Analysis of the porosity of ZIF-8 and ZIF-8@CNF membranes using positron annihilation lifetime spectroscopy (PALS)

Zeolite imidazole framework (ZIF) are a family of metal-organic frameworks with nano-sized pores that can be used as membranes for highly selective gas separation. Currently, efforts are being made to control the pore size of ZIF for gas separation based on their kinetic diameters. In this study, the effects of a surfactant and cellulose nanofiber (CNF) as a substrate on the pore and crystal sizes were investigated. We measure pore size using positron annihilation lifetime spectroscopy. Results showed that the pore size decreases as the crystal size decreases. The pore size of the ZIF-8 nanoparticles grown on the CNF is 0.45 nm.