Space-Confined Water Isotope Transport in Conductive MOF Thin Film.

The century-old challenge of isotope separation might be addressed by conductive metal-organic framework (cMOF) thin films featuring ordered nanopores, designable charge-transport pathways, and potential flexibility. However, resolving and amplifying the microscopic kinetic differences between water isotopologues within such confined spaces remains nontrivial. In this work, proton- and electron-coupled two-dimensional π-conjugated cMOF thin films (Cu1TPB0.1-xC) are fabricated through controllable layer-by-layer growth with oriented narrow pores and flexibility. Correlating electrical- and mass-transduced gas-sensor technologies, the subtle differences in the interactions of H2O and D2O with the framework were identified, revealing a complex multistage mass transport. Comparison of cMOFs with different pore sizes shows that this identification originates from distinct conduction mechanisms. Notably, the Cu1TPB0.1-xC thin film with a strong space-confined effect exhibits a complex multistage electrical response due to its unique proton-electron-coupled conduction characteristics, thereby enabling further differentiation of the transport processes of H2O and D2O on the outer surface and within the confined spaces. The oriented cMOF films therefore provide a real-time platform for resolving and amplifying subtle isotope-dependent transport dynamics in confined pores, offering mechanistic guidance for the design of porous materials with controlled water-isotopologue transport.