Enhancement of the Water Adsorptivity of Metal-Organic Frameworks upon Hybridization with Layered Double Hydroxide Nanosheets

Efficient water adsorbents with improved hydrostability can be synthesized by the hybridization of metal-organic framework (MOF) compounds with exfoliated layered double hydroxide (LDH) 2D nanosheets. The self-assembly between copper benzene tricarboxylate (Cu-BTC) MOF nanocrystals and exfoliated Mg-Al-LDH nanosheets leads to the nanoscale mixing of the MOF and LDH components, as well as to the prevention of the formation of aggregated secondary MOF particles. In the resulting nanohybrids, spherical Cu-BTC nanocrystals with small particle sizes of similar to 5-10 nm are uniformly anchored on the surface of Mg-Al-LDH 2D nanosheets with the dimensions of several hundred nanometers. At the optimal composition, the surface area of the resulting nanohybrid becomes greater than that of pristine Cu-BTC, which is attributable to the suppression of the self-aggregation of MOF nanocrystals and to the formation of the mesoporous stacking structure of the LDH nanosheets. Of prime importance is that both the water adsorption ability and the hydrostability of Cu-BTC become notably improved upon hybridization with LDH nanosheets. The present study clearly demonstrates that exfoliated LDH nanosheets can be used as an effective hybridization matrix for exploring novel efficient MOF-based hybrid water adsorbents.