Room Temperature Hydroxyl Group-Assisted Preparation of Hydrophobicity-Adjustable Metal-Organic Framework UiO-66 Composites: Towards Continuous Oil Collection and Emulsion Separation

Developing a straightforward and effective hydrophobic modification for metal-organic frameworks (MOFs) under mild conditions is meaningful for MOF applications. Here, a post-synthetic modification approach assisted with metal hydroxyl groups at room temperature is reported to induce hydrophobicity in the hydrophilic UiO-66. The bonding between Zr-OH in UiO-66 and n-tetradecylphosphonic acid (TDPA) is the vital force for the modifier TDPA. Superhydrophobic and superoleophilic composites were constructed for efficient oil-water separation by coating TDPA-modified UiO-66 (P-UiO-66) on commercial melamine sponges (MS) and filter papers (FP) with water contact angles of 153.2 degrees and 155.6 degrees, respectively. The P-UiO-66/MS composite could quickly and selectively absorb oily liquids up to 43 times its weight from water. The P-UiO-66/MS achieved continuous oil collection with high separation efficiencies (>= 99.4 %). In addition, P-UiO-66/FP and P-UiO-66/MS showed high separation efficiencies for water-in-oil emulsions (>= 98.5 %) and oil-in-water emulsions, respectively, with high resistance to low/high temperatures and acid/base conditions. The metal hydroxyl group-assisted post-synthetic modification strategy offers a facile and broad way to prepare hydrophobic MOFs for promising applications in environmental fields.