多级孔材料研究进展

多孔材料具有孔隙率高、比表面积大、导热系数低、体积密度小及化学性质稳定等优点,在吸附与分离、催化剂载体、隔热材料、能量储存、传感器等领域拥有广阔的应用前景。基于孔直径的大小可将多孔材料分为三类:孔径大于50nm的大孔材料(Macroporous materials),孔径介于2～50nm的介孔材料(Mesoporous materials)和孔径小于2nm的微孔材料(Microporous materials)。但是,由于孔径的限制,这三类材料的应用均存在一定的局限性。多级孔材料兼具通透性好、孔隙结构发达、体积密度小、比表面积和孔体积大等优点,打破了传统单级孔材料孔结构单一的局限,因此越来越受到研究人员的关注。然而,多级孔材料在制备中仍存在较多问题。例如,其合成过程通常会涉及到两种及两种以上的方法,制备工艺复杂;现有的多级孔材料的制备成本高,孔结构难以控制。因此,研究者们主要从优化多级孔材料的制备工艺以及降低生产成本等方面入手,制备出孔径均一且可控的多级孔材料。多级孔材料主要有大孔-介孔材料(Macro-mesoporous materials)、微孔-介孔材料(Micro-mesoporous materials)以及含有两种或多种不同孔径的介孔-介孔材料(Meso-mesoporous materials)。大孔-介孔材料常见的制备方法有模板法、发泡法、溶胶-凝胶法及熔盐法等;微孔-介孔材料的主要制备方法有化学活化法、模板法和水热法等;介孔-介孔材料的制备方法主要有水热法、模板法、溶胶-凝胶法及自组装法等。本文综述了近年来多级孔材料的最新研究进展,分别对大孔-介孔、微孔-介孔及介孔-介孔材料的制备方法进行了介绍,并简要分析了未来本领域研究的发展趋势。

Research Progress of Hierarchical Porous Materials

Porous materials have been widely applied in adsorption and separation, catalyst supports, thermal insulating materials, energy storage, sensors, etc., owning to their high porosity, high surface area, low thermal conductivity and bulk density, and good chemical inertness. Porous materials can be classified into three categories according to pore size:macroporous materials with the aperture greater than 50 nm, mesoporous materials that possess a pore size between 2 nm to 50 nm and microporous materials with pore diameter less than 2 nm. However, their applications suppressed to a certain extent owing to the limited pore size. Hierarchical porous materials enjoy the advantages compared to the conventional porous materials including high permeability, elaborate pore structure, low bulk density, large surface area and pore volume, and have been provoking continuously increasing research interest. On the other hand, the conventional preparation process for hierarchical porous materials still suffer several problems, including complicated preparation process, high-cost preparation and difficulty in controlling pore structure. Thus, researchers endeavor to optimize hierarchical porous materialsfabrication process and reduce the cost of preparation, aiming to prepare uniform-and controllable-sized hierarchical porous materials. Hierarchical porous materials mainly include macro-mesoporous materials, macro-mesoporous materials and meso-mesoporous materials with bimodal or multiple mesopores. Macro-mesoporous materials can be produced by a variety of methods including template method, foam-gelcasting, sol-gel method and molten salt method. The major routes to preparing micro-mesoporous materials are chemical activation, template method and hydrothermal method. Meso-mesoporous materials are commonly fabricated through hydrothermal method, template method, sol-gel method and self-assembly synthetic procedure. This paper gives a summary of research efforts in recent years with respect to the hierarchical porous materials, and introduces the fabrication process of macro-mesoporous, micro-mesoporous materials and meso-mesoporous materials. The development trends of the future research are also discussed.