Towards stable metal organic-inorganic complex glasses

Abstract

Metal organic-inorganic complex (MOIC) glasses have emerged as a new family of hybrid glasses. However, the low thermal stability of MOIC glasses fabricated via crystallization suppression constrains their practical applicability under ambient conditions. Here, we report a novel approach for preparing the MOIC glasses that combines slow-solvent removal with subsequent quenching to avoid gel thermal decomposition and enhance the thermal stability of the obtained glass. Specifically, the new approach utilizes an aprotic solvent (acetone) to kinetically prevent the ordering of the metal-ligand complex molecules in solution, thereby suppressing crystallization and forming a gel. The subsequent gradual drying process leads to the removal of the solvent to enhance the connections between molecules through hydrogen bonds, thus causing the formation of a hydrogen-bonded network. The increased network connectivity lowers the mobility of the molecules, thereby enhancing the thermal stability of the system. A disordered network of dried gel is frozen-in via cooling from 130 °C to room temperature, and hence, MOIC glass forms. Structural analyses reveal that hydrogen bonds are responsible for connecting the tetrahedral units. The as-prepared MOIC glass exhibits an increase in glass transition temperature (T_g) during rapid room-temperature relaxation, enhanced CO₂ uptake, and a red shift in photoluminescence. This work not only presents a novel strategy for fabricating large-sized, stable, functional MOIC glasses but also uncovers the critical role of hydrogen bonds in MOIC glass formation.