Facile and reversible digestion and regeneration of zirconium-based metal-organic frameworks

The digestion/regeneration of metal-organic frameworks (MOFs) has important applications for catalysis, drug delivery, environmental decontamination, and energy storage, among other applications. However, research in this direction is limited and very challenging. Here, we develop a facile method to digest and regenerate a series of zirconium-based metal-organic frameworks (Zr-MOFs) by bicarbonate or carbonate salts. As an example, UiO-66 demonstrates well the mechanism of reversible digestion/regeneration processes. By analyzing the digested zirconium species via X-ray diffraction, Fourier transform infrared spectroscopy and Raman scattering spectroscopy, a digestion mechanism based on the formation of dissoluble complexes [Zr₂(OH)₂(CO₃)₄]^2- is proposed. Impressively, ultrafine Pd nanoparticles can be extracted from Pd@PCN-224 via this strategy. This work, thus, may provide new insight for the development of renewable MOFs and their practical applications.