Emerging MXene and covalent-organic framework hybrids: Design strategies for energy, sensing, and environmental applications

The demand for developing advanced hybrid materials with improved functions and performance is rising due to the current challenges in the environmental and energy fields. Hybridization of nanomaterials can address the shortcomings of individual components and afford composite nanomaterials with improved performance through synergistic effects. MXenes are among the growing families of inorganic two-dimensional (2D) materials with unique properties such as high electrical conductivity, hydrophilicity, easy processability, and excellent photothermal and electrochemical characteristics. Some limitations of MXenes, including poor chemical stability in oxidative conditions and low porosity due to restacking the 2D flakes, could hinder their potential in environmental applications. On the other hand, covalent organic frameworks (COFs) are highly porous organic networks but with primary shortcomings of low electrical conductivity and poor processability. Combining the metallic conductivity and excellent photothermal and electrochemical properties of MXenes with the high porosity of COFs enables the formation of COF@MXene nanomaterials with improved properties. Here, we provide a comprehensive review of the strategies utilized for designing and fabricating COF@MXene heterostructures through chemical and physical hybridization. The synergistic effects of hybridization are discussed for diverse applications, including catalysis, energy storage materials, sensors, water purification, and anti-corrosion coatings. Finally, the future outlook of the COF@MXenes, their challenges and possible solutions for these challenges are discussed.