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Density Functional Theory and the Quantum Chemistry of Gas Separation, Magnetism, and Catalysis in Metal–Organic Frameworks

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Density Functional Theory and the Quantum Chemistry of Gas Separation, Magnetism, and Catalysis in Metal–Organic Frameworks Density Functional Theory and the Quantum Chemistry of Gas Separation, Magnetism, and Catalysis in Metal–Organic Frameworks A DISSERTATION SUBMITTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY Pragya Verma IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Advisor: Prof. Donald G. Truhlar September, 2017 © Pragya Verma 2017 Acknowledgments This research was carried out under the guidance of Prof. Donald G. Truhlar. I thank him for his support, kindness, encouragement, great respect, and remarkable ability to find time in spite of being very busy whenever I have approached him to discuss anything. Don is extraordinary in many ways, and I had the great opportunity to interact with him and gain knowledge from him not just on scientific matters, but also non-scientific matters. During my PhD, I had the opportunity to interact with a number of Truhlar group members. In particular, I am grateful to Kaining Duanmu, Laura E. Fernandez, Xiao He, Shuping Huang, Sijie Luo, Kamal Sharkas, Zoltan Varga, Bo Wang, Xuefei Xu, Haoyu S. Yu, and Wenjing Zhang, for their contributions to various projects on which I have worked with them. My interactions with each one of them have been very fruitful, and I had the chance to learn numerous things from them that has enriched my knowledge in the field. I would also like to extend my gratitude to collaborators outside the Truhlar group, particularly the Gagliardi group. Members of Gagliardi group with whom I have interacted closely are Remi Maurice and Joshua Broycz, and I thank them for their useful insights in various projects. I want to thank the staff at Minnesota Supercomputing Institute (MSI) whom I have emailed quite often with my queries regarding MSI, and I have very often received a helpful response from them. Finally, this research would not have been successful without the generous financial help from various organizations and funding agencies. A major part of this research was supported by the U.S. Department of Energy (grant no. DE-FG02- 12ER16362), a Phillips 66 Excellence Fellowship, a Graduate School Doctoral Dissertation Fellowship, and the Richard D. Amelar & Arthur S. Lodge Fellowship. i Abstract This dissertation uses theoretical and computational methods, mainly the quantum mechanical density functional theory of electronic structure, to explore three functionalities of metal-organic frameworks (MOFs), namely, purification and separation of gaseous mixtures, catalysis of C–H bond activation, and potential use of MOFs as magnetic materials. The dissertation also includes the development and analysis of computationally efficient quantum mechanical and molecular mechanical methods that are more accurate than previously available methods. ii Table of Contents Acknowledgments .................................................................................... i Abstract .................................................................................................... ii List of figures .......................................................................................... vi List of tables........................................................................................... vii List of abbreviations and acronyms .................................................... xii 1 Introduction ...................................................................................... 1 1.1 Synopsis ......................................................................................................... 1 1.2 Metal–Organic Frameworks (MOFs) ............................................................ 1 1.3 Models............................................................................................................ 4 1.3.1 Cluster Models ....................................................................................... 4 1.3.2 Periodic Models ..................................................................................... 6 1.4 Method Development ..................................................................................... 7 1.5 Organization of the Thesis ............................................................................. 8 2 Gas Separation ................................................................................. 9 2.1 Synopsis ......................................................................................................... 9 2.2 Introduction .................................................................................................... 9 2.3 Methodology ................................................................................................ 11 2.4 Results and Discussion ................................................................................ 13 2.4.1 Hydrocarbon Separation ...................................................................... 13 2.4.2 O2/N2 Separation .................................................................................. 26 2.4.3 N2/CH4 Separation ............................................................................... 42 2.5 Concluding Remarks .................................................................................... 49 3 Catalysis .......................................................................................... 52 3.1 Synopsis ....................................................................................................... 52 3.2 Introduction .................................................................................................. 52 3.3 Methodology ................................................................................................ 56 3.4 Results and Discussion ................................................................................ 59 3.5 Concluding Remarks .................................................................................... 72 4 Magnetism ....................................................................................... 73 iii 4.1 Synopsis ....................................................................................................... 73 4.2 Introduction .................................................................................................. 73 4.3 Methodology ................................................................................................ 74 4.3.1 Quantum Mechanical Methods. ........................................................... 74 4.3.2 Spin Configurations ............................................................................. 76 4.4 Results and Discussion ................................................................................ 78 4.4.1 Isotropic Coupling Constants of Bare MOF ........................................ 79 4.4.2 Isotropic Coupling Constants of Physisorbed MOF ............................ 87 4.4.3 Isotropic Coupling Constants of Chemisorbed MOF ........................ 100 4.5 Concluding Remarks .................................................................................. 104 5 Density Functional Development ................................................ 106 5.1 Synopsis ..................................................................................................... 106 5.2 Introduction ................................................................................................ 107 5.3 Databases ................................................................................................... 110 5.4 The GAM Functional ................................................................................. 111 5.4.1 Functional Form ................................................................................. 111 5.4.2 Optimization of the Functional .......................................................... 114 5.4.3 Methodology ...................................................................................... 117 5.4.4 Functionals Used for Comparison ..................................................... 119 5.4.5 Results and Discussion ...................................................................... 120 5.5 DFT+U ....................................................................................................... 130 5.5.1 Methodology ...................................................................................... 131 5.5.2 Results and Discussion ...................................................................... 133 5.6 HLE functionals ......................................................................................... 149 5.6.1 Functional Form ................................................................................. 151 5.6.2 Methodology ...................................................................................... 151 5.6.3 Results and Discussion ...................................................................... 155 5.7 Concluding Remarks .................................................................................. 163 6 Molecular Mechanics Development ........................................... 166 6.1 Synopsis ..................................................................................................... 166 6.2 Introduction ................................................................................................ 166 6.3 Complexes Studied .................................................................................... 169 iv 6.4 Methodology .............................................................................................. 169 6.5 Results and Discussion .............................................................................
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