MXene has been the subject of various studies and applications in polymer composites in recent years. However, its compatibility with hydrophobic polymers has been a significant limitation. This study presents a simple way to create MXene frameworks to realise flame retardant hydrophobic polymer composites. The fabrication process is environmentally friendly and low-cost. The PVB/HPUPO/MXene composite membrane showed a 74.7% reduction in volatile intensity during thermal degradation compared to pristine PVB. The PVB/HPUPO/MXene composite membrane also demonstrated significantly improved flame retardancy compared to pure PVB. Specifically, MXene based networks and HPUPO showed synergistic effect in improving the fire safety of PVB composites. This study offers a new approach to incorporating MXene as a flame retardant into conventional phosphorus- and nitrogen-based flame retardant systems for hydrophobic polymers with great fire retardancy.