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Table 2. Industrial methods of MOF-based flame retardants
Method Description Example applications
Continuous flow MOFs are synthesized in a continuous flow system, where reactants are Large-scale production of MOFs
reactors continuously pumped through a reactor
Spray-drying A solution of MOF precursors is atomized into a hot drying gas, allowing Production of MOF powders for various
rapid solvent evaporation and MOF formation in the form of dry powder applications such as coatings and composites
Freeze-drying MOF precursors are dissolved in a solvent, frozen, and then subjected to a Production of highly porous MOFs with
vacuum, causing the solvent to sublime. The resulting solid is a porous MOF preserved crystallinity

Figure 2. Industrial application of MOF-based flame retardants.

of MOF ligands can be influenced by a range of factors, such as the availability of raw materials used for
synthesizing the ligands, the complexity involved in their synthesis, and the demand for MOF materials
across various industries. With the advancement of novel and more efficient synthesis techniques, there is a
possibility for a reduction in the cost of MOF ligands. As scientists have gained an enhanced
comprehension of the structure and characteristics of MOFs, they have been able to optimize the
production process of organic ligands that are utilized in creating these materials [40,41] . This has resulted in
more efficient and cost-effective approaches to synthesizing MOF ligands, thereby contributing to a
reduction in their price. By reducing costs through economical synthesis and purification methods, MOFs
can become more competitive with other materials, leading to increased adoption in industrial applications.

Combination of MOFs with other flame retardants
In this context, the commercial potential of incorporating MOFs as flame retardants into polymers has been
demonstrated due to the decreasing cost of synthetic organic ligands. Recent unpublished work and
conference papers have reported on MOFs acting as synergists with traditional flame retardants [Table 3].
MOFs can be added to other flame-retardant materials to enhance their performance [18,42-48] .

For example, MOFs can be added to intumescent coatings, which expand when exposed to heat, forming a
protective layer that insulates the underlying material and delays its ignition. The thermal stability of the
expanded coatings can be improved by adding MOFs; the coking property can be increased by transition
metal catalysis, and the flame-retardant property can be enhanced. Shen et al. investigated the use of MOFs
as a synergist for intumescent flame retardants in polypropylene (PP). The aim was to utilize ZIF-8 for
enhancing char formation and improving fire retardancy of PP. It was discovered that the incorporation of
ZIF-8 facilitated better char formation and reduced the emission of flammable gases during combustion .
[42]