(3,3)-Connected Triazine-Based Covalent Organic Frameworks for Efficient CO₂ Separation over N₂ and Dye Adsorption

Covalent organic frameworks (COFs) are a promising class of adsorption and separation materials that can meet the needs of ecological sustainability, such as the removal of carbon dioxide and organic dyes. The two synthesized (3,3)-connected triazine-based COFs demonstrate high specific surface area and good thermal and chemical stability. COFZ1 shows good CO₂ adsorption selectivities for different CO₂ and N₂ volume percentage systems at 273 K and 1 bar, with an ideal adsorbed solution theory (IAST) CO₂ selectivity (i.e., separation factor) of 35.09 for the simulated flue gas component and a CO₂ adsorption capacity of 24.21 cm³ g^-1. In the aqueous dye solutions, both COFs present good adsorption performance for the selected dyes, and the maximum adsorption capacities of COFZ1 for methylene blue (MB) and gentian violet (GV) reach 510 and 564 mg g^-1, respectively. Each of the two COFs shows a high anti-interference performance and excellent recyclability. The adsorption capacities of two COFs for RhB (Rhodamine B), MB, and GV hardly vary with pH values and salt concentrations. The adsorption behaviors of the two COFs for dyes follow Langmuir isothermal adsorption and quasi-secondary kinetic adsorption, approaching monolayer adsorption and chemisorption.