Interlayer Confinement Strategy in Two-Dimensional Polyoxometalate-Based Metal–Organic Frameworks for Enhancing Proton Conduction

Proton exchange membranes are crucial components in electrochemical
energy devices. Nevertheless, the development of high-performance
proton-conducting materials remains a considerable challenge, primarily
due to the inherent difficulty in constructing dense and continuous
hydrogen-bonding networks under ambient conditions. To overcome this
limitation, the intentional incorporation of short hydrogen bonds
has been applied as a critical design strategy and plays a critical
role in enabling efficient proton transport. In this work, we adopt
an interlayer confinement strategy to enhance proton conductivity
by introducing chitosan into a newly developed two-dimensional (2D)
layered polyoxometalate-based metal–organic framework (POMOF),
{[Cu2(4-abpt)2][Cr(OH)6Mo6O18]} (CUST-877). The introduction of chitosan promotes
the formation of continuous hydrogen-bonding networks and facilitates
efficient proton transfer pathways within the layered structure. By
regulating the interlayer spacing of the POMOF structure, the CS/CUST-877-10
composite exhibits a proton conductivity of 4.52 × 10–3 S cm–1 at 98% RH and 80 °C, which is 2 orders
of magnitude higher than that of the pristine CUST-877. This work
offers a new design concept for the development of POM-based proton
conductors and highlights the potential of polymer-modified 2D-MOF
systems for energy conversion technologies.