COMPUTATIONAL STUDY OF ADSORPTION AND DIFFUSION IN METAL-ORGANIC FRAMEWORKS BABARAO RAVICHANDAR (M.Tech., NIT, India) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMICAL AND BIOMOLECULAR ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2009 Acknowledgement First of all, I would like to extend my sincerest and deepest gratitude to my supervisor Prof Jiang Jianwen His constant help, stimulating suggestions and encouragement from the initial to the final stage have enabled me to develop a good understanding of the subject His enthusiasm, positive outlook and belief in my abilities have helped me go through the difficult phases of research I would like to extend my thanks to all the members in Prof Jiang’s research group for their invaluable suggestions, discussions and sharing of technical expertise since the beginning of my PhD study I also wish to thank Dr Shaji Chempath for his help during the initial phase of research My special appreciation is due to Prof Stanley I Sandler from the University of Delaware for his comments and suggestions on my research papers I would also like to convey my thanks to Prof Mario S C Mazzoni for kindly providing the structure of covalent-organic framework nanotube My appreciations are due to Prof Mohamed Eddaoudi and Prof Yunling Liu for their helpful discussions on the crystallographic structure of zeolite-like metal-organic frameworks I would also like to express my sincere thanks to National University of Singapore for providing me the research scholarship Finally, I am deeply indebted to my parents and my wife for their love, support and encouragement during my PhD study i TABLE OF CONTENTS ACKNOWLEDGEMENT…………………………………………………… i TABLE OF CONTENTS…………………………………………………… ii SUMMARY……………………………………………………………… vii NOMENCLATURES………………………………………………………….x LIST OF FIGURES……………………………………………………… xv LIST OF TABLES……………………………………………………… xxiii CHAPTER INTRODUCTION …………………………………………… 1.1 Development of Metal-Organic Frameworks ……………………………1 1.2 Industrial Applications ………………………………………………… 12 1.2.1 Gas Storage …………………………………………………… 13 1.2.2 Gas Separation ………………………………………………… 18 1.2.3 Catalysis ……… ……………………………………………… 21 1.3 Scope of the Thesis …………………………………………………… 22 1.4 Organization of the Thesis …………………………………………… 24 CHAPTER LITERATURE REVIEW ……………………………… 25 2.1 Single-Component Adsorption ……………………………………… 25 2.1.1 H2 Storage …………………………………………………… 25 2.1.2 CH4 Storage…………………………………………………… 31 2.1.3 CO2 Storage…………………………………………………… 32 2.1.4 Other Gases…………………………………………………… 33 2.2 Multi-Component Adsorption ………………………………………… 35 2.3 Diffusion ……………………………………………………………… 38 ii CHAPTER SIMULATION METHODOLOGY……………………… 41 3.1 Interaction Potential …………………………………………………… 41 3.2 Monte Carlo …………………………………………………………… 43 3.2.1 3.2.2 Grand Canonical Ensemble…………………………………… 45 3.2.3 3.3 Canonical Ensemble…………………………………………… 43 Gibbs Ensemble ……………………………………………… 47 Molecular Dynamics ……………………………………………… … 49 CHAPTER ADSORPTION AND DIFFUSION OF CO2 AND CH4 IN DIFFERENT TYPES OF NANOPOROUS MATERIALS…………… 52 4.1 Introduction …………………………………………………………… 52 4.2 Models………………………………………………………………… 54 4.3 Methodology…………………………………………………………… 60 4.4 Results and Discussion ……………………………………………… 64 4.4.1 Adsorption of Pure and Binary Components………………… 64 4.4.1.1 4.4.1.2 Adsorption Isotherms ……………………………… 65 4.4.1.3 Isosteric Heats of Adsorption……………………… 68 4.4.1.4 4.4.2 Limiting Properties ………………………………… 64 Adsorption Isotherms of Binary Components……… 71 Diffusion of Pure Components………………………………… 74 4.4.2.1 4.4.2.2 Self-diffusivities …………………………………… 76 4.4.2.3 Corrected-diffusivities ……………………………… 78 4.4.2.4 Transport-diffusivities ……………………………… 80 4.4.2.5 4.4.3 Diffusivities at Infinite Dilution………………………74 Correlation Effects ………………………………… 82 Diffusion of Binary Components……………………………… 86 4.4.3.1 4.4.4 4.5 Self-diffusivities…………………………………… 86 Permselectivity………………………………………………… 89 Summary……………………………………………………………… 91 iii CHAPTER