Preparation of Covalent-Ionically Cross-Linked UiO-66-NH₂/Sulfonated Aromatic Composite Proton Exchange Membranes...

Metal-organic frameworks (MOFs), as newly emerging filler materials for polyelectrolytes, show many compelling intrinsic features, such as variable structural designability and modifiability of proton conductivity. In this manuscript, UiO-66-NH₂, a stable MOF with -NH₂ functional groups in its ligands, was selected to achieve a high-performance sulfonated poly(arylene ether nitrile)s (SPENs)/UiO-66-NH₂-x covalent-ionically cross-linked composite membrane. Simultaneously, the obtained composite membranes displayed excellent thermal stability and dimensional stability. The as-prepared SPEN/UiO-66-NH₂-x cross-linked membranes exhibited higher proton conductivity than recast SPENs, which can be attributed to the construction of ionic clusters and well-connected ionic nanochannels along the interface between UiO-66-NH₂-x and SPEN matrix via molecular interactions. Meanwhile, the methanol permeability of the SPEN/UiO-66-NH₂-x composite membrane had been effectively reduced due to the barrier effect of cross-linking and the addition of UiO-66-NH₂-x. The SPEN/UiO-66-NH₂-5 composite membrane had the highest selectivity of 6.42 × 10⁵ S·s·cm^-3: 14.3-times higher than that of Nafion 117. The preparation of cross-linked UiO-66-NH₂/SPEN composite was facile, which provides a new strategy for preparing high performance proton exchange membrane.