The demand for clean, environmentally friendly energy has been steadily increasing throughout time. Hydrogen has the potential and is acknowledged as one of the most effective solutions for addressing this requirement. In this manuscript, we have investigated theoretically the photo-catalytic and hydrogen storage capacity of cesium-based perovskite hydrides Cs2Tl \(\:{\text{B}}^{{\prime\:}}\) H6 ( \(\:{\text{B}}^{{\prime\:}}\) =In, Ga) and the physical characteristics are evaluated using the FP-LAPW technique. Modified Becke-Johnson potential is utilized to deal the exchange-correlation terms. The structural analysis depicts complete structural stability of both hydrides at room temperature. The elastic constants for cubic Cs2Tl \(\:{\text{B}}^{{\prime\:}}\) H6 ( \(\:{\text{B}}^{{\prime\:}}\) =In, Ga) is evaluated using the Thomas Charpin approach. The mechanical properties revealed that both hydrides possess ductility and are extremely delicate. The sound velocities for crystallographic planes [100], [110] and [111] are also computed for Cs2Tl \(\:{\text{B}}^{{\prime\:}}\) H6 ( \(\:{\text{B}}^{{\prime\:}}\) =In, Ga) using elastic constants. Semiconducting behavior is revealed for both hydrides with indirect bandgaps of 1.44 eV for Cs2TlInH6 and 1.58 eV for Cs2TlGaH6. The optical analysis revealed high polarization and dispersion of light in the visible and UV region, making these hydrides viable for optoelectronic applications. Furthermore, the photocatalytic study of both hydrides demonstrated excellent potential for hydrogen extraction. The hydrogen storage capacities for Cs2Tl \(\:{\text{B}}^{{\prime\:}}\) H6 ( \(\:{\text{B}}^{{\prime\:}}\) =In, Ga) are also assessed using the gravimetric and volumetric storage capacities, which revealed their suitability for material based hydrogen storage.
