Redox chemistry of gaseous reactants inside photoexcited FeAlPO4 molecular sieve

The reactivity of ligand-to-metal charge transfer excited Fe centers of FeAlPO4-5 molecular sieve at the gas-micropore interface has been probed by in situ FT-IR spectroscopy. Laser light in the region 350-430 nm was used to excite the metal centers, and reaction was induced between methanol or 2-propanol and O-2 Acetone and H2O are the observed products of the 2-propanol + O-2 system, while the reaction of methanol with O-2 yields formic acid, methyl formate, and H2O as final products. These originate from secondary thermal reaction of initially produced formaldehyde and hydrogen peroxide. The primary step of the proposed mechanism involves one-electron reduction of O-2 by transient Fe+II under concurrent donation of an electron to the hole of framework oxygen by the alcohol molecule. The efficient reaction suggests that the photoreduced Fe center of the molecular sieve has a substantially stronger reducing power than the conduction band electrons of dense-phase Fe2O3 semiconductor particles.