Tuning humidity response in 2D MOF membranes through nanosheet geometry.

Variations in the geometry of two-dimensional metal-organic framework (2D MOF) nanosheets provide an effective handle for tuning the humidity response of lamellar membranes. Using layered CuTCPP as a model system, we show that membranes assembled from smaller and thinner nanosheets exhibit up to a 37-fold enhancement in humidity sensitivity compared with those composed of larger and thicker counterparts. Reducing nanosheet thickness and lateral size increases the accessible nanosheet surface within the lamellar architecture and promotes more uniform stacking with confined interlayer voids. These surface-dominated structural features facilitate the formation of continuous, water-mediated charge transport pathways. As a result, the membranes display faster response kinetics, higher steady-state currents, and enhanced low-humidity performance. This work establishes a clear geometry-structure-property relationship and highlights nanosheet surface accessibility as a key factor governing humidity-responsive transport in 2D MOF membranes.