Freeze-casting in synthetic porous materials: Principles, different dimensional building units and recent applications

Freeze-casting (ice templating or freeze-drying) is a flexible and universal technique to create architectures with a unique porous structure based on almost all kinds of nanomaterials with any dimensions, rendering them with enormous potential applications in multifarious fields. Despite growing concern has been raised, there are still limited reviews on freeze-casting porous materials related to their principles, classification of building units and recent applications. To this end, in this review, first of all, the principles of freeze-casting are introduced and the effects of influencing factors on the structure of porous materials are explored. Secondly, different building units based on dimensions for freeze-casting porous materials are classified in detail. Thirdly, recent emerging progresses and applications on freeze-casting porous materials are summarized, including biomaterials, electrical application, thermal insulation, environmental application, sensors/smart materials and catalytic applications. Finally, the practical limitations and the bright prospects of freeze-casting are pointed out. We believe this review can furnish guidance and shed lights on the designing and application of freeze-casting porous materials.