Towards stable metal inorganic-organic complex glasses

Abstract

Metal inorganic-organic complex (MIOC) glasses have emerged as a new family of melt-quenched glasses. However, the vitrification of MIOC is challenging since most of the crystalline MIOC precursors decompose before melting. The decomposition problem severely narrows the compositional range of MIOC glass formation. Here, we report a novel approach for preparing the MIOC glasses that combines slow-solvent-removal with subsequent quenching to avoid gel thermal decomposition and crystallization. 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 avoiding gel crystallization. Consequently, a disordered network is frozen-in during quenching of the dried gel from 130 °C to room temperature, and finally MIOC glass forms. Structural analyses reveal that hydrogen bonds are responsible for connecting the tetrahedral units. The as-prepared MIOC glass exhibits some fascinating behaviors, e.g., Tg increasing with rapid room-temperature relaxation, CO2 uptake, and red-shift of photoluminescence. This work not only presents a novel strategy for fabricating large-sized, stable, functional MIOC glasses, but also uncovers the critical role of hydrogen bonds in MIOC glass formation.