TY - JOUR
T1 - Hydrolysis and condensation of ZIF-8 in water
AU - Zhang, Huifeng
AU - Zhao, Man
AU - Yang, Yang
AU - Lin, Y. S.
N1 - Funding Information:
The authors would like to acknowledge the financial support from National Key R&D project of China (No. 2017YFC0403901 ), National Natural Science Youth Foundation of China (No. 21606059 ), Marine Public Welfare Industry Research Project ( 201505006-3 ) and Special Fund for Basic Scientific Research Business of Central Public Research Institutes ( K-JBYWF 2016-T11/K-JBYWF-2017-T10 ). HF thank Dr. Dun-yen Kang at National Taiwan University for his kind help in providing structure data of ZIF(L) and dia(Zn).
Publisher Copyright:
© 2019
PY - 2019/11/1
Y1 - 2019/11/1
N2 - Recent studies have shown that zeolitic imidazolate framework-8 (ZIF-8) crystallites are not stable in aqueous solution under ambient conditions. When immersed in water, ZIF-8 crystallites are hydrolyzed to zinc and imidazolate ions, which can be condensed to form a new solid substance upon removal of water by evaporation. The present work demonstrates such ZIF-8 phase shift substance is of crystalline structure but does not belong to any known (pseudo)polymorphs of ZIF-8, ZIF-L, dia(Zn), or decomposed product of ZIF-8: Zn(OH)2 and 2-methylimidazole. FTIR characterization shows the co-existence of Zn–O and Zn–N bond in the new substance, confirming the partial cleavage of Zn–N bond in ZIF-8 building unit in the hydrolysis step. EDS quantification for the ZIF-8 phase shift substance gives a C:N:Zn:O atomic ratio of 40:20:5:4. Based on EDS and FTIR results, the chemical formula of Zn5(HMIM)4(MIM)6(OH)4 for the building unit of such substance is proposed consisting of four partially hydrolyzed and one undisturbed secondary ZIF-8 building units. The ZIF-8 phase shift substance is crystalline with a nearly identical atomic composition as ZIF-8 (except for increased oxygen content), suggesting it might be a novel pseudo-polymorph of ZIF-8. The hydrolysis and condensation of ZIF-8 can be described by a mechanism that includes (1) hydrolysis of ZIF-8 through cleavage of Zn–N bond to form zinc and imidazolate ions and partially hydrolyzed ZIF-8 units and (2) condensation of these ions and clusters with the help of hydrogen bond to form the new structure of ZIF-8 phase shift substance.
AB - Recent studies have shown that zeolitic imidazolate framework-8 (ZIF-8) crystallites are not stable in aqueous solution under ambient conditions. When immersed in water, ZIF-8 crystallites are hydrolyzed to zinc and imidazolate ions, which can be condensed to form a new solid substance upon removal of water by evaporation. The present work demonstrates such ZIF-8 phase shift substance is of crystalline structure but does not belong to any known (pseudo)polymorphs of ZIF-8, ZIF-L, dia(Zn), or decomposed product of ZIF-8: Zn(OH)2 and 2-methylimidazole. FTIR characterization shows the co-existence of Zn–O and Zn–N bond in the new substance, confirming the partial cleavage of Zn–N bond in ZIF-8 building unit in the hydrolysis step. EDS quantification for the ZIF-8 phase shift substance gives a C:N:Zn:O atomic ratio of 40:20:5:4. Based on EDS and FTIR results, the chemical formula of Zn5(HMIM)4(MIM)6(OH)4 for the building unit of such substance is proposed consisting of four partially hydrolyzed and one undisturbed secondary ZIF-8 building units. The ZIF-8 phase shift substance is crystalline with a nearly identical atomic composition as ZIF-8 (except for increased oxygen content), suggesting it might be a novel pseudo-polymorph of ZIF-8. The hydrolysis and condensation of ZIF-8 can be described by a mechanism that includes (1) hydrolysis of ZIF-8 through cleavage of Zn–N bond to form zinc and imidazolate ions and partially hydrolyzed ZIF-8 units and (2) condensation of these ions and clusters with the help of hydrogen bond to form the new structure of ZIF-8 phase shift substance.
KW - Hydrolysis mechanism
KW - Hydrostability
KW - ZIF-8
KW - Zeolitic imidazolate frameworks
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U2 - 10.1016/j.micromeso.2019.109568
DO - 10.1016/j.micromeso.2019.109568
M3 - Article
AN - SCOPUS:85068144836
SN - 1387-1811
VL - 288
JO - Microporous Materials
JF - Microporous Materials
M1 - 109568
ER -