Water purification has always been a critical yet challenging issue. In this study, an organic-inorganic composite membrane was developed using 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized bacterial cellulose (BC) nanofibers and hydroxyapatite nanowires (HAPNW) with tunable wettability for advanced membrane separation applications. The resulting free-standing TEMPO-BC/HAPNW filter membrane exhibited strong mechanical strength, high flexibility, exceptional deformability, and a high pure water flux of up to 800 L·m