چكيده لاتين
In this research, covalent organic frameworks (COFs) with imine and amine linkages derived from reduction of imine groups were prepared and after characterization with different techniques were used as catalysts for multi-component reactions, sensor for hydrochloric acid and as adsorbent for iodine vapor. Acetic acid was used as catalyst for the preparation of imine-linked COFs, but, in the preparation of amine-linked COFs, formic acid was used as both catalyst and reducing agent (for in-situ reduction of imine-linked COF).
In the first section, the solvothermal reaction of 2,4,6-tris-(4-formylphenoxy)-1,3,5-triazine and p-phenylenediamine in the present of acetic acid and formic acid, were used for the formation of imine-linked COF (IM-COF) and (IR-COF), respectively. Then, the amine-linked IR-COF was used as a basic catalyst for the synthesis of tetrahydro-4H-chromene derivatives via the Knoevenagel-Michael cyclization reaction. The obtained results revealed that the mentioned derivatives were prepared with good to excellent yields and in short reaction times. Also, due to the partial reduction of imine linkages and the presence of amine and imine linkages simultaneously in the IR-COF structure, this COF was used as a sensor for the detection of hydrochloric acid and its mechanism was studied using the (TD)DFT PBE/DNP+ computations. According to the investigations, IR-COF with a lower detection limit (34.6 mg.L-1) compared to IM-COF (61.9 mg.L-1) shows a better performance in HCl detection.
In the second section, considering the environmental impact of iodine, the adsorption of iodine vapor over the COFs was investigated. At first, the reaction of 2,4,6-tris-(4-formylphenoxy)-1,3,5-triazine and 4,4ʹ,4"-(1,3,5-triazine-2,4,6-triyl)trianiline in the presence of acetic acid and formic acid, the COFs were prepared with imine (IL-COF) and amine (AL-COF) linkages, respectively. The prepared COFs were characterized by different analytical techniques and then were used for iodine vapor adsorption. The experimental results show that the iodine adsorption capacity was increased from 2.7 g.g-1 in IL COF to 5.0 g.g-1 in AL-COF. It has been also found that, iodine mostly adsorbed as I_2 over IL-COF and as I_3^- over AL-COF. Also, for a better understanding of the adsorption mechanism, the adsorption types of different iodine species over the model COFs were studied by the (TD)DFT-B3LYP/LANL2DZ computations. It was found that I^- acts only as an electron donor, regardless of the adsorption sites and linkage type. Also, I_2 acts as an electron acceptor for the COF model with amine linkages and as electron donor for the COF model with imine linkages. Due to the higher molecular length of I_3^- it acts as both an electron donor and an electron acceptor for the COF model with amine linkages, while acting as an electron donor for the COF model with imine linkages.
