Preparation of Organic Amine-Functionalized HKUST-1 and Study on Its CO2 Adsorption Performance and Mechanism

The excessive consumption of fossil fuels has triggered a dramatic surge in CO 2 emissions, prompting the development of diverse mitigation strategies. Among these, the functionalization of metal–organic frameworks (MOFs) with polar amine moieties has emerged as a promising approach to substantially enhance their CO 2 capture capacity. In this study, HKUST-1 was synthesized via a solvothermal method and then modified with three different amines (DEA, TEPA, and PEI) by impregnation to prepare a series of solid amine adsorbents. The effects of the amine type, amine loading, and environmental parameters, including temperature, gas flow rate, CO 2 concentration, and humidity, on the CO 2 adsorption performance were systematically studied. Thermal stability, cycling performance, and adsorption kinetics were also evaluated. The results show that the PEI-modified adsorbent exhibits the best performance, with an optimal amine loading of 20%. Excessive amine loading leads to pore blockage and reduces adsorption capacity. Compared to unmodified HKUST-1, PEI20@HKUST-1 shows a 92% enhancement in CO 2 adsorption, attributed to PEI's bidentate adsorption mechanism and flexible polymeric chains, which contribute to a high amine utilization efficiency. Among the environmental factors studied, higher temperatures lower the CO 2 uptake due to thermodynamic constraints, whereas increasing flow rate and humidity first promotes and then suppresses adsorption. The optimal adsorption conditions are identified as 30°C, 20 mL min −1 flow rate, and 45% relative humidity. Moreover, PEI20@HKUST-1 displays good thermal stability and excellent cycling performance, retaining 88% of its initial adsorption capacity after 15 consecutive adsorption–desorption cycles. Kinetic analysis confirms that the adsorption process follows the Avrami model, which indicates a combined physisorption and chemisorption mechanism.