STORAGE OF CO2 IN METAL-ORGANIC AND COVALENT-ORGANIC FRAMEWORKS……………………………… 94 5.1 Introduction…………………………………………………………… 94 5.2 Models………………………………………………………………… 5.3 Methodology…………………………………………………………… 104 5.4 Results and Discussion………………………………………………… 108 5.4.1 95 Adsorption in MFI, SWNT and MOFs………………………… 108 5.4.1.1 5.4.1.2 Adsorption Capacities and Isosteric Heat…………… 110 5.4.1.3 Effect of Cations …………………………………… 114 5.4.1.4 5.4.2 Structural and Limiting Properties………………… 108 Adsorption Capacity in MOFs ……………………… 115 Adsorption in COFs…………………………………………… 118 5.4.2.1 5.5 118 5.4.2.2 5.4.3 Structural and Limiting Properties………………… Adsorption Isotherms in COFs…………………… 119 Quantitative Assessment of CO2 Storage in MOFs and COFs… 121 Summary……………………………………………………………… 123 CHAPTER ADSORPTION SEPERATION OF CO2/CH4 MIXTURES IN METAL-ORGANIC FRAMEWORKS WITH UNIQUE CHARACTERISTICS…………………………………………………… 126 6.1 Introduction…………………………………………………………… 126 6.2 Models ………………………………………………………………… 127 6.3 Methodology…………………………………………………………… 130 6.4 Results and Discussion………………………………………………… 131 6.4.1 6.4.2 Adsorption Selectivity ………………………………………… 134 6.4.3 Effect of Electrostatic Interactions on Adsorption Selectivity… 136 6.4.4 6.5 Adsorption Isotherms………………………………………… 131 Adsorption Isotherm and Selectivity in Charged MOF… 138 Summary……………………………………………………………… 139 iv CHAPTER SEPARATION OF GAS MIXTURES IN ZEOLITE-LIKE METAL-ORGANIC FRAMEWORK……………………………………… 142 7.1 Introduction…………………………………………………………… 142 7.2 Models ………………………………………………………………… 145 7.3 Methodology ………………………………………………………… 148 7.4 Results and Discussion………………………………………………… 151 7.4.1 7.4.2 Pure Gas……………………………………………………… 154 7.4.3 CO2/H2 Mixture………………………………………………… 155 7.4.4 CO2/N2 Mixture………………………………………………… 158 7.4.5 7.5 Characterization of Na+ Ions ………………………………… 151 CO2/CH4 Mixture and Effect of H2O ………………………… 159 Summary……………………………………………………………… 164 CHAPTER ADSORPTION AND DIFFUSION OF ALKANE ISOMER MIXTURES IN METAL-ORGANIC FRAMEWORKS…… 166 8.1 Introduction…………………………………………………………… 166 8.2 Models ………………………………………………………………… 168 8.3 Methodology ………………………………………………………… 171 8.4 Results and Discussion………………………………………………… 174 8.4.1 8.4.2 Adsorption Selectivity………………………………………… 179 8.4.3 8.5 Adsorption …………………………………………………… 174 Diffusion ……………………………………………………… 182 Summary ……………………………………………………………… 186 CHAPTER DRUG IN MESOPOROUS METAL ORGANIC FRAMEWORK MIL-101……………………………………………………… 188 9.1 Introduction…………………………………………………………… 188 9.2 Models ………………………………………………………………… 190 9.3 Methodology ………………………………………………………… 193 9.4 Results and Discussion………………………………………………… 194 v 9.4.1 9.4.2 9.5 Maximum Loading and Lowest Energy Conformation……… 194 Mobility of Ibuprofen ………………………………………… 198 Summary……………………………………………………………… 199 CHAPTER 10 CONCLUSIONS AND FUTURE WORK……………… 201 10.1 Conclusions …………………………………………………………… 201 10.2 Future Work…………………………………………………………… 207 REFERENCES……………………………………………………………… 209 PUBLICATIONS ………………………………………………………… 238 PRESENTATIONS ………………………………………………………… 239 APPENDIX A ……………………………………………………………… 240 vi Summary Adsorption and diffusion in nanoporous materials lie at the heart of many largescale industrial applications such as gas separation, storage and selective catalysis As the number of nanoporous materials to date is extremely large, selecting a promising material from discovery to applications is a challenge The development of particular technological applications for nanoporous materials requires the fundamental understanding of their microscopic properties In this sense, computational study plays an important complementary role to experiments by making predictions prior to experimental studies The selection of a suitable adsorbent is a key step in the design of adsorption-based storage or separation processes While most studies have focused on zeolites and carbon-based adsorbents, a new class of hybrid materials has been recently developed, i.e metal-organic frameworks (MOFs) which