Photoinduced charge separation of pyrene in chromium containing silicoaluminophosphate (SAPO-5) microporous materials at room temperature

The photoinduced charge separation of pyrene in chromium containing microporous SAPO-5 materials with ultraviolet irradiation at room temperature was examined. Photoionization of pyrene in Cr containing SAPO-5 results in the formation of pyrene cation radicals that are characterized by electron spin resonance (ESR) and diffuse reflectance spectroscopy (DRS). ESR studies indicate that Cr(V) acts as an electron acceptor. The photoyield and stability of the photoproduced pyrene cation radical were found to depend on the pore size of the microporous material, the concentration, and the oxidation state of chromium ions. The photoyield and stability of the photoproduced pyrene cation are found to be higher than in mesoporous materials investigated in our laboratory earlier. The study thus demonstrates the importance of Cr containing microporous SAPO-5 materials as potential candidates for photochemical conversion and storage devices.