Water-mediated synthesis of hydrogen-bonded metal–organic frameworks

The integration of different types of frameworks into one would provide a unique opportunity for the development of crystalline frameworks that can combine the unique advantages of each. In this work, we successfully realize the integration of metal-organic frameworks (MOFs) and hydrogen-bonded organic frameworks (HOFs) through the synthesis of two hydrogen-bonded metal-organic frameworks, namely NNM-1(M) (M = Cu or Ni). The structures of NNM-1 are built on (4, 4)-squared coordinative metal-organic layers. Between the layers, two adjacent protonated carboxylic groups serve as both hydrogen donors and acceptors, leading to the formation of hydrogen-bonded pillars with <i>R</i> ₂ ²(8) dimeric hydrogen bonding, the most common hydrogen-bonded motif in HOFs. It was found that water plays a vital role in the structural transformation from 3D MOFs to H-MOFs here. Under a low pressure of 0.1 bar, the material NNM-1(Cu) can adsorb 4.84 mmol g^-1 of NH₃, making it a promising adsorbent for ammonia capture.