Schematic illustration of nucleation-growth mechanisms in Prussian blue analogues (PBAs) synthesis and their temperature-dependent crystallization control. (A) PBA’s nucleation and growth kinetics are largely governed by temperature, where T_f and T_m1/T_m2 represent the solidification temperature (addition EG) and the fastest rate of nucleation/growth temperature of the precursor solution. (B) The scenarios of PBA synthesis under different temperatures. Conventional synthesis routes exhibit limited control over particle size distribution due to rapid nucleation under ambient conditions. Thermodynamically favored growth leads to particle aggregation with heterogeneous size distribution at room temperature (upper panel). The sub-zero synthesis cannot be achieved due to the freezing of the aqueous precursor solution (middle panel). Our developed cryo-synthesis approach introduces hydrogen-bond disrupting additives, achieving monodisperse nanocrystals with enhanced crystallinity (lower panel).