Visible Light‐Driven Spatiotemporal‐Resolved Proton Management by Harnessing Merocyanine‐Integrated Hydrogels as Regenerative Photoacid Matrices

Abstract Photomanipulation of the environmental pH plays a crucial role in modulating the reaction kinetics and engineering material functionalities. While conventional merocyanine photoacids offer pH modulability, their practical implementation is fundamentally constrained by aqueous dissolution and laborious regeneration. Here, a transformative strategy is reported through the covalent integration of merocyanine photoacids into hydrophilic polymer networks to construct regenerative photoacid matrices, which stably retain protons in the dark and spatiotemporally liberate them upon illumination. The photoacid matrix overcomes solubility constraints through adjustable merocyanine grafting density while simultaneously enhancing alkaline stability, thereby enabling shape‐governed, diffusion‐controlled proton release kinetics. The universality of this approach has been extensively verified in multiple polymer matrices with variable chemical compositions. Upon straightforward separation and acidic regeneration in the dark, the recovered matrices sustainably maintain robust photoactivated proton release capability. This not only enables programmable control over acid–base indicator discoloration but also guides hierarchical self‐assembly of arylazopyrazole‐based hydrogelators, yielding 3D supramolecular gel architectures with tailored complexity. Furthermore, spatially controlled directional proton liberation are established through synergistically addressing negative phototropic deformation within a low‐density crosslinked photoacid matrix. This work creates a new paradigm for spatiotemporal pH manipulation in the development of autonomous materials through regenerative photoacid matrices.