Multiscale studies of framework structure, composition and defect influences on small molecule behaviour in zeolites

沸石是一种微孔硅基固体，具有高度可修饰的结构。它们的主要特征是含有分子大小的孔隙。这一特性使其在催化（化石燃料工业中碳氢化合物的裂解和转化）、分子筛分和水净化等一系列应用中得到广泛应用。它们在药物输送系统和农用化学工业中也有进一步应用的潜力。所有这些过程都需要小分子进入沸石骨架，通过孔系统扩散到活性位点，在那里它可以发生反应，并最终扩散出系统。这意味着分子在沸石结构内的运动是非常有趣的，因为它可以定义它们的用途。它还可以指导哪些合成后处理可以应用于沸石，以优化其结构，组成和后续应用。影响分子筛分子行为的最重要因素之一是分子筛与结构特征和缺陷（如阳离子、Bronsted酸位、硅烷醇巢和框架外铝）的相互作用。目前，在准确了解这些特性对沸石工业应用的影响方面存在很大的研究空白。研究问题：本研究旨在量化和理解结构特征对沸石内小分子扩散在多个尺度上的影响，这意味着实验和理论技术都将被采用。不同结构类型（即孔径和几何形状的变化）、结构特征（即不同的反离子、硅醇巢、酸位）和成分（即硅铝比）的大量组合需要进行研究，并在许多不同的组合中充分了解这些变量的影响以及它们如何相互作用。目的：测量结构特征和缺陷对小分子（如水、短链烃、氨）扩散率的影响。最初，从沸石中含有布朗斯特德酸位点和硅烷醇巢缺陷的水开始。测定不同阳离子（如钠、钾、钙）掺入沸石的效果。研究框架拓扑结构如何与其他因素一起改变分子行为。最初从工业相关的结构类型开始，如ZSM-5和FAU (Zeolite Y)，但有可能进一步发展。通过基于密度泛函理论的量子力学计算以及振动光谱等实验技术对这些系统进行计算建模，以研究分子尺度的行为。通过经典分子动力学模拟和准弹性中子散射实验来研究纳米尺度的行为。总之，多尺度、多面性的方法将允许产生新的想法和见解，以了解小分子在具有不同成分和缺陷的沸石中的限制行为。有很多原因可以解释为什么这项研究适合获得EPSRC的资助。首先，该项目的基本性质，来自“自下而上”的方法，使英国在研究方面具有全球竞争力。最重要的是，这项研究的性质为沸石科学的理解提供了长期的影响。最后，由于这些材料广泛的工业应用，特别是催化，它对工业和经济的影响。EPSRC相关研究领域：计算与理论化学、催化、化石燃料发电

Zeolites are microporous silica-based solids with a highly modifiable structure. Their defining characteristic is that they contain pores of molecular dimensions. This feature has led to their widespread use in a range of applications such as catalysis (in the cracking and transformation of hydrocarbons in the fossil fuel industry), molecular sieving and water purification. They also have potential for further use in drug delivery systems and the agrochemical industry. All these processes require small molecules to enter the zeolite framework, diffuse through the pore system to an active site, where it can undergo a reaction, and to eventually diffuse out of the system. This means that the movement of molecules confined within the zeolite structure is of great interest as it can define their use. It can also guide which post-synthetic treatments may be applied to the zeolite to optimise its structure, and composition, and subsequent application. One of the most important factors affecting molecular behaviour within zeolites are the interactions with structural features and defects (such as cations, Bronsted acid sites, silanol nests and extra-framework aluminium). Currently, there is a significant research gap in gaining an accurate understanding of the effect of these features which will have high impact on the industrial applications of zeolites.Research question: This research aims to quantify and understand the effects of structural features on small molecule diffusion within zeolites on multiple scales - meaning that both experimental and theoretical techniques will be employed. A large combination of different structure types (i.e. variations in pore size and geometry), structural features (i.e. different counter ions, silanol nests, acid sites) and compositions (i.e. silicon to aluminium ratios) need to be investigated and in many different combinations to fully understand the effects of these variables and how they can interplay with each other.Objectives:Measure the effect structural features and defects on the diffusivity of small molecules (such as water, short chain hydrocarbons, ammonia). Initially, starting with water in zeolites containing Bronsted acid sites and silanol nest defects. Determine the effect of different cations (such as sodium, potassium, calcium) being incorporated in the zeolites.Investigate how framework topology, alongside other factors, can alter the molecular behaviour. Initially starting with industrially relevant structure types - such as ZSM-5 and FAU (Zeolite Y) - but with the potential to move further afield.Model these systems computationally via quantum mechanical calculations based on density functional theory alongside experimental techniques such as vibrational spectroscopy to investigate the molecular-scale behaviour. Investigate the nanoscale behaviour via simulation with classical molecular dynamics paired with quasielastic neutron scattering experiments. Together, the multiscale-multifaceted approach will allow the production of novel ideas and insights into how small molecules behave upon confinement within zeolites with varied compositions and defects present. There are multiple reasons why this research is appropriate for funding from the EPSRC. Firstly, the fundamental nature of the project, coming from a "bottom-up" approach keeps the UK globally competitive in research. On top of this, the nature of the study provides a long-term impact in terms of the understanding within zeolite science. And finally, it's impact on industry and therefore the economy due to the wide-ranging industrial applications - particularly catalysis - of these materials.Relevant EPSRC research areas:Computational and theoretical chemistryCatalysisFossil Fuel power generation