Moreover, the membrane morphology is like the phase-separated structure; the phase to retain the membrane form is the substrate with mechanical strength, and the phase for proton conduction is only ZrP without additional electrolyte polymer. Firstly, a zirconium acetylacetonate, the precursor of the ZrP-based inorganics (AcAc-Zr) membrane, was created by filling AcAc-Zr into a porous substrate. Several porous substrates (pore size: 100 nm, 70 nm, 50 nm, 30 nm, 20 nm, and 16 nm) were employed to know the influence of pore size. Intriguingly, the high filling contents were achieved only when the pore size was below 30 nm. Next, we confirmed that the Acac-Zr in the membrane was converted to ZrP, zirconium amino-tris-methylene-phosphonate (ZrATMP), and zirconium 1-hydroxy ethylidene-1,1diphosphonate (ZrHEDP), which demonstrated that our methods could fabricate pore-filling membrane with various inorganics. With the membrane filed with a high content of ZrP derivatives, a wide range of applications is expected.