Disclosed herein are fibers comprising an active material that assists in removing contaminants from fluid. The active material, which forms a coating on the fiber, typically comprises a non-fibrous: nanostructured, metal-containing compound, such as a metal-oxygen compound. A filter media made of such fibers, as well as methods of making the fiber and the filter media are also disclosed. Methods of purifying fluids, such as air, water, and fuels, are further disclosed.