Metal–Organic Frameworks–Based Flame-Retardant System for Epoxy Resin: A Review and Prospect

Metal-organic frameworks (MOFs), as a new family of nanomaterials with multiple dimensions, present enormous potential in different applications due to their high specific surface area and porosity, easy chemical functionalization, and excellent designability of nanostructure. These peculiar properties make MOFs promising alternatives as nanofillers for the fabrication of high-performance and multifunctional composites. In the past five years from 2017 to 2022, many researchers have investigated the flame retardant effects and mechanisms of MOFs in various polymeric materials. Statistical analysis based on bibliometrics showed that the research of MOFs flame retardant epoxy composites accounts for about 40% of the flame retardant field of MOFs, which is also very necessary to be sorted out separately. And to our knowledge there is no comprehensive report on MOFs flame retardant epoxy composites. Here, this review provides the latest advances of MOFs in flame retardant epoxy composites using pure MOFs, MOFs derivatives, functionalized MOFs, and synergistic systems based on MOFs and other functional components. The modification strategies and flame retardant efficiency of MOFs-based flame retardants are analyzed with special emphasis on the flame retardant mechanisms of different components. In addition, most MOFs-based flame retardant composites exhibit multiple functions that benefit from their inherent properties such as wave absorption as well as mechanical enhancement, thus promising in some high-end applications. Finally, the opportunities and challenges for the future development of MOFs-based flame retardants were summarized and prospected. This work is also expected to facilitate researchers to quickly understand the latest developments in this field and guide their effective design.