Hydrogen uptake in brownmillerite perovskites ${\mathrm{A}}_2{\mathrm{B}}_2{\mathrm{O}}_5$ offers an (electro)chemically accessible route to tune functional properties, but mechanistic understanding and design rules for hydrogen-responsive oxides remain limited. Here, we employ density functional theory (DFT) to quantify how H absorption affects electronic structure, magnetic exchange, and anisotropy in representative ${\mathrm{Sr}}_2{\mathrm{Fe}}_2{\mathrm{O}}_5$ and ${\mathrm{Sr}}_2{\mathrm{Co}}_2{\mathrm{O}}_5$ oxides. We find that hydrogenation introduces a localized ${\mathrm{e}}^{-}$ that stabilizes near the ${\mathrm{H}}^{+}$, with B-site dependent preference. The resulting lattice distortions and redistribution of charge density modify exchange coupling and cant the Néel vector, giving rise to weak ferromagnetism. We also show that absorption energies are highly sensitive to ${\mathrm{H}}^{+}–{\mathrm{e}}^{-}$ arrangements and magnetic order, varying by up to 1 eV across different settings. This sensitivity demands consistent treatment of charge localization and spin states, together with careful choice of computational parameters. Extending to a variety of experimentally reported ${\mathrm{A}}_2{\mathrm{B}}_2{\mathrm{O}}_5$ compositions, we identify candidates with favorable H uptake and uncover a trend linking more favorable absorption to a higher B-site $d$-electron count. We also demonstrate that the preferential ${\mathrm{H}}^{+}$ absorption site in these materials is governed by local O–O separations and lattice flexibility, which describe the ability of the framework to accommodate ${\mathrm{H}}^{+}$-induced distortions. Finally, benchmarks of universal machine-learning interatomic potentials reveal uncertainties of about 1 eV for site-resolved absorption energies, motivating descriptor-based surrogate models and targeted DFT validation. Together, these results establish practical design rules for hydrogen-responsive oxides relevant to iono-electronic devices, sensors, and electrically tunable spin functionality.

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• Density of states
• Electronic structure
• Magnetic coupling
• Magnetic interactions
• Magnetic order
• Resistive switching
• Spin-orbit coupling
• Hydrogenated materials
• Density functional theory
• High-throughput calculations
• Materials modeling