Crystal melting and vitrification of nitrile-based two-dimensional coordination polymer (CP) were studied. The crystal melts at 169 °C and has a wide liquid-state temperature window of over 110 °C. The crystalline state transformed to a glassy state by melt-quench or mechanical milling. The mechanically induced glass showed permanent porosity, and it also showed glass-to-crystal transformation upon solvent treatment. Surface crystallization on top of the grain-boundary-free glass monolith was demonstrated.