Superhydrophobic Metal–Organic Framework Nanocoating Induced by Metal-Phenolic Networks for Oily Water Treatment

Metal–organic frameworks (MOFs) with tailored chemical compositions and topological structures have exhibited good application potential in the fields of adsorption, catalysis, and so on. In our study, an aerogel that is composed of a kapok fiber core and MOF nanocoating was fabricated through growing hydrophobic ZIF-8 on the kapok surface induced by Fe3+-tannic acid networks (FTN). Briefly, kapok, a typical fiber in nature, was first pretreated by NaClO2 solution and then coated by FTN through coordination-enabled assembly/adhesion of Fe3+ and tannic acid. Then, the growth of ZIF-8 nanocoating was triggered by FTN, where the dodecane was in situ anchored on the as-formed ZIF-8, thus forming the ZIF-8*/FTN/kapok aerogel. The resultant aerogel exhibited a lotus leaf-like surface, where ZIF-8 and dodecane, respectively, mimicked the nubs and the wax on the lotus leaf. As a result, the aerogel showed a superhydrophobic surface that exhibited a water contact angle of 162.31°, which could absorb a series of oils/organics with the capacities of 20.0–72.0 g g(sorbent)–1, over 17–40 times higher than ZIF-8* particles depending on the types of oils/organics. Moreover, the aerogel showed superior recyclability, which retained over 75.64% of its original sorption capacity after 50 cycles. By using of our method, the hydrophobic MOF nanocoating could be grown on a broad range of materials, which would broaden the application of MOFs.