In this work, iron-based and cobalt-based metal−organic frameworks (MOFs) were successfully synthesized by a facile solvothermal method. The obtained MOFs were added into polystyrene (PS) as flame retardants for the first time. The results of thermal gravimetric analysis and cone calorimetry indicated the addition of MOFs significantly enhanced the thermostability and flame retardancy of the PS composites. Compared with that of neat PS, greater than 14% and 28% decreases in the peak heat release rate were observed for PS/Fe-MOF and PS/Co-MOF, respectively, suggesting a flame retardant effect of MOFs. Based on thermogravimetric analysis−infrared spectrometry results and the analysis of combustion residues, the possible mechanism of the enhanced thermostability and flame retardancy of the PS composites was proposed as the combination of thermal barrier effect and catalytic effect of MOFs, which would allow promising application in the development of fire safety polymer materials.

Co-based metal-organic framework (Co-MOF) nanosheets were successfully synthesized by the organic ligands with Schiff base structure. The laminated structure gives Co-MOF nanosheets a great advantage in the application in the flame retardant field. Meanwhile, -C═N- from Schiff base potentially provides active sites for further modification. In this work, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was used to modify Co-MOF (DOPO@Co-MOF) to further enhance its flame retardant efficiency. It is attractive that DOPO has a synergistic effect with Co-MOF on improving fire safety of poly(lactic acid) (PLA). The obvious decrease in the values of peak heat release (27%), peak smoke production (56%), and total CO yield (20%) confirmed the enhanced fire safety of PLA composites. The possible flame retardant mechanism was proposed based on characterization results. Moreover, the addition of DOPO@Co-MOF had a positive influence on the mechanical performance, including tensile properties and impact resistance. This work designed and synthesized two-dimensional MOFs with active groups. As-prepared Co-MOF with expected structure shows a novel direction of preparing MOFs for flame retardant application.

No abstract

In this work, flowerlike nickel 2-methylimidazole metal–organic framework (Ni-MOF) was prepared by a solvothermal method. Vertically aligned Ni-MOF was fabricated from graphene oxide (GO) solution in the same way. The combination of GO and Ni-MOF (GOF) obviously suppressed the agglomeration of Ni-MOF sheets. As-synthesized, GOF has bigger pore volume and specific surface area, which are beneficial for volatile degradation products adsorption. It is noteworthy that the addition of GOF obviously reduced the fire hazard of polystyrene (PS). More than 33% decrease in the peak heat release rate for the PS/GOF composite was obtained when the content of the additives is only 1.0 wt %. Meanwhile, the reductions of total smoke and CO production were also prominent during the combustion of PS/GOF, respectively 21% and 52.3% decreases compared with that of pure PS. The synergism effects between layered GO and porous Ni-MOF realized the improved performances of PS. Thus, this work paves a feasible pathway to design efficient flame retardants for enhancing fire safety of polymers.

No abstract