A dual-scale roughness structure superhydrophobic superoleophilic fabric was fabricated by first etching the microscale fibers with alkali and then dip-coating in a mixed solution of a polymer of intrinsic microporosity (PIM1) and fluorinated alkylsilane (PTES). Scanning electron microscopy analysis showed that the etching process created nanoscale pits on the fiber surface and subsequently formed hierarchical structures on the fabric surface. Coating of PIM1 PTES on the etched fibers significantly lowered the surface energy of the fibers, thus causing the fabric surface to possess superhydrophobicity with a water contact angle of 158 and superoleophilicity with an oil contact angle of 0 degrees. The obtained superwettable fabric was mounted in a leak-proof manner on the open-end glass bottle, like an oil skimmer container. Such a new surface-tension-driven, gravity-assisted, one-step, oil water separation device was used to separate the oil water mixture with a separation efficiency as high as 99.96% after 30 recycles.