The quenching of Zn(II) tetraphenylporphyrin (ZnTPP) triplets adsorbed onto porous silica or NaA zeolite by molecular oxygen in the gas phase was studied at different temperatures by the diffuse-reflectance laser flash photolysis technique. The quenching is enhanced with decrease in temperature (apparent activation energies are within the range -1.5 to -2.0 kcal/mol) and occurs with high rate constants (2.1 x 10(5) to 2.4 x 10(5) Torr(-1) s(-1)). While the ZnTPP delayed fluorescence (DF) is undetectable in evacuated samples, it appears in the presence of O-2. The yield of this oxygen-induced DF of ZnTPP corresponds to 10-20% of the prompt fluorescence in a wide range of O-2 concentration (partial O-2 pressure from 0.001 up to 10 Torr). DF kinetics exhibits a distinct rise part at relatively high O-2 pressure. Experimental results are described in terms of a singlet oxygen feedback mechanism which includes the efficient triplet energy transfer from (ZnTPP)-Zn-3 to O-3(2) and formation of O-1(2) followed by a much more efficient energy transfer from O-1(2) to the neighbor 3ZnTPP with formation of ZnTPP in the excited singlet state. A homogeneous kinetic treatment predicts some of the unique DF peculiarities (namely the apparent quadratic dependence of DF yield on initial amount of 3ZnTPP, obtained by varying the laser pulse fluence, the growth of DF with a first-order rate constant 2 times greater than that of DF decay at high oxygen concentration, and DF decaying at the same rate as 3ZnTPP at high O-2 content or faster at low O-2 content) except the lack of variation of DF efficiency with ZnTPP content on the surface, strongly suggesting the existence of a specific arrangement of ZnTPP molecules. The yield of ZnTPP triplets on the surface depends essentially on the oxygen amount in the narrow pressure range from 0.01 to 0.1 Torr which is ascribed to the specificity of ZnTPP adsorption sites on the surface based on oxygen vacancies type defects.