Space‐Confined Water Isotope Transport in Conductive MOF Thin Film

ABSTRACT 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 (Cu 1 TPB 0.1 − x C) 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 H 2 O and D 2 O 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 Cu 1 TPB 0.1 − x C 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 H 2 O and D 2 O 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.