Designs and developments of proton conductors are highly important in chemistry and energy fields. In this study, a novel metal-organic framework H 2 DAB-MgNi(ox) 3 was synthesized. X-ray powder diffraction, scanning transmission electron microscopy, and scanning transmission electron microscopy-energy-dispersive X-ray mapping measurements demonstrated that the H 2 DAB-MgNi(ox) 3 had a solid-solution structure, with the homogeneous distribution of Mg and Ni elements. The proton conductivity of H 2 DAB-MgNi(ox) 3 was enhanced from that of H 2 DAB-Ni 2 (ox) 3 at 95% relative humidity by Mg substitution.