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 (Tg), 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.