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incorporating additional flame-retardant elements, such as phosphorus or nitrogen, into the MOF structure
during post-treatment, their flame retardancy can be enhanced; (2) This method involves breaking the
coordination bonds between the metal ions and the ligands in the MOF, which allows for the creation of a
hybrid material that inherits some desirable properties of the original MOF, while also introducing new
features; (3) Generating expanded pores: post-treatment of MOFs can create larger pores or expand existing
ones, which can improve their ability to adsorb volatile organic compounds and harmful gases produced
during polymer combustion. The expanded pores can be used as a carrier to load phosphorus-based flame
retardants, which can further improve the flame retardancy of MOFs. Zhao et al. transformed the
microporous structure of MIL-53 into macropores via ammonia water treatment under closed conditions,
[21]
thereby enhancing its specific surface area and adsorption capacity . The excellent porous architecture was
then utilized for triethyl phosphate (TEP) adsorption as a flame retardant in polystyrene and (4) Controlling
morphology: multi-level pore structures can provide more active sites for catalytic reactions. Hollow
structures can reduce the weight of flame retardants, which can improve their dispersion and increase the
number of active sites available for flame retardancy. As a result, the flame-retardant efficiency has been
significantly enhanced while minimizing any adverse effects on the mechanical properties of EP composites.

OUTLOOK
This perspective provides a concise overview of the latest research advances in MOF flame retardants and
offers insights into their prospects. Compared to other commonly used fillers, such as platelet-like clay,
carbon-based fillers, and silicates, MOFs offer several distinct advantages: In Gas-Phase, Certain MOFs
containing nitrogen or phosphorus-containing organic ligands exhibit gas-phase action, effectively trapping
active radicals and diluting combustible gases. This gas-phase action contributes to the overall flame
retardancy of polymers by interrupting the combustion chain and reducing the availability of flammable
gases. In the condensed phase, the metal ions or clusters present in MOFs act as catalytic centers, promoting
char formation during combustion. This catalytic activity enhances the formation of a protective char layer,
which acts as a barrier against heat and mass transfer, thereby improving the flame retardancy of the
polymer. Furthermore, MOFs offer a high degree of tunability, allowing for the customization of their
properties to suit specific applications. The pore size, surface area, and composition of MOFs can be tailored
to optimize flame retardant performance and address specific requirements of the polymer matrix. These
advantages position MOFs as promising alternatives to conventional flame-retardant fillers.

The cost outlook of MOF flame retardants is an important consideration for their widespread adoption in
various industries. The cost of MOF flame retardants is influenced by several factors, including the cost of
raw materials, the synthesis process, and the scale of production. One approach to reducing their cost is to
optimize the synthesis process. The development of more efficient and scalable synthesis methods can
reduce the cost of production and increase the yield of MOFs. Additionally, the use of cheaper starting
materials and reagents can also lower the cost of MOF flame retardants. Another approach to improving the
cost-effectiveness of MOF flame retardants is to increase their functionality and versatility. By designing
MOFs with multiple functions, their value proposition can be increased, which can justify the higher cost.
In addition to industrialization, researchers are also striving to develop multifunctional MOFs that can
perform multiple tasks simultaneously. These types of MOFs can be engineered not only for flame
retardants but also for gas absorption, antibacterial activity, or pollutant filtration. Ligand synthesis and
derivatives are also important areas of research in the development of MOFs for flame retardant
applications. By designing novel ligands and derivatives, researchers can precisely adjust the properties of
MOFs to enhance their efficacy in fire suppression. Altering the structure of ligands or introducing new
functional groups can elevate the thermal stability or augment the flame-retardant characteristics of MOFs.