Herein, we demonstrate thermally rearranged polybenzoxazole-co-imide (TR-PBOI) electrospun nanocomposite membranes for membrane distillation and membrane crystallization applications. We seek to demonstrate that a synergistic combination of TR polymers, porous nanofibrous membranes, and particle coating improves the long-term stability while maintaining high porosity and water flux. The fabricated membranes exhibit an excellent water flux (80 kg m(-2) h(-1)) and NaCl rejection (499.99%) with steady performance over more than 186 hours. In addition, for the first time, controlling the heterogeneous nucleation phenomena in membrane crystallization was clearly demonstrated using TR membrane morphology.