Single-Anion Conductor Enabled by Quaterization and Ion Exchange in an Imidazole-Modified Metal–Organic Framework

Metal-organic frameworks (MOFs) have emerged as hydroxide conductors for alkaline membrane fuel cells due to their porosity, designability, and ease of functionalization. However, related frameworks, especially single OH^- conductive MOFs, are rarely reported because it is difficult to simultaneously balance efficient hydroxide conductivity and high base stability. We synthesized a stable hydroxide ion conductor, [Zr₆(μ₃-O)₄(μ₃-OH)₄(Meim-BDC)₆](OH^-)₆ [<b>Meim(OH</b>^<b>-</b><b>)-UiO-66</b> or <b>SXE-6</b>, where <b>SXE</b> = Shanxi electrolyte and Meim-H₂BDC = 2-(methylimidazol-1-yl)terephthalic acid], through quaterization of N atoms and subsequent ion exchange of [Zr₆(μ₃-O)₄(μ₃-OH)₄(Im-BDC)₆] [<b>Im-UiO-66</b>, where Im-H₂BDC = 2-(imidazol-1-yl)terephthalic acid]. Compared to the original neutral network material, the conductivity of the modified material is increased by 10 times, up to 3.44 mS cm^-1 at 80 °C and 99% relative humidity. It should be pointed out that <b>Meim(OH</b>^<b>-</b><b>)-UiO-66</b> represents the single OH^- conductor with the highest conductivity in pure MOFs. What is more, a conductive mechanism is visually exhibited by molecular dynamics simulation, suggesting Grotthuss-like migration in void spaces.