Size tailored bimetallic metal-organic framework (MOF) on graphene oxide with sandwich-like structure as functional nano-hybrids for improving fire safety of epoxy

Nano-hybrids of Zn and Co bimetallic metal-organic frameworks (MOFs) on graphene oxide (Zn/Co [email protected], hereafter [email protected]) with sandwiches structure were synthesized by a facile in-situ growth method. In order to achieve homogeneous growth of MOFs on GO layers, a new method, which is by adjusting the ratio of Zn and Co sources, was proposed to adjust the size and distribution of MOFs grown on GO. Uniform growth of MOFs on GO layers was found at the condition Zn/Co around 6/4. Optimal [email protected] nano-hybrids show an enhanced thermal stability due to the synergistic effect of the two materials and are employed in epoxy (EP) to reduce the fire hazard. Fire test results demonstrated that EP matrix with 2 wt % of [email protected] (EP/[email protected]), the peak heat release rate (pHRR) decreased by 30% and the limiting oxygen index (LOI) of EP composites increased from 23.4% to 29%. Moreover, [email protected] nano-hybrids significantly decrease the release of toxic gases, in particularly, the production of carbon monoxide (COP) decreased by 37% relative to pure EP. The storage modulus of EP/[email protected] also increased to 2002 MPa from 1714 MPa. The possible fire retardancy mechanism was proposed which involved the barrier effect of layered GO, superior catalytic oxidation effect of transition metal based MOF and its catalytic carbonization process. In perspective, MOF based hierarchical nano-hybrids open a feasible window in reducing the fire hazards and mechanical property of polymers.