A facile synthesis of monolithic MOF single crystal for gas separation via a supersaturation strategy

Large-area metal–organic framework (MOF) single crystal membrane materials hold great appeal in gas separation field due to their outstanding separation selectivity and permeability. Nevertheless, it is currently difficult to prepare MOF single crystals large enough for gas separation tests owing to the limited manufacturing processes. In this work, we fabricate a self-supporting MOF single crystal (Co-btec SC) membrane with 0.3 × 0.1 cm2 dimension via a facile supersaturation synthesis strategy. Benefiting from the one-dimensional (1D) transmission pathway and three-dimensional (3D) connection network, the obtained Co-btec SC has ultra-high permeability of 47,647 Barrer. Besides, the H2O molecules firmly filled in the pore channels greatly improve the affinity and solubility for CO2, and thus Co-btec SC yields CO2 preferential permeation in CO2/H2 mixture with superior CO2/H2 selectivity of 18.79. In addition, the Co-btec SC shows dramatic high-temperature and high-humidity separation stabilities. To demonstrate the versatility of this strategy, we also successfully fabricated hydrogen-bonded organic framework single crystals (HOF SCs) with the size of about 0.4 cm. This supersaturation strategy opens a new way to fabricate the large-area MOF single crystal membranes.