Computational Investigation of Nanoporous Materials for Clean Energy Applications

Nanoporous materials such as metal-organic frameworks (MOFs) are promising for applications in clean energy thanks to their diverse and extraordinary gas adsorption properties. Additionally, these materials' high degree of tunability means that nearly infinite distinct materials can be envisioned with different combinations of compositions, topologies, and surface properties. Each combination could yield a material with its own unique gas adsorption phenomena and resulting real-world applications. While many materials with outstanding properties have been studied, it remains a challenge to find or design an optimal material for a given application and to understand the complex molecular-level interactions that give rise to macroscopic behavior.In this dissertation, we take three different computational approaches towards advancing the discovery and understanding of nanoporous materials for various clean energy applications.In Chapters 2 and 3, we screen large databases of materials for carbon capture and hydrogen storage, using molecular simulations. We develop accurate atomistic models for the relevant adsorption phenomena and identify appropriate criteria for predicting performance. In this way, we identify optimal materials for carbon capture and hydrogen storage, as well as characteristics common among top performers. Ultimately, such findings can help guide the design of optimal materials for these applications.In Chapter 4, we study in depth a novel biporous MOF for natural gas processing, using molecular simulations in conjunction with experiments. This MOF's rare feature of biporosity, or coexistence of two chemically distinct pores within the same MOF, gives rise to unique stepwise activation that can be controlled to consequently tune the MOF's CO2/CH4 separation performance. This phenomenon is explained in terms of CO2's and CH4's differing interactions with the pore surfaces. In this way, we contribute to the understanding of complex behavior in biporous materials that affects their gas separation performance.Finally, in Chapter 5, we investigate the assembly process of MOFs using a statistical mechanical lattice model. In particular, we map out the thermodynamic assembly pathway of MOF-74 and explore the effect of surface tension energies on the shapes of nucleating clusters. With this study we work towards understanding the assembly pathway of MOFs with the ultimate goal of being able to control the synthesis process and obtain crystals of the desired morphology.