Generation of Hierarchical Porosity in Metal-Organic Frameworks by the Modulation of Cation Valence

Hierarchically porous metal-organic frameworks (HP-MOFs) have attracted great attention owing to their advantages over microporous MOFs in some applications. Despite many attempts, the development of a facile approach to generate HP-MOFs remains a challenge. Herein we develop a new strategy, namely the modulation of cation valence, to create hierarchical porosity in MOFs. Some of the Cu-II metal nodes in MOFs can be transformed into Cu-I via reducing vapor treatment (RVT), which partially changes the coordination mode and thus breaks coordination bonds, resulting in the formation of HP-MOF based on the original microporous MOF. Both the experimental results and the first-principles calculation show that it is easy to tailor the amount of Cu-I and subsequent hierarchical porosity by tuning the RVT duration. It is found that the resultant HP-MOFs perform much better in the capture of aromatic sulfides than the original microporous MOF.