Robust multifunctional Zr-based metal–organic polyhedra for high proton conductivity and selective CO2 capture

Abstract

New stable Zr-based metal–organic polyhedra (MOPs) have been designed and constructed through the self-assembly of a designed flexible sulfonate–carboxylate ligand, 1,2-bis(sodium-2-sulfonate-4-carboxyphenoxy)ethane (NaH₂L), and the secondary building units (SBUs) of Cp₃Zr₃(μ₃-O)(μ₂-OH)₃, (Cp = η⁵-C₅H₅). The MOPs feature candy-like cages and the anionic sulfonic groups on the organic ligand strengthened the stability of the MOPs (thermal stability and acid and alkali resistance) by forming strong multiple charge-assisted hydrogen bonds with the cationic SBUs. The unique cavities of this 3D porous framework endowed the MOPs with highly selective CO₂ capture. The 2D H-bond networks obtained by the connection of coordinated water molecules and free water molecules between the discrete MOPs enabled a high proton conductivity of 1.41 × 10⁻³ S cm⁻¹ at 30 °C, 98% relative humidity (RH) and a low activation energy of 0.225 eV for the proton transfer.