Integration of metal-organic frameworks and clay toward functional composite materials

Metal-organic frameworks (MOFs) have become increasingly important as a class of porous crystalline materials because of their diverse applications. At the same time, significant progress has been achieved in the field of MOF-based composite materials toward novel applications based on the synergistic effect of two or more different components. Clay materials have been explored recently in MOF chemistry for the synthesis of MOF-clay composites, which are a new class of functional materials synthesized by a cooperative combination of MOFs with clay. Such composites have evolved only in the recent past with important functions and applications, such as enhanced gas storage and separation, CO₂ capture and conversion, catalysis, drug delivery, and water harvesting. Notably, the typical shortcomings of MOFs, such as moisture sensitivity, poor water dispersibility, poor thermal and chemical stability, and poor processability, could be overcome by developing novel MOF-clay composites. This article provides a concise overview of MOF-clay composites and their applications in various fields that will drive the interest of researchers to explore the emerging field of MOF-clay chemistry. In the initial sections, we classify the clays that have been used in MOF chemistry and briefly discuss their structures and chemistry. We also present the advantages of MOF-clay composites and discuss their synthetic methodologies. In the later sections, we classify different MOF-clay composites based on the clay and present some representative examples of such composites that show unique properties and applications. Finally, the development in this field is summarized, and the future scope of such composites is discussed.