Superprotonic conductivity of Ti-based MOFs with Brønsted acid–base pairs

[Display omitted] •(NH2)x-MIL-125 (x = 0, 1 and 2) were one-pot direct synthesized, high proton conductive complex, H2SO4@(NH2)x-MIL-125 (x = 0, 1 and 2), were successfully developed by a facile impregnation approach.•The unique Brønsted acid–base pairs formed between H2SO4 and amino groups of MOF build high-density H-bonding networks, resulting in outstanding proton conductivity.•The H2SO4@(NH2)2-MIL-125 exhibits the high proton conductivity of 10−2 S cm−1 at 98% RH & 80℃, comparable to the results obtained for other MOF-based materials under similar conditions. Fuel cells technology demands high and stable proton-conductivity electrolyte materials. Here we show an effective approach of H2SO4 impregnation into Ti-based metal–organic framework (Ti-MOFs, (NH2)x-MIL-125 (x = 0, 1 or 2)), attains high proton-conductivity. The proton conductivity increases for increased amino functional groups on H2SO4@(NH2)x-MIL-125 (x = 0,1 or 2). The superproton conductivity, attributed to the abundant dangled amino functional groups, through an enhanced Brønsted acid–base pairs with sulfonic acid. Notably, the H2SO4@(NH2)2-MIL-125 measured to be superprotonic conductivity of 2.2 × 10−2 S cm−1 under 98% RH &80 °C, thus competes with the most popular electrolyte, such as Nafion. In addition, the composite appeals required characteristics of easy operation, and good stability.