A Lanthanum Polyoxometalate–Organic Framework with Abundant Intrinsic Proton Sources Enabling Ultrahigh Proton Conduction

Abstract Intrinsic proton sources and hydrolytic stability are two important elements of efficient proton-conducting materials for enhancing proton conductivity and reduced dependence on external environment. Herein, we report a lanthanide polyoxometalate–organic framework prepared using edta as a chelator, with coordinated and lattice water molecules acting as intrinsic proton sources. The material exhibits high proton conductivity even at 40% relative humidity and 298 K, retaining 2.6 × 10–4 S cm–1 with only a 4.6-fold decrease from the value of 1.19 × 10–3 S cm–1 at 95% relative humidity. This demonstrates weak humidity dependence, a key advantage over materials requiring conditions near saturation. At 373 K and 95% relative humidity, the conductivity reaches 1.76 × 10–2 S cm–1. Our findings offer a viable design for proton conductors that depend on internal water reservoirs.