Ferrocene-linked triazine-based porous organic polymers as multifunctional platforms for CO₂ recognition, separation and utilization

The development of efficient materials that can capture CO₂ and catalyze its conversion into value-added organic compounds is critically important. The concept of CO₂ Capture and Utilization (CCU) is gradually gaining the attention of researchers. In this study, we designed and synthesized ferrocene and triazine-based porous organic polymers (POP), named FC-TPT-POP and FC-TPT-Ph-POP, through a Schiff base reaction for CO₂ capture, and utilized them as catalysts to transform CO₂ and various epoxides into cyclic carbonates via a cycloaddition process. The FC-TPT-POP showed high surface area (797 m² g⁻¹) and microporosity. The presence of high surface area, porosity, and triazine units having nitrogen basic sites showed excellent selective CO₂ capture (3.34 mmol g⁻¹ at 1 bar pressure/273 K, Q _st of 34 kJ mol⁻¹). Both POPs show strong CO₂ selectivity at low pressures due to interactions between nitrogen sites and the highly polar, high-quadrupole CO₂ molecules. FC-TPT-POP outperforms FC-TPT-Ph-POP, achieving a CO₂/N₂ selectivity of about 40 at 273 K. Moreover, it demonstrates outstanding catalytic performance in transforming simple terminal epoxides into cyclic carbonates using CO₂ as a reactant. For example, under mild conditions (120 °C, 400 psi, 8 h), FC-TPT-POP achieved a high conversion of 99.5 % toward propylene oxide (PO). The catalytic effect arises from the synergistic interaction of Lewis basic nitrogen atoms in the triazine units and the metal active sites of ferrocene. Therefore, the development of ferrocene-triazine-based POP catalysts in this study offers a promising strategy for lowering atmospheric CO₂ levels through efficient capture and catalytic conversion.