorption, COF-BI-1 and COF-BI-2 cavities were measured 426.3 and 257.7 m 2 / g. Two porous covalent organic structures were synthesized by the Friedl-Kraft's reaction in mild conditions. Friedel-Kraft's reaction was carried out in a sample between cyanuric chloride and trifenyl methane, and in another sample between fluorine and cyanuric chloride, this reaction was carried out. The synthesized COFs were identified by analyzes of FT-IR, XRD, FE-SEM-EDX, TEM, TGA, BET and elemental analysis. These four types of synthesized COFs, such as similar covalent organic networks, have a widespread network structure and they have high levels and porosity. The graph of the TGA analysis showed the high thermal stability of the synthesized COFs. In the second step, COFs based on benzimidazole were suspended in various solvents and fluorescence was taken. Suitable solvent was selected, then various cations were solved in the mixture of COF and solvent, and fluorescence was taken. The results showed that by adding 10 ?l Fe 3+ to the mixture of COF and solvent, the intensity of fluorescence was clearly reduced, So, sensitivity of two COF-BI-1 and COF-BI-2 to Fe 3+ far more than Other cations. Thus, they can be used as a sensor to detect Fe 3+ .