consist of metaloxide clusters and organic linkers MOFs allow the formation of tunable porous frameworks with a wide variety of architectures, topologies and pore sizes Because of their high porosity and well-defined pore size, MOFs are promising candidates for the storage and separation of gases, ion-exchanges, catalysis, sensing, etc In this thesis, molecular simulation techniques such as Monte Carlo and molecular dynamics have been used to elucidate the adsorption and diffusion phenomena of fluids in a wide variety of MOFs (1) The adsorption and diffusion of CO2 and CH4 were examined in three different nanoporous materials (silicalite, C168 schwarzite, and IRMOF-1) IRMOF-1 has a significantly higher adsorption capacity for CO2 and CH4 than silicalite and C168 schwarzite, however the adsorption selectivity of CO2 over CH4 was found to be similar in all the three adsorbents The permselectivity was calculated based on the adsorption and diffusion selectivity of the mixture, and found to be marginal in vii IRMOF-1, slightly enhanced in MFI, and greatest in C168 schwarzite Although IRMOF-1 has the largest storage capacity for CH4 and CO2, its selectivity is not satisfactory (2) CO2 storage in a series of MOFs was studied with different characteristics In addition, covalent-organic frameworks (COFs), a sub-set of MOFs were also considered Organic linker was revealed to play a critical role in tuning the free volume and accessible surface area, and subsequently determines CO2 adsorption at high pressures Due to low framework density and high porosity, COF-105 and COF108 exhibit the highest storage capacity among the adsorbents studied and even surpass the experimentally reported highest capacity in MOF-177 COF-102 and COF-103 are promising materials with high capacity at low pressures The gravimetric and volumetric capacity of CO2 at a moderate pressure correlates well with the framework density, free volume, porosity and accessible surface area of both MOFs and COFs These correlations are useful for a priori prediction of CO2 capacity and for the rational screening of MOFs and COFs toward high-performance CO2 storage (3) The adsorption and separation of CO2/CH4 mixture were studied in a series of metal-organic frameworks (MOFs) with unique characteristics such as exposed metals (Cu-BTC, PCN-6 and PCN-6), catenation (IRMOF-13 and PCN-6) and extraframework ions (soc-MOF) The framework catenation leads to constricted pores and additional adsorption sites, and enhances the interaction with the adsorbate Therefore, catenated IRMOF-13 and PCN-6 exhibit a greater extent of adsorption, particularly for CO2 at low pressures compared to IRMOF-14 and PCN-6; however, the opposite was observed to be true at high pressures It was found that catenated MOFs have a higher selectivity than their non-catenated counterparts Much higher viii selectivity is observed in charged soc-MOF compared with other IRMOFs and PCN structures For the first time, the extra-framework ions were characterized and gas separation was examined in a charged MOF, rho-ZMOF, with anionic framework In rhoZMOF, the presence of highly ionic framework enhances the CO2 capacity at low pressure and in turn increases adsorption selectivity The selectivity was ~ 1800 for CO2/H2, 80 for CO2/CH4, and 500 for CO2/N2 mixtures Compared with other MOFs and nanoporous materials reported to date, rho-ZMOF exhibits unprecedentedly high selective adsorption for gas mixtures (4) The effect of catenation on the separation of alkane isomers mixture was simulated Competitive adsorption between isomers was observed, particularly at high pressures, in which a linear isomer shows a larger extent of adsorption due to configurational entropy It was found that both adsorption and diffusion selectivities can be enhanced by catenation, particularly at low pressures (5) The microscopic properties of a model drug, ibuprofen, were studied in mesoporous MIL-101 and