Adaptive Amorphous‐Crystalline Interfacial Coupling Enables Stable Lattice Strain Engineering for Enhanced Solar‐Driven H 2 Conversion

Lattice strain engineering has emerged as an effective route for tailoring surface electronic structures and improving photocatalytic activity. However, achieving stable and spatially uniform strain modulation remains challenging since conventional approaches are often constrained by compromised integrity, coherence‐strain trade‐offs, and defect‐induced charge recombination. Herein, we establish an adaptive amorphous‐crystalline interfacial coupling strategy that enables lattice strain engineering while concomitantly directing charge flow. By integrating hexagonal ZnIn 2 S 4 with amorphous CoO, spontaneous interfacial Co─S bond formation and adaptive structural rearrangement of the amorphous phase cooperatively generate and stabilize uniform compressive strain within the crystalline lattice. The resulting compressive strain downshifts the p ‐band center of surface sulfur atoms, optimizes the adsorption free energy of H * intermediates, and substantially lowers the kinetic barrier for the hydrogen evolution reaction. Meanwhile, interfacial Co─S bonds, together with the built‐in electric field, establish an S‐scheme charge‐transfer pathway that directs photoexcited electrons toward catalytically active sulfur sites. Consequently, the amorphous‐crystalline heterostructure achieves a photocatalytic H 2 evolution rate of 24.9 mmol g −1 h −1 under simulated solar light and produces ∼28 mL H 2 within 4 h under natural sunlight. These findings reveal amorphous‐crystalline interfaces as a versatile platform for coupling mechanical and electronic regulation in photocatalysis.