Infrared spectroscopy is used to monitor the competitive adsorption/desorption behavior of the nerve gas simulants, dimethyl methylphosphonate (DMMP), trimethyl phosphate (TMP), methyl dichlorophosphate (MDCP), and trichlorophosphate (TCP) on silica. All four compounds molecularly adsorb via hydrogen bonds (H-bonds) with the surface hydroxyl groups. The adsorption strength depends on two factors: the specific functional group H-bonded to the surface hydroxyl groups and the number of such bonds per molecule. It is shown that the phosphonates are molecularly displaced from the silica surface by chemical displacers. By judiciously selecting chemical displacers as dictated by the two factors, (i.e., type and number of functional groups H-bonded to the surface silanols) it is possible to selectively and sequentially dislodge each of the four phosphonate compounds adsorbed on silica. Specifically, it is shown that the relative adsorption strength of the phosphonate compounds and the chemical displacers (labeled A-C) follows the order: TCP < MDCP < A < DMMP < B < TMP < C, where A = triethylamine (TEA), B = 2-pyridyl acetonitrile (2-PyAN), and C= ethylenediamine (EDA). AM1 semiempirical calculations show that the toxic nerve agent, sarin, would position itself between MDCP and DMMP in the above order. The implications of using chemical displacers in filtering applications with metal oxide based sensors are discussed.