Regulation of Nitrogen Site Distribution and Amine Content in IL@ZIF-8 for Direct Air Capture of CO₂

As the CO2 concentration in the atmosphere is relatively low, directly capturing CO2 from the air remains a challenge. Herein, a dual-functionalized strategy is developed to construct a series of IL@ZIF-8 composite materials by regulating the spatial distribution of nitrogen sites of the anion and the amine content of the cation in the ionic liquid (IL). The introduction of functional sites significantly enhances the capture capability of composite materials toward low-concentration CO2. The IL composed of pyrazole (Py) with adjacent nitrogen sites exhibits stronger interaction with CO2 due to its lower viscosity and higher electron cloud density. The IL@ZIF-8 constructed with tetraethylenepentamine (TEPA) as the cation and Py demonstrates optimal CO2 capture capability, which is attributed to TEPA’s balance of abundant amine groups and moderate viscosity. [TEPA][Py]@ZIF-8 exhibits a remarkable dynamic CO2 capture capacity under simulated air conditions, and in situ FT-IR analysis reveals its reversible adsorption mechanism. This study provides a new strategy for the development of novel adsorbents for low-concentration CO2 capture.