Photoexcited Anhydrous Proton Conductivity in Coordination Polymer Glass

Abstract

Optically switchable proton-conductive materials will enable the development of artificial ionic circuits. However, most switchable platforms rely on conformational changes in crystals to alter the connectivity of guest molecules. Guest dependency, low transmittance, and poor processability of polycrystalline materials hinder overall light responsiveness and contrast between on and off states. Here, we optically control anhydrous proton conductivity in a transparent coordination polymer (CP) glass. Photoexcitation of tris(bipyrazine)ruthenium(II) complex in CP glass causes reversible increases in proton conductivity by a factor of 181.9 and a decrease in activation energy barrier from 0.76 eV to 0.30 eV. Modulating light intensity and ambient temperature enables total control of anhydrous protonic conductivity. Spectroscopies and density functional theory studies reveal the relationship between the presence of proton deficiencies and the decreasing activation energy barrier for proton migrations.

Functional metal–organic liquids

“…Photoexcitation of the tris(bipyrazine)-ruthenium complex (Rubpz, 0.1 mol%) leads to improved responsiveness and intensifies the conductivity change between on and off states. 133–135 The system reaches the highest on/off ratio of over 180 times within 5 min, and the conductivity was controlled explicitly by continuously controlling the light intensity and ambient temperature. The metal-to-ligand charge transfer (MLCT) excitation of Rubpz initiates the p K a changes, where the proton is transferred from the ZnPIm glass domain to Rubpz, thus generating proton-deficient sites.…”

Ion transport and conduction in metal–organic framework glasses

“…Photo-responsive compounds such as pyranine and Ru-complex have been demonstrated to provide optically switchable proton conductivity in MOF glass, which is a promising start. 69,105 Other popular photo-responsive compounds such as azobenzenes and porphyrins can also be explored for a wider range of ions in future studies. 106,107 In addition, further possibilities exist to apply a photomask to achieve spatial control of the regions with low/high conductivities, which is worth exploring.…”

Organic–Inorganic Hybrid Glasses of Atomically Precise Nanoclusters

“…As a unique state of matter, glass has played a significant role in the rise of civilization and technology with its three traditional categories: inorganic, organic, and metallic glasses. − More recently, inorganic–organic hybrid glasses have emerged as a promising family of materials, attracting considerable research interest. − Hybrid glasses contain both inorganic and organic components that are typically connected via coordination bonds, resulting in diverse complementary advantages over their crystalline counterparts. For instance, metal–organic framework and coordination polymerspresently the main members of the hybrid glass familyexhibit multifunctional properties, such as gas permeability, thermoelectricity, luminescence, and ion conduction. − Glasses based on hybrid metal halides have also been demonstrated, displaying intriguing optical and thermoelectric properties. − Although inorganic–organic hybrid glasses have ignited a new field of material science, such glasses are typically susceptible to thermal decomposition or structural degradation more than their crystalline counterparts. − As a result, a reversible crystal–liquid–glass transition with good stability, which is a prerequisite for practical implementation, has rarely been achieved for these glasses. , Therefore, further exploration and extension of the glass family are still of significance for fundamental research and potential industrial application.…”