Metal-Organic Crystallized Glasses: Microstructure Formation and Their Properties

Partial crystallization within a glass matrix to form microcrystalline domains offers a pathway to glass-ceramic materials with properties distinct from those of both the parent glass and crystalline phases. This concept has been limited to inorganic glasses. Here, we introduce metal-organic crystallized glasses (MOCGs), prepared by controlling the crystallization process within metal-organic framework (MOF) glasses, and explore their properties. By adjusting the annealing temperature and duration above the glass transition temperature (T_g), we control the crystallinity and crystallite size in 2D Cd(H₂PO₄)₂(1,2,4-triazole)₂-based MOCGs, enabling modulation of their micromechanical properties, dielectric constants, and proton conductivities. The MOCG with a 15% relative crystallinity exhibits a dielectric constant of 3.3 × 10² at 100 kHz, an order of magnitude higher than that of both the parent glass and crystalline phases across 30-100 °C. We further extend this concept to a mixed-metal MOF glass system, where solid solutions occur through the incorporation of Cd²⁺ and Mn²⁺ ions from the amorphous matrix into crystallizing lattices upon annealing.