Shaping of ZIF-8 upon EPR control for efficient uptake of guest molecules

Shaping of metal-organic frameworks (MOFs) is one of the crucial steps toward their industrial applications. A number of methods for preparation of pellets containing MOF-micro/nanoparticles have been developed up to date; however, the uptake rates of guest molecules by such shaped MOFs and their dependence on preparation procedure were not analyzed in detail. Since optimization of the uptake rates is vital for practical use, in this work we employ spin-probe Electron Paramagnetic Resonance (EPR) to study solvent diffusion into ZIF-8 based pellets. This dedicated approach allows one to selectively monitor the impregnation of ZIF-8 particles embedded in the pellet, and corresponding diffusion coefficients can be obtained for the molecules of interest. Optimization of shaping procedure upon EPR control yields robust pellets with pore filling rates comparable to those for powdered ZIF-8. The proposed methodology yielded highly permeable ZIF-8-based pellets and is promising for future application in shaping of various MOFs.