Tuning framework flexibility of MOF nanosheet membranes with heteroleptic 2D-3D linkers for H2/CO2 separation

Two-dimensional metal–organic framework (MOF) membranes have emerged as competitive candidates for efficient gas separation owing to their ultrashort diffusion pathways and highly tunable nanochannels. However, unavoidable linker rotation within 2D frameworks constrain accurate molecular sieving. Herein, heteroleptic Zn(bim)(OAc) nanosheets are employed for constructing high-performance membranes, where cooperative 2D-3D linkers coupling regulates framework motions. The 3D acetate (OAc − ) linkers limit the amplitude of motion, whereas planar 2D benzimidazolate (bim) linkers introduce locally rotational freedom through weaker M−N coordination bond, generating precise angstrom-level, dynamically tunable pore window. The heteroleptic membrane achieves considerable H 2 /CO 2 selectivity of ∼ 134, surpassing the upper bounds of traditional polymer membranes. This work demonstrates that cooperative 2D-3D linkers coupling provides a feasible pathway to engineer precise, dynamically tunable apertures in 2D MOF nanosheet membranes, offering a promising avenue for designing high-performance membranes.