Magnetic orientation behavior of L-type zeolite with rare-earth elements under low magnetic field

The magnetic orientation of L-type zeolite ion-exchanged with various rare-earth elements was observed under a low magnetic field of 0.9 T. The orientation along the applied magnetic field was classified into three types: c-axis orientation for Ce³⁺, Pr³⁺, Nd³⁺, Tb³⁺, Dy³⁺ and Ho³⁺, ab-plane orientation for Er³⁺, Tm³⁺ and Yb³⁺, and random orientation for Eu³⁺ and Gd³⁺. The different orientation behavior was considered to originate from the electronic structures of the rare-earth ions introduced into the zeolite structure.

Macroscopically Oriented Porous Materials with Periodic Ordered Structures: From Zeolites and Metal-Organic Frameworks to Liquid-Crystal-Templated Mesoporous Materials

Porous materials with molecular-sized periodic structures, as exemplified by zeolites, metal-organic frameworks, or mesoporous silica, have attracted increasing attention due to their range of applications in storage, sensing, separation, and transformation of small molecules. Although the components of such porous materials have a tendency to pack in unidirectionally oriented periodic structures, such ideal types of packing cannot continue indefinitely, generally ceasing when they reach a micrometer scale. Consequently, most porous materials are composed of multiple randomly oriented domains, and overall behave as isotropic materials from a macroscopic viewpoint. However, if their channels could be unidirectionally oriented over a macroscopic scale, the resultant porous materials might serve as powerful tools for manipulating molecules. Guest molecules captured in macroscopically oriented channels would have their positions and directions well-defined, so that molecular events in the channels would proceed in a highly controlled manner. To realize such an ideal situation, numerous efforts have been made to develop various porous materials with macroscopically oriented channels. An overview of recent studies on the synthesis, properties, and applications of macroscopically oriented porous materials is presented.