A microfibrous matrix with embedded supporting particulates/fibers and chemically reactive materials is provided as a filtration system for the removal of contaminants and other harmful agents from liquid and gaseous streams. Such filter may be used for example to protect the intolerant anodes and cathodes of fuel cells from damaging H2S while simultaneously aiding the selective conversion of CO to CO2 in fuel streams predominated by hydrogen. In general, the reactive materials utilized as well as the supporting matrix of fibers may be broadly selected to remove specific contaminants at specific reaction conditions inherent to the application. Such materials may include chemically reactive materials as high surface area carbons, zeolites, silicas, aluminas, inorganic metal oxides, polymer resins, ZnO, ZnO/Carbon, Pt/γ-Al2O3, PtCo/γ-Al2O3, ZnO/SiO2 and various other catalysts, sorbents or reactants. In an alternative embodiment, entrapped sorbents and other reactants may be used to provide a highly efficient gas and/or liquid separation and purification methodology for gas masks, building filtration systems, and/or as polishing media located downstream of traditional packed bed filtration systems so as to achieve the high volume loading/capacity of the packed bed along with the overall contacting efficiency of the outlet polishing layer.