The integration of stimuli-responsive valence tautomeric (VT) molecular systems into solid materials without compromising their functionality is a major bottleneck for the use of these compounds in high-added value applications. In this work, an innovative, simple, and universal approach is described to tackle this challenge based on the confinement of the active species into liquid-filled polymeric capsules. A microstructured solid with optimized solution-like behavior is obtained in this way, whose VT properties can be rationally tuned upon variation of the encapsulated solvent. Incorporation of the resulting capsules into thin films or other matrices of interest allows successful transfer of valence tautomerism from the liquid phase to solid materials, thus paving the way to the fabrication of functional devices based on spin transition compounds.