Enhanced Water Adsorption Performance of UiO-66 Modulated with <i>p</i>-Nitrobenzoic or <i>p</i>-Hydroxybenzoic Acid: Introduced Defects and Functional Groups
Guodong Fu, Ping Wu, Jinguang Yang, Shiping Zhang, Li Wang, Min Xu, Xiulan Huai
Abstract
Adding appropriate modulators can effectively improve the porosity and adsorption performance of UiO-66. Herein, UiO-66 samples were synthesized with p-nitrobenzoic acid (PNBA) and p-hydroxybenzoic acid (PHBA) as modulators. All samples exhibited good crystallinity and thermal stability. The polar functional groups (−NO2 and −OH) and defects were introduced into UiO-66, which significantly improved its water adsorption performance and applications in adsorption heat transformation. With the addition of six equiv PNBA, the saturated water uptake of UiO-66 increased from 0.40 to 0.58 g/g. Also, 4eqPNBA-UiO-66 exhibited the highest water uptake under low relative pressure, which was almost twice that of “low-defect” LD-UiO-66. The addition of PHBA had little effect on the saturated water absorption. However, its highest water uptake at P/P0 = 0.3 is 0.23 g/g, which is equivalent to that of 4eqPNBA-UiO-66. Ten consecutive adsorption/desorption cycles indicated that these samples had good cycle stability.