TY - JOUR
T1 - A metal-organic framework with ultrahigh glass-forming ability
AU - Qiao, A.
AU - Bennett, T.D.
AU - Tao, H.Z.
AU - Krajnc, A.
AU - Mali, G.
AU - Doherty, C.M.
AU - Thornton, A.W.
AU - Mauro, J.C.
AU - Greaves, G.N.
AU - Yue, Yuanzheng
PY - 2018
Y1 - 2018
N2 - Glass-forming ability (GFA) is the ability of a liquid to avoid crystallization during cooling. Metal-organic frameworks (MOFs) are a new class of glass formers (1-3), with hitherto unknown dynamic and thermodynamic properties. We report the discovery of a new series of tetrahedral glass systems, zeolitic imidazolate framework-62 (ZIF-62) [Zn(Im
2-xbIm
x)], which have ultrahigh GFA, superior to any other known glass formers. This ultrahigh GFA is evidenced by a high viscosity h (10
5 Pa·s) at the melting temperature T
m, a large crystal-glass network density deficit (δP/P
g)network, no crystallization in supercooled region on laboratory time scales, a low fragility (m = 23), an extremely high Poisson's ratio (v = 0.45), and the highest T
g/T
m ratio (0.84) ever reported. T
m and T
g both increase with benzimidazolate (bIm) content but retain the same ultrahigh T
g/T
m ratio, owing to high steric hindrance and frustrated network dynamics and also to the unusually low enthalpy and entropy typical of the soft and flexible nature of MOFs. On the basis of these versatile properties, we explain the exceptional GFA of the ZIF-62 system.
AB - Glass-forming ability (GFA) is the ability of a liquid to avoid crystallization during cooling. Metal-organic frameworks (MOFs) are a new class of glass formers (1-3), with hitherto unknown dynamic and thermodynamic properties. We report the discovery of a new series of tetrahedral glass systems, zeolitic imidazolate framework-62 (ZIF-62) [Zn(Im
2-xbIm
x)], which have ultrahigh GFA, superior to any other known glass formers. This ultrahigh GFA is evidenced by a high viscosity h (10
5 Pa·s) at the melting temperature T
m, a large crystal-glass network density deficit (δP/P
g)network, no crystallization in supercooled region on laboratory time scales, a low fragility (m = 23), an extremely high Poisson's ratio (v = 0.45), and the highest T
g/T
m ratio (0.84) ever reported. T
m and T
g both increase with benzimidazolate (bIm) content but retain the same ultrahigh T
g/T
m ratio, owing to high steric hindrance and frustrated network dynamics and also to the unusually low enthalpy and entropy typical of the soft and flexible nature of MOFs. On the basis of these versatile properties, we explain the exceptional GFA of the ZIF-62 system.
UR - http://www.scopus.com/inward/record.url?scp=85044104649&partnerID=8YFLogxK
U2 - 10.1126/sciadv.aao6827
DO - 10.1126/sciadv.aao6827
M3 - Journal article
C2 - 29536040
SN - 2375-2548
VL - 4
SP - eaao6827
JO - Science Advances
JF - Science Advances
IS - 3
M1 - eaao6827
ER -