Enhanced CO₂ adsorption performance on amino-defective UiO-66 with 4-amino benzoic acid as the defective linker

UiO-66(Zr), one of the Zr-based metal–organic frameworks (MOFs), is a potential adsorbent for gas separation owing to its large surface area, easily tunable pore structure, and high chemical/thermal stability. Nevertheless, its CO₂ adsorption amount is somewhat modest in comparison to that of various MOFs. In this study, 4-aminobenzoic acid (PABA) as amino-defective linker was mixed to terephthalic acid at various compositions in a one-step synthesis of UiO-66(Zr) framework. This new restructuring strategy produced defective UiO-66(Zr) with enhanced porosity owing to the missing-linker defects, simultaneously formed –NH₂ groups in the framework, leading to the improvement of the CO₂ capture capacity. At 298 K and 100 kPa, the defective UiO-66 modified with 10% PABA exhibited the highest CO₂ uptake capacity of ~ 2.47 mmol g⁻¹ and ideal adsorbed solution theory (IAST)-based CO₂/N₂ selectivity of ~ 46, which surpass many other CO₂ benchmark adsorbents. This opens a new perspective for developing defective UiO-66(Zr) adsorbent contained amine functional groups, which can improve CO₂ separation performance.