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Metal organic frameworks (MOF) are pioneering extremely porous materials that have been widely studied for applications such as gas storage, gas separation,

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Presentation on theme: "Metal organic frameworks (MOF) are pioneering extremely porous materials that have been widely studied for applications such as gas storage, gas separation,"— Presentation transcript:

1 Metal organic frameworks (MOF) are pioneering extremely porous materials that have been widely studied for applications such as gas storage, gas separation, heterogeneous catalysis, and sensing. To date there have been no experimental thermodynamic studies on their stability. James Hughes, Ph.D. student in the Peter A. Rock Thermochemisty Laboratory has completed the first ever thermodynamic measurement of a MOF material. The enthalpy of formation of “as-made” MOF-5 with respect to dense states, zinc oxide, terephthalic acid (H 2 BDC) and diethyl formamide (DEF) is 36.2 ± 1.3 kJ per mole of zinc atoms. Thus MOF-5, though it can be formed from solution, is metastable relative to zinc oxide and neat organic precursors, reflecting its porosity. Despite the difference in chemistry, the enthalpy of formation of MOF-5 falls on the same trend versus molar volume as the zeolitic and mesoporous silica materials. This suggests a rich energy landscape, with many different structures having similar energetics for MOF materials. First ever heat of formation measurement for a metal organic framework (MOF) shows energetics on same trend as zeolites and mesoporous silicas Alexandra Navrotsky, University of California at Davis, DMR Navrotsky, A., O. Trofymluk, A. Levchenko (2009). "Thermochemistry of Microporous and Mesoporous Materials." Chemical Reviews 109(9): MOF enthalpy of formation with respect to dense state in comparison with the energetics of zeolitic, mesoporous, and dense SiO 2 polymorphs 1. Volume and enthalpy of MOF-5 is per mole of Zn, that of silica phases is per mole Si. 4ZnO + 3H 2 BDC + 6.7DEF + (36.2 ± 1.3) kJ → Zn 4 O(BDC) 3 ∙6.7DEF + 3H 2 O

2 Porous materials have always attracted the interest of industry seeking ways to improve industrial processes. Zeolites have been used in numerous applications for over 50 years. However, limited pore size and high cost of manufacturing “large mouthed” zeolites have been a major impedance for expansion to new applications. Mesoporous materials, which appeared in the early 1990s, have on average 2 -3 times the pore space as zeolites but amorphous portions of their structure limits their durability and use for processes not already fulfilled by crystalline zeolites. MOFs on the other hand can withstand relatively extreme conditions while maintaining their porous structure. This trait has driven the interest into searching for applications of MOF materials. Thermodynamic studies undertaken by this laboratory will aid in the understanding where MOF fall within the energetic landscape. Assisting in improving synthesis conditions and the engineering of new MOFs. The graph above displays prominent, highly porous zeolites, mesoporous and MOF materials at the time off their discovery over the last four decades. The porosity of zeolites and mesoporous materials are in terms of volume per mole of Si atom, MOFs is volume per mole of metal atoms. The dramatic jump in pore space stems form the ability to swap organic linker molecules that bridge metal oxide clusters. This affords a unique opportunity to design and engineer frameworks with predefined pore volumes and allow the pore space to be chemically altered in ways previously not possible. The first ever metal organic framework (MOF) heat of formation measurement Alexandra Navrotsky, University of California at Davis, DMR


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