Two-dimensional lead and tin halide perovskites were prepared by intercalating the long alkyl group 1-hexadecylammonium (HDA) between the inorganic layers. We observed visible-light absorption, narrow-band photoluminescence, and nanosecond photoexcited lifetimes in these perovskites. Owing to their hydrophobicity and stability even in humid air, we applied these perovskites in the decarboxylation and dehydrogenation of indoline-2-carboxylic acids. (HDA) 2 PbI 4 or (HDA) 2 SnI 4 were investigated as photoredox catalysts for these reactions, and quantitative conversion and high yields were observed with the former. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim