Heterogeneous Photocatalytic Systems Based on Fluorinated Tetraphenylporphyrin Supported on Polysaccharide Aerogels

Abstract—Solid-phase photosensitizing systems active in the generation of singlet oxygen (¹O₂) are obtained from fluorinated tetraphenylporphyrin (FTPP) immobilized on polysaccharide aerogels (chitosan and calcium alginate). Immobilization is carried out in a supercritical carbon dioxide (SC–CO₂), or by planting FTPP on an aerogel (AEG) from a solution in chloroform. The kinetic parameters of the oxidation of tryptophan in an aqueous medium and anthracene in SC–CO₂ are found using these photocatalytic systems. It is shown that the immobilization of porphyrin on a chitosan aerogel does not affect the effective rate constant of photooxidation. Active photocatalytic systems for FTPP immobilized on AG of calcium alginate are obtained only by impregnating the polymer with FTPP molecules in SC–CO₂. It is found that FTPP immobilized on both chitosan and calcium alginate aerogels retains its functional activity for 3–4 cycles in model photooxidation processes. Differential thermal analysis is used to explain the differences between the photocatalytic activity of solid-phase aerogel systems containing porphyrin photosensitizers. Treatment with chloroform in particular has almost no effect on the thermooxidative destruction of the FTPP–chitosan aerogel system. A change in the thermooxidative destruction of the catalyst after treating the FTPP–AG system of calcium alginate with chloroform testifies to a change in structure of the system. It is concluded that photostable photosensitizing systems based on aerogels of calcium alginate or chitosan containing fluorinated tetraphenylporphyrins can be used for the photooxidation of organic substrates in both aqueous solutions and a supercritical medium.