In this study, eco-friendly superhydrophobic (SH) and superoleophilic (SO) poly (3-hydroxybuthyrate) (PHB)-SiO2 bio-nanofiber membrane has been successfully fabricated for oil–water separation. Firstly, silica nanoparticles (SiNPs) have been synthesized via green laser ablation technique. It was placed into PHB matrix in different contents by controlling the time of ablation and then PHB-SiO2 nanofibrous mats were obtained on commercial stainless-steel mesh with various mesh sizes by electrospinning method. The surface morphology and chemical structure of all obtained samples have been characterized by FT-IR, FE-SEM and HR-TEM techniques. It has been observed that SiNPs obtained within 30 min ablation time, with an average size distribution between 10 nm and 200 nm with spherical shape have been uniformly anchored on PHB nanofibers. PHB-SiO2 fibrous membrane has shown superhydrophobicity with maximum water contact angle of 160.23° and superoleophilicity with oil contact angle (OCA) of being nearly 0° in air. Later, SH and SO membranes were directly employed for oil water separation without using any chemical reagent or additional force, and maximum efficiency of separation higher than 99% has been measured. These results has indicated that environmental friendly PHB-SiO2 bio-nanofiber membrane offers high potential for using in gravity-driven oil–water separation.