UMCM-1 based on molecular simulation and 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R., Jiang, JW Upgrade of Natural Gas in rho Zeolite-like Metal-Organic Framework and Effect of Water: A Computational Study, 2009, Energy and Environmental Science, 2, 1088-1093 (Selected as Cover Art) Babarao, R., Jiang, JW Unprecedentedly High Selective Adsorption of Gas Mixtures in a Zeolite-like Metal-Organic Framework: A Molecular Simulation Study, Journal of the American Chemical Society, 2009, 131, 11417-11425 Babarao, R., Jiang, JW., Sandler, SI Adsorptive Separation of CO2/CH4 Mixture in Metal Exposed, Catenated and Charged Metal-Organic Frameworks: Insight from Molecular Simulation, Langmuir, 2009, 25, 5239-5247 (Selected as Cover Art) Babarao, R., Tong, YH., Jiang, JW Molecular Insight into Adsorption and Diffusion of Alkane Isomer Mixtures in Metal-Organic Frameworks, Journal of Physical Chemistry B, 2009, 113, 9129-9136 Babarao, R., Jiang, JW Exceptionally High CO2 storage in Covalent-Organic Frameworks: Atomistic Simulation Study, Energy and Environmental Science, 2008, 1,139-143 Babarao, R., Jiang, JW Molecular Screening of Metal-Organic Frameworks for CO2 Storage, Langmuir, 2008, 24, 6270-6278 Babarao, R., Jiang, JW Diffusion and Separation of CO2 and CH4 in Silicalite, C168 schwarzite, and IRMOF-1: A Comparative Study from Molecular Dynamics Simulation, Langmuir, 2008, 24, 5474-5484 Babarao, R., Hu, ZQ., Jiang, JW., Chempath, S., Sandler, SI Storage and Separation of CO2 and CH4 in Silicalite, C168 schwarzite, and IRMOF-1: A Comparative Study from Monte Carlo Simulation, Langmuir, 2007, 23, 659-666 (Most Cited Article in Langmuir 2007) 238 PRESENTATIONS Charged Metal-Organic Framework for Highly Selective Adsorption of Gas Mixtures: A Molecular Simulation Study, Babarao, R., Jiang, JW 5th Pacific Basin Conference on Adsorption Science and Technology, May 25-27, 2009, Singapore Storage of CO2 in Hybrid Open Frameworks: A Computational Study, Babarao, R., Jiang, JW International Conference on Environment, Dec 15-17, 2008, Penang, Malaysia Metal-Organic Framework for CO2 storage and CO2/CH4 Separation, Babarao, R., Jiang, JW (2008), AIChE Annual Meeting, Nov 16-21, 2008, Philadelphia, USA Exploring the Distribution and Mobility of Nonframework ions in Charged MetalOrganic Frameworks Using Atomistic Simulations, Babarao, R., Nalaparaju, A., Jiang, JW AIChE Annual Meeting, Nov 16-21, 2008, Philadelphia, USA Adsorption and Diffusion of H2 in Metal-Organic Frameworks: Atomistic Simulation Study, Babarao, R., Chen, Y., Jiang, JW Asian Conference on Nanoscience and Nanotechnology (AsiaNano), Nov 3-7, 2008, Singapore Molecular Screening of Metal-Organic Frameworks for CO2 Storage, Babarao, R., Jiang, JW International Congress on Membrane and Membrane Processes, July 1218, 2008, Hawaii, USA Atomistic Simulation for Adsorption and Separation of CH4 and CO2 in Silicalite, C168 schwarzite and IRMOF-1, Babarao, R., Jiang, JW 13th Regional Symposium on Chemical Engineering, Nanyang Technological University, Oct 3-5, 2007, Singapore A Comparative Study on Separation of CO2/CH4 in Nanoporous Materials from Atomistic Simulation, Babarao, R., Jiang, JW 4th Annual Graduate Student Symposium, National University of Singapore, Singapore, Sep 22nd, 2008 (Best Poster Award) 239 APPENDIX A COPYRIGHT CLEARANCE 240 ... linkers in various MOFs (IRMOF-1, IRMOF-3, IRMOF-1-4NH2, IRMOF-6, IRMOF-8, IRMOF-12, IRMOF-14, IRMOF-18 and IRMOF-993) and found that the larger linkers bind more H2 molecules and addition of. .. predicted in catenated and non-catenated MOFs  To study the adsorption and diffusion of a model drug (ibuprofen) in mesoporous MIL-101 and UMCM-1 The energetics and dynamics of ibuprofen in the MOFs... (left) and volumetric (right) isotherms of CO2 116 adsorption in IRMOF1, Mg-IRMOF1, Be-IRMOF1, IRMOF1 (NH2)4, IRMOF10, IRMOF13, IRMOF14, UMCM-1, F-MOF1 and COF102 Figure 5.9 Gravimetric (left) and