Abstract: Particulate matter (PM) is a major air pollutant, posing a serious threat to the ecological environment and human health, especially PM_0.3 particles are small, penetrating and harmful. It is difficult for traditional air filter materials to effectively remove PM_0.3, and they are non-biodegradable, easy to produce plastic pollution and micro plastic hazards. Therefore, a biodegradable MOFilter with high mechanical properties, high surface potential, high PM_0.3 filtration efficiency, low air resistance was developed. The in-situ MOF functionalized polylactic acid fiber membrane was proposed, and the mechanical polarization was combined to enhance the surface charge of the fiber membrane to improve the electrostatic filtration capability. The relationship between the MOF functional time and the comprehensive properties of the fiber membrane was investigated by regulating the MOF functional time. Scanning electron microscopy (SEM) and Energy dispersive X-ray spectrometry (EDS) were used for microscopic characterization. X-ray diffraction analyzer (XRD) and Fourier transform infrared spectrometer (FTIR) were used to analyze the crystal structure. Universal testing machine was used to test the mechanical properties. Electrostatic tester and Dielectric tester were used to detect the surface potential and dielectric constant to investigate the polarization characteristics. The filtration performance and filtration mechanism of fiber membrane were investigated on the self-built filtration test system. The results showed that the PLA-based MOFilter had excellent mechanical properties and filtration efficiency. The tensile strength increases by 27% (4.4 MPa), the elongation at break increases by 6 times (36.1%), the fracture toughness increases by 8 times (1.46 MJ/m³), and the filtration efficiency of PM_0.3 increases by 17.1% without affecting the filtration resistance. The surface potential of the composite fiber membrane is nearly 4 kV at the highest, and the filtration efficiency can be increased again by 4.3%−7.7%. The proposed full-degradation environmentally friendly multifunctional fiber membrane has a broad application prospect in the filtration of ultrafine particles.