Computational Techniques for Studying Nanoporous Materials

The central goal of this thesis has been the development of new computational techniques to accelerate the discovery and characterization of nanoporous materials. Chaper 1 introduces the field of nanoporous materials/reticular chemistry, provides a brief history of molecular simulation in reticular chemistry, and finally, discusses some key challenges that need to be addressed from a computational perspective. Chapter 2 introduces the objectives of this thesis including the organization of this thesis, and some of the important questions this thesis aims to answer. Chapter 3 begins with a detailed discussion on the theory behind GCMC simulations, including the partition function and the different moves in a GCMC simulation and their associated probabilities. Next, the chapter goes into detail of how the potential energy function *U* is calculated, i.e. force fields, including it’s two main contributing terms, (i) the bonded potential, *U_bonded*, and (ii) the nonbonded potential, *U_nonbonded*. Finally, the theory behind the calculation of different geometric properties like the accessible surface area, largest cavity diameter (LCD), and the pore limiting diameter (PLD) are discussed. Chapter 4 introduces our recent advances in HTS to rapidly screen *in silico* the adsorption properties of hundreds of MOFs for CO/N₂ separations. Our approach involves the use of a multi-scale toolbox combining high-throughput molecular simulations, data mining and advanced visualization, as well as process system modeling, backed up by experimental validation. Chapter 5 extends the high-throughput screening approach introduced in the previous chapter to rapidly screen the properties of not hundreds, but thousands of MOFs for H₂ storage. We also discuss how principal component analysis (PCA) can be used to extract meaningful insights from the vast amount of data generated from such screening studies. We validate our screening approach by synthesizing and evaluating the performance of the selected MOF (HKUST-1) in its monolithic form. Chapter 6 begins with an introduction to Small Angle X-ray Scattering (SAXS) and lattice gas models. Next, we introduce the concept of a monolith, and show experimentally the existence of interparticle mesopores - inaccessible from powders - that push final adsorption capacities above levels expected for single crystals. Finally, we show how lattice-gas models in combination with GCMC simulations can be used to accurately capture the monolithic structure across both the microporous and mesoporous range enabling the robust future predictions of the adsorption characteristics of monolithic materials. Chapter 7 begins with a derivation of the BET equation from first principles. We follow this up with a discussion on how the BET equation can be used to calculate the BET area, i.e. BET method, and some state-of-the-art problems with this method. Finally, we introduce an algorithmic approach called BETSI that addresses some of these problems. Chapter 8 summarizes the key results of this thesis and provides some context on the future outlook and challenges in this field.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2023

Author dc:creator

• Rampal, Nakul

Advisor dc:contributor.advisor

• Fairen-Jimenez, David

• Adsorption
• Molecular Simulation
• Nanoporous Materials

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/025477b9-a12b-4af7-9d4b-dfbe971fee8a/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.108035

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/367444