Nonflammable superhydrophobic paper with biomimetic layered structure exhibiting boiling-water resistance and repairable properties for emulsion separation

Commercial paper as an indispensable material in our daily life is extremely easily destroyed by water and fire. And obtaining paper with the writable, non-flammable and superhydrophobic properties is still a challenging issue. Inspired from nature, biomimetic nanowires made from hydroxyapatite (HAP) can be used as raw materials to fabricate functional paper. In this study, we present a superior, fire-resistant and repairable superhydrophobic PFDS-paper@ZnO exhibiting remarkable oil absorption-combustion performance. In particular, the layered structure of the paper might be the reason of its excellent superhydrophobicity even after 20 abrasion cycles with sandpaper (400 cW). In contrast, the common paper was destroyed after 5 abrasion cycles with sandpaper under identical conditions. It was observed that the intrinsic fire-resistant nature of the paper was expected to reduce the risk of fire and might be used as an absorbent for flammable oil. On the one hand, such burnt paper can recover its original superhydrophobicity by facile modification after multiple cycles, achieving the repairable performance of its superhydrophobic surface. On the other hand, the burnt paper without subsequent modification exhibits superhydrophilicity in air and also underwater superoleophobicity, which can be used for efficient surfactant-stabilized oil-in-water emulsion separation. This study expands the potential applications of functional paper, which might be a breakthrough for traditional papermaking industries.