Fracture toughness of a metal-organic framework glass

T To and SS Sorensen and M Stepniewska and A Qiao and LR Jensen and M Bauchy and YZ Yue and MM Smedskjaer, NATURE COMMUNICATIONS, 11, 2593 (2020).

DOI: 10.1038/s41467-020-16382-7

Metal-organic framework glasses feature unique thermal, structural, and chemical properties compared to traditional metallic, organic, and oxide glasses. So far, there is a lack of knowledge of their mechanical properties, especially toughness and strength, owing to the challenge in preparing large bulk glass samples for mechanical testing. However, a recently developed melting method enables fabrication of large bulk glass samples (>25 mm(3)) from zeolitic imidazolate frameworks. Here, fracture toughness (K-Ic) of a representative glass, namely ZIF-62 glass (Zn(C3H3N2)(1.75)(C7H5N2)(0.25)), is measured using single-edge precracked beam method and simulated using reactive molecular dynamics. K-Ic is determined to be similar to 0.1MPa m(0.5), which is even lower than that of brittle oxide glasses due to the preferential breakage of the weak coordinative bonds (Zn-N). The glass is found to exhibit an anomalous brittle-to-ductile transition behavior, considering its low fracture surface energy despite similar Poisson's ratio to that of many ductile metallic and organic glasses.

Return to Publications page