Freeze-enabled synthesis of functional materials: fundamental, progress, and applications

Ice-templating, or more broadly, freezing-enabled processing and synthesis, is a highly versatile approach to fabricating a wide range of porous, nanostructured, and functional materials. These materials have been extensively explored in the fields of engineering, energy storage, thermal management, wave shielding, biomedical applications, environmental remediation, and catalytical reactions, etc. The research in this topic has been continuously going strong and indeed has attracted intensive efforts from scientists across diverse research fields in recent years. In this review, we first describe key aspects and key parameters of freezing process and freeze-drying for the preparation of ice-templated materials. The understanding and control of freezing process is essential for many other processes, e.g., cryopreservation, freeze-desalination, although they are not covered in this review. This is followed by the production of biopharmaceuticals by freezing and freeze-drying. We then demonstrate how the freezing process can be applied to prepare a wide range of porous and nanostructured materials, organized by the materials morphologies. We further describe how freezing reaction and the synthesis of functional materials, particularly 2D materials, are enabled via freeze-concentration and catalytic property of ice surface. The applications of the ice-templated materials in diverse fields are then reviewed, with a focus on recent progress and how the ice-templated features and freeze-drying enhance the performance in these applications. This comprehensive review is completed with a conclusion and proposed challenges in moving this research field ahead.