A disulfonyl chloride monomer having a pendent photoreactive diazoketone functional group has been synthesized in high overall yield (>90%). The synthesis involves a convenient two-step reaction sequence starting from commercially available 6-diazo-5-oxo-5,6-dihydro-1-naphthalenesulfonyl chloride, which was reacted with piperazine then 1,3,6-naphthalenetrisulfonyl chloride to give the disulfonyl chloride diazoketone. Thin-film composite membranes having photoreactive diazoketone moieties as side chains of a polysulfonamide have been successfully fabricated by interfacial polymerization of ethanediamine with the disulfonyl chloride diazoketone on a polysulfone support. The effect of polymerization parameters such as monomer concentration, polymerization time, crosslinking, and surfactant have been systematically investigated in terms of membrane morphology and permeation properties.