Accurate stacking engineering of MOF nanosheets as membranes for precise H2 sieving

Two-dimensional (2D) metal-organic framework (MOF) nanosheet membranes hold promise for exact molecular transfer due to their structural diversity and well-defined in-plane nanochannels. However, achieving precise regulation of stacking modes between neighboring nanosheets in membrane applications and understanding its influence on separation performance remains unrevealed and challenging. Here, we propose a strategy for accurately controlling the stacking modes of MOF nanosheets via linker polarity regulation. Both theoretical calculations and experimental results demonstrate that a high linker polarity promotes neighboring nanosheets to a maximum AB stacking due to steric hindrance effects, leading to a controlled effective pore size of the membrane and consequently to improved molecular sieving. Among series of CuBDC-based 2D MOFs with different linkers, the CuBDC-NO2 nanosheet membranes exhibit a reduced effective stacking aperture of 0.372 nm, yielding H2 permeance of 4.44 × 10−7 mol m−2 s−1 Pa−1 with a high H2/CO2 and H2/CH4 selectivity of 266 and 536, respectively. This work represents the in-depth investigation of the accurate tuning of MOF nanosheet stacking in the field of 2D materials, offering more perspectives for broader applications with universality for various 2D materials. The authors propose a strategy to adjust the stacking modes of MOF nanosheets via linker polarity differences. Simulations and experiments reveal that higher linker polarity favors AB stacking, optimizing membrane aperture and enhancing gas sieving.