Nucleation and growth studies of nanoporous materials using synchrotron and neutron radiation techniques

纳米多孔硅酸铝和磷酸铝是当代材料和催化化学中的关键体系，近几十年来合成了大量的微孔骨架材料。这些体系通常包含AlO4和SiO4或AlO4和PO4共享角四面体-形成整个组件的四面体，从而产生具有一定范围的孔尺寸的一维链状、二维层状或三维开放骨架结构。合成具有不同孔或笼尺寸和不同化学组成的新型微孔材料背后的主要推动力是设计引入特定形状选择和区域选择特性的新型催化系统。这些无机多相催化剂易于操作，可以回收，在许多情况下可以调整以产生最少量的副产品，并有可能用于大规模化学品生产。在这个项目中，我们打算进行一项详细的研究，以了解这些纳米孔系统的形成。我们将解决的关键问题是(1)成核物种是什么，(2)成核物种的结构是什么，它与最终结晶产物是否有任何相似之处，以及(3)在给定条件下特定结晶产物的形成所涉及的机制是什么。为了回答这些问题，有必要在运行(水热)条件下进行研究，并确定快速生长的结构，有必要使用时间分辨的高级表征技术。我们建议使用的技术是小角X射线散射法，以确定在成核过程的初始阶段形成的颗粒的大小和形状。同时，我们将使用广角X射线散射来监测结晶产物。为了确定在初始阶段形成的非晶态粒子的结构，我们将使用适用于非晶态固体的总散射法，特别是X射线和中子衍射法。从这些研究中获得的信息将提供关于结晶前网络形成机制的新信息，这些网络形成机制负责生产最终结晶产品。我们将使用先进的同步辐射和中子辐射源进行现场实验。通过了解这一过程，我们将能够制定策略来设计合成条件，以产生新的和新颖的纳米孔结构。

Nanoporous aluminosilicate and aluminophosphates are key systems in contemporary materials and catalytic chemistry, with a large number of synthetic microporous framework materials being documented over recent decades. These systems contain, in general, AlO4 and SiO4 or AlO4 and PO4 corner sharing-tetrahedra forming the entire assembly resulting in either one-dimensional chain, two-dimensional layered or three-dimensional open-framework structures with a range of pore dimensions. The main thrust behind the synthesis of new microporous materials, with different pore or cage dimensions and various chemical compositions, is to design novel catalytic systems that introduce specific shape selective and regio-selective properties. These inorganic heterogeneous catalysts are easy to handle, can be recycled and in many instances can be tuned to produce a minimum amount of side-products, and have the potential for use in the large-scale production of chemicals. In this project we propose to carry out a detailed study to understand the formation of these nanoporous systems. The key questions we will address are (1) what are the nucleating species, (2) what is the structure of the nucleating species and does it have any resemblance to the final crystalline product and (3) what is the mechanism involved in the formation of a specific crystalline product under a given conditions. To answer these questions it is necessary to carry out investigations under operating (hydrothermal) conditions and to determine structures that grows rapidly, it is necessary to use time-resolved advanced characterisation techniques. The techniques we propose to use are small-angle X-ray scattering method to determine the size and shape of the particles that are formed during the initial stages of the nucleation processes. Simultaneously we will monitor the crystallising product using wide-angle X-ray scattering. To determine the structure of the non-crystalline particles formed at the initial stages, we will use total scattering methods, in particular X-ray and neutron diffraction methods, applicable to amorphous solids. The information obtained from these studies will provide new information on the mechanism of the network formation prior to crystallisation, which are responsible for the production final crystalline product. We will use the advanced Synchrotron Radiation and Neutron Radiation sources to perform the in situ experiments. By understanding this process we will be able to develop strategy to design synthesis conditions to produce new and novel nanoporous structures.