Processing polyethylene terephthalate (PET) into functional materials has both sustainable and economic significance. Therefore, this study aims to prepare functional nanofibers using PET, combining electrospun nanofibers with metal–organic frameworks (MOFs), which is an effective solution to increase the added value of functional nanofiltration membranes (NFMs). The surface morphology of PET fibers is successfully controlled by electrospinning parameters and post-treatment. The formation of a uniform coating of CuBTC crystals on the PET surface is induced by a simple and low-cost in situ growth technique. CuBTC@PET was treated to prepare superhydrophobic CuBTC@PET (SCP), thus improving the stability of CuBTC in water and expanding its potential applications. Through a series of optical and thermal characterizations, the porous morphology formation mechanism and MOF in situ growth mechanism of SCP fibers were discussed. Then, the air filtration performance and bacteriostatic properties of SCP nanofiltration membranes were investigated. The as-prepared SCP showed a high water contact angle (146.4°), low-pressure drop (39.7 Pa), and high filtration efficiency (95.3%, 3 μm NaCl), as well as unique, broad-spectrum antibiosis potency against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). This study shows that SCP nanofiltration membranes can be practically applied in high-performance antibacterial filtration membranes.