Silane-networked UiO-66-NH₂ enabled high-performance composite proton exchange membrane in water electrolysis

Metal-organic frameworks (MOFs) have been widely used as high-performance proton-conducting materials of proton exchange membranes (PEMs) for efficient proton exchange membrane water electrolysis (PEMWE) due to their precisely tunable structures and versatile chemical functionalization. However, the poor distribution of MOFs within polymer matrices and their limited proton transport pathways remain substantial challenges. In this work, a silane-networking strategy is proposed to construct silane-networked UiO-66-NH₂ (Si-UiO-66-NH₂), which serves not only as a spatial barrier through Si-O-Si crosslinking to inhibit self-aggregation but also as a proton-conductive mediator via superficial polar groups that enhance proton transport. The resulting silane-networked MOFs exhibit enhanced interfacial compatibility with the Nafion matrix, thereby promoting uniform dispersion of MOF particles throughout the polymer network. More impressively, the abundant polar functional groups of silane-networked MOFs reorganize the hydrophilic/hydrophobic microphase-separated structure of the membrane, facilitating the formation of continuous, low-energy-barrier proton transport channels. Benefitting from these structural enhancements, the composite membranes exhibit excellent performance, including a low swelling ratio of 15.7 % at 80 °C and high proton conductivity (236.4 mS·cm^-1). When applied in a water electrolyzer, the optimized Si-UiO-66-NH₂@Nafion membrane results in a significantly reduced cell voltage of 1.887 V at a current density of 3.0 A·cm^-2 at 80 °C, representing a 15.3 % decrease compared to the system using recast Nafion. This work introduces an effective ionomer/filler interfacial modulation strategy to improve the water electrolysis performance of PEMs.