Proton Alloying in an Organic-Inorganic Hybrid Material Enables Unusual Dynamic Birefringence and Martensitic...

Alloying is widely recognized as an effective strategy for enhancing or unlocking material properties by combining different elements. Organic-inorganic hybrid materials (OIHMs) allow for chemical modification at the molecular level, bringing new opportunities and enormous potential to alloying strategies. Hydrogen protons in molecules are essential for structural design and crystal engineering, however, valuable role of proton alloying in OIHMs remains largely unexplored. Herein, for the first time, we present a proton alloying OIHM [Cyclen⁴⁺Cyclen²⁺]Sb₂Cl₁₂ (Cyclen-1D), which exhibits exceptional martensitic actuation behaviors, including jumping, bending and a significant raising effect with a large expansion up to 50%. Meanwhile, Cyclen-1D also possesses unusual multi-mode dynamic birefringence featuring continuous modulation and switching mutation, showing an excellent birefringence change (Δn ≈ 0.044). This interesting integration of mechanical and optical channels originates from the asynchronous orientations of distinct protonated Cyclen cations as well as cooperative transformation with inorganic octahedron through hydrogen bonding. This work reveals the great potential of proton alloying in OIHMs, opening new avenues for designing dynamically stimuli-responsive materials.