有机物单层分散在相关材料制备中的应用

与无机氧化物和盐类在载体表面自发单层分散相类似, 许多有机物也可以在载体表面自发单层分散.有机物在载体表面单层分散行为和分散后的存在状态与有机物分子形状和结构特点及载体表面性质和孔结构有关. 利用有机物在载体表面的单层分散, 可以设计制备具有优异性能的材料. 本文简要综述了近年来这方面研究工作取得的相关进展, 主要介绍了有机物单层分散在碳/氧化物复合物、氧化物和薄壁中孔碳材料的制备和织构调控方面的一些应用实例. 单层分散的有机物热分解后可在载体表面形成均匀的薄碳层, 以无机多孔氧化物为载体可制备出包覆均匀碳薄层的碳/氧化物复合物, 这种碳/氧化物复合物在染料吸附、催化剂载体和光催化方面显现出好的性能. 以溶胶-凝胶法制备氧化物时, 分散的有机物可以隔离溶胶颗粒, 从而制备出高比表面积的氧化物并可对孔容进行调控, 以此方法制备的γ-氧化铝比表面积可达506 m²·g^-1. 在惰性气氛中加热上述碳/氧化物复合物, 碳层可抑制氧化物的相变; 而在氧气中, 碳层燃烧发热会促进相变, 由此可快速制备超细α-氧化铝. 包覆均匀碳薄层的氧化物载体对碳起支撑作用, 在将氧化物溶解去除后, 可便捷制得高比表面积、大孔容、高中孔率的薄壁中孔碳材料, 碳材料的形貌、孔径分布等可通过选用不同织构的氧化物载体进行调控.

Applications of Monolayer-Dispersed Organic Compounds in the Preparation of Related Materials

Many organic compounds will spontaneously disperse on the surface of a solid support to form monolayers, in a manner similar to that of inorganic salts and oxides, and numerous materials with useful properties can be designed and prepared based on this phenomenon. The dispersion behavior and orientation of organic compounds in monolayers depend not only on the molecular structure of organic compounds but also on the surface features and pore structure of the support. This short review summarizes the applications of monolayer-dispersed organic compounds in the preparation and texture control of related materials, including carbon/oxide composites, various other oxides, and mesoporous carbon with thin pore walls. Pyrolysis of organic monolayers can be used to prepare carbon/oxide composites with a uniformly thin carbon layer for use as photocatalysts, catalyst supports, and adsorbents for dyes. During the sol-gel preparation of porous oxides, organic monolayers can also prevent the aggregation of sol particles, thus producing oxides with high specific surface areas and adjustable pore volumes; γ-Al₂O₃ with a specific surface area as high as 506 m²·g^-1 can be prepared in this manner. During calcining under an inert atmosphere, the carbon layer in the aforementioned carbon/oxide composites can significantly inhibit the phase transformation of oxides. Calcining carbon/γ-Al₂O₃ in oxygen at high temperatures, however, results in a rapid γ to α phase transformation. The oxides in these composites can also act as templates for the preparation of carbon materials. Dissolving the support oxides is a convenient method for the preparation of mesoporous carbon materials with high specific surface areas, large pore volumes, high mesopore ratios, and thin pore walls. The morphology and size distribution of pores in these carbon materials can be controlled by choosing oxides with different textures.