Enhanced CO2 adsorption performance of UiO-66 modified by annealing- vapor deposition synergistic strategy

Metal–organic frameworks (MOFs) offer tunable porosity and chemistry for advancing CO 2 capture. In this work, a ‘thermal-annealing–amine vapor deposition' strategy is proposed to synergistically engineer structural defects and uniformly distributed amine functionalities in UiO-66. Controlled annealing generates defect-rich UiO-66 (UiO-66-D) with exposed Zr 6 clusters, while subsequent hydrazine vapor deposition anchors amine groups directly at defective Zr nodes. The optimized material, N 2 H 4 @UiO-66-D, exhibits a markedly increased surface area (1449.36 m 2 /g) and achieves a CO 2 adsorption capacity of 2.60 mmol/g (at 298 K, 1 bar and pure CO 2 )—significantly higher than pristine UiO-66 (1.44 mmol/g at 298 K, 1 bar and pure CO 2 ). Enhanced CO 2 /N 2 separation performance is observed under simulated flue-gas conditions (at 1 bar, 298 K and 15 % CO 2 /85 % N 2 ), with IAST selectivity in the range of 111–33. Cyclic adsorption–desorption tests show no obvious decay in CO 2 uptake after ten cycles. Molecular dynamics (MD) simulations reveal that hydrazine modification increases free volume near defect sites, enhancing local CO 2 density. Density functional theory (DFT) calculations show that CO 2 preferentially adopts a bidentate surface adsorption (‘face-on') configuration at hydrazine-modified Zr defects, with an adsorption energy of −0.33 eV, confirming strong CO 2 activation and favorable binding. This work establishes a mechanistic framework for coupling defect engineering with vapor-phase amine functionalization, providing transferable design principles for the development of MOF-based CO 2 adsorbents.