Bifunctional FeZr cyanide frameworks modified with Pluronic F127 and amine groups for CO2 adsorption: Performance and mechanism

Amine-modified adsorbents exhibit remarkable potential for efficient CO 2 capture. In this study, a series of amine-based bifunctional solid adsorbents for CO 2 capture was synthesized via an impregnation method. Fe Zr cyanide frameworks were first functionalized with Pluronic F127, followed by the immobilization of diethanolamine (DEA) and tetraethylenepentamine (TEPA) at different loadings (20–40 wt%). Among the resulting materials, FZ(F)-D35% (DEA) and FZ(F)-T35% (TEPA), exhibited the maximum CO 2 adsorption capacity at 45 °C, reaching 1.846 and 2.377 mmol·g −1 . Compared with the unmodified material (FZ), which exhibits an adsorption capacity of 0.989 mmol/g, they increased by 47% and 59%, respectively. After 6 adsorption-desorption cycles, FZ(F)-D35% and FZ(F)-T35% still retained 93.4% and 95.2% of their original capacities, respectively, exhibiting excellent cycling stability. Kinetic analysis indicated that the adsorption process followed the Avrami model (R 2  = 0.999), suggesting a dual mechanism involving both physisorption and chemisorption. Infrared spectroscopy further confirmed the formation of carbamate and hydrogen bonding during the CO 2 adsorption, highlighting the critical synergistic role played by amine groups and hydroxyl groups in the CO 2 adsorption mechanism. It can therefore be inferred that the CO 2 adsorption mechanism is consistent with the zwitterion mechanism. These findings highlight the potential of amine-functionalized Fe Zr cyanide frameworks as robust, regenerable adsorbents for moderate-temperature CO 2 capture.