Particulate matter (PM) pollution is serious human health issue. Various filter technologies have been developed to improve the air filtration efficiency. Recently, nanofibrous membrane filters have received much attention due to its outstanding transparency and high efficiency for PM <= 2.5 mu m (PM2.5) capture/removal compared to conventional micro-structured filters. Although these filters provide high-efficiency PM2.5 capture, obtaining strong PM adhesion via surface engineering remains a challenge. In this study, we demonstrate a high efficiency PM2.5 capture air-filter by electrospun polyacrylonitrile nanofibers (EPNFs). The surface of the EPNFs was modified by oxygen plasma treatment for generating functional groups such as -CONH2, -COOH and -COOR. The EPNFs were utilized as air filter in hand-made PM removal system which is consisted of DC power supply, PM source, PM sensor and PM removal test chamber. The test result showed high air flow and effective air filtration (PM2.5 removal efficiency: 94.02%, pressure drop: 18 Pa, Time to reach the PM level recommended by the World Health Organization (T-WHO (PM2.5)): 15 min, quality factor: 0.1564 Pa-1) compared to commercial filters. The intermolecular interaction between the plasma-treated EPNFs (PEPNFs) and PMs was investigated by density functional theory (DFT) calculations. The PEPNF filter showed high long-term reproducibility in a cycle test with a high PM concentration (over 2,000 mu gm(-3)). The filter was applied as a car interior air purifier using a cigar jack as a power supply, ca. 16 min was required to reach the PM level recommended by the World Health Organization (<25 mu gm(-3)).