Superhydrophobic Nanoporous Covalent Organic Frameworks Decorated on Stainless Steel Nets for Oil/Water Separation

The discharge of oily wastewater poses a serious threat to human health and the ecological environment. The development of effective oil–water separation techniques is critical to addressing this issue. Herein, a side-chain engineering strategy was proposed to construct nanoscale covalent organic frameworks (COFs) decorated stainless steel nets (SSN) with tunable wettability (SSN@COFs-C) via the introduction of three distinct lengths of alkyl chains. The nanoscale COFs particles were uniformly distributed on the SSN substrate, resulting in a hierarchical surface structure that significantly enhanced the material’s hydrophobicity. Unlike conventional approaches, COFs provide a robust and tunable platform to address challenges in achieving durable superhydrophobic surfaces and overcome key development barriers such as stability and reusability. The SSN@COFs-C exhibited high hydrophobicity (water contact angle of 151.1–157.3°) and self-cleaning properties. The optimal composite was capable of separating immiscible oil/water mixtures with a flux of 6079 L m –2 h –1 and exhibited an oil/water separation efficiency exceeding 99.0%. Moreover, it effectively separated surfactant-stabilized water-in-oil emulsions with a separation efficiency greater than 99% and retained their performance after multiple reused cycles. This work provides insight into the fabrication and application of nanoscale hydrophobic oil–water separation composites.