Abstract: Polymer-bound photosensitizing catalysts are effective in the heterogeneous catalysis of various photosensitized chemical reactions, such as photooxidation reactions, photodimerization reactions, and photocycloaddition reactions, and are thereafter readily separated from the reaction medium and reaction products by simple filtration. The polymer-bound photosensitizing catalysts comprise the nucleophilic displacement reaction product of (A) a polymeric material having attached thereto an available leaving group which is capable of being displaced in a nucleophilic displacement reaction with a nucleophilic reagent and (B) a photosensitizing catalytic compound containing in its molecule a nucleophile which is capable of displacing the leaving group attached to the polymeric material in a nucleophilic displacement reaction.