Quartz‐Like Supramolecular Glass Enabled by Host–Guest Size Mismatch

Supramolecular glasses are conventionally restricted by a fundamental trade‐off between mechanical robustness and deep‐ultraviolet (UV) transparency, due to the ubiquitous reliance on aromatic building blocks. Herein, we overcome this limitation by reporting a “quartz‐like” supramolecular glass assembled from fully saturated aliphatic macrocycles and lithium salts, enabled by a host–guest size mismatch strategy. Crystallographic elucidation reveals that the undersized Li + guest induces severe conformational frustration within the macrocycle, which, in concert with weak anion coordination (PF 6 − ), kinetically suppresses crystallization. In contrast, size‐matched analogues (Na + /K + ) or strongly coordinating anions (Cl − /NO 3 − ) assemble as ordered crystalline solids. The resulting material resolves the traditional property conflict, exhibiting fused‐silica‐like transparency (>95%) spanning the deep‐UV to near‐infrared regions, while maintaining a high Young's modulus of ∼4.85 GPa, dynamic regenerative repair capability, and robust interfacial adhesion. Notably, the glass demonstrates exceptional stability against high‐intensity UV and γ ‐ray radiation. This study establishes mismatch‐induced frustration as a versatile conceptual framework for engineering optically silent supramolecular materials that decouple mechanical strength from optical bandgap.