Acetic acid-assisted synthesis of Zr-based metal organic framework for rapid and efficient low-concentration ammonia adsorption

Metal-organic frameworks (MOFs) have been acclaimed as potential adsorbents for gas separation, yet their intrinsic microporosity and site-saturated coordination often lead to slow adsorption kinetics and poor selectivity under low-concentration gas conditions. To address this challenge, we developed an acetic acid-assisted synthesis strategy to engineer Zr-based MOFs (UiO-66-V, V = acetic acid volume) with enhanced Lewis acids sites and porous structure. The optimal UiO-66-2.5 variant achieves an adsorption rate six times higher than that of pristine UiO-66 and superior ideal adsorption solution theory selectivities for 3 % NH 3 /97 % N 2 (745) and 3 % NH 3 /97 % H 2 (6036) at 298.2 K and 1.0 bar. Dynamic breakthrough experiments confirm the excellent regenerative stability and separation performance of UiO-66-2.5, achieving a retention time of 120 min g −1 for a simulated industrial gas mixture (3 % NH 3 /24.25 % N 2 /72.75 % H 2 ), outperforming pristine UiO-66 (84 min g −1 ). Furthermore, the optimized 90 % UiO-66-2.5@PVA pellets exhibit a breakthrough time of 100 min·g −1 , which is comparable to that of the UiO-66-2.5 powder. Moreover, UiO-66-2.5 could maintain 92 % capacity over 10 adsorption-regeneration cycles. Comprehensive characterization studies revealed that the enhanced NH 3 uptake and separation performance originate from the higher surface areas and increased Lewis acids sites in UiO-66-2.5 compared to the pristine material. This work establishes acid-assisted synthesis as an effective strategy for designing MOFs that meet the capacity, kinetics, and stability requirements for industrial NH 3 capture.