The structural, electronic, redox potential, mechanical, photocatalytic, and optical properties of the Dion-Jacobson-type triple-layered perovskites AMCa2Ta3O10 (AM = Rb, Cs) are investigated via density functional theory (DFT) study. The electronic properties are calculated through HSE-06 functional technique which confirmed the semiconducting behavior with the energy band gap values of 1.67 eV and 1.71 eV for RbCa2Ta3O10 and CsCa2Ta3O10, respectively. The calculated results of redox potential indicate that both materials are favorable for water splitting and as an agent for pollutant degradation. Both studied compounds exhibit a reduced effective mass of electrons, which suggests the high capacity to transfer the charge to the surface, indicative of superior electrical conductivity. Poisson's and Pugh's ratios suggest that both the materials are brittle. Optical parameters are calculated within the energy range of 0–6 eV, which strongly correlates with the energy band gap's high absorption and low reflection in the visible region. Our findings indicate high photocatalytic efficiency in organic pollutant degradation, suggesting the potential for developing advanced photocatalytic devices for water splitting and environmental pollutant decomposition.