4-Nitrophenyl phenylphosphonate is primarily used in organic synthesis as a reagent for phosphorylation reactions. It serves as a key intermediate in the preparation of various phosphonate esters, which are important in the development of pharmaceuticals, agrochemicals, and biologically active compounds. Its application extends to the study of enzyme inhibition, particularly in the investigation of phosphatase and esterase enzymes, where it acts as a substrate or inhibitor. Additionally, it is utilized in material science for the modification of surfaces and polymers to enhance their properties. Its role in research and industrial processes underscores its importance in advancing chemical and biochemical applications.