Spontaneous assemblies of gigantic polyoxomolybdates; from structure and properties to synthetic methods

Gigantic polyoxomolybdates, dominated by the Molybdenum Blue (MB) family, constitute a key subclass of polyoxometalates (POMs) and play a fundamental role in elucidating structural construction principles and showcasing the diversity of POM architectures. Since the first structural determination of the iconic {Mo₁₅₄} big wheel cluster, these giant polyoxomolybdates have been developed rapidly over the past three decades, emerging as one of the most versatile classes of POM clusters. Potential applications span materials science, electronic materials, and catalysis. This tutorial review summarises the fundamentals of MBs and their close relatives including the highly reduced Mo browns and Mo reds, their molecular and electronic structures, physical properties, and synthetic methods for production. Drawing on 67 references from pivotal studies over the last thirty years, this review serves as both an authoritative reference for early-career researchers and an accessible introduction for non-professionals interested in this dynamic field.