(17e) Electron Beam Induced Modification of ZIF-8 Membrane Permeation Properties | AIChE

(17e) Electron Beam Induced Modification of ZIF-8 Membrane Permeation Properties


Miao, Y. - Presenter, Johns Hopkins University
Tsapatsis, M., Johns Hopkins University
Ionizing radiation is widely used in material processing applications ranging from polymer functionalization to medical equipment sterilization. Recent reports show that metal-organic frameworks (MOFs) undergo significant structural transformation under electron and X-ray irradiation. However, irradiation-induced modification of MOFs in gas separation applications has not been explored.

Here we report that electron irradiation can be used to modify the gas permeation properties of a prototypical MOF, ZIF-8, as demonstrated by improved CO2/N2 and CO2/CH4 selectivity in electron irradiated ZIF-8 membranes. ZIF-8 membranes were exposed to an electron flood gun operation at 2 kV for various time and single gas permeances of H2, CO2, N2 and CH4 were measured. The irradiated membranes show reduced permeation for all gases, among which CO2 is least affected at short exposure time. After irradiation for 1 min, the CO2/N2 and CO2/CH4 selectivity of the ZIF-8 membrane increases to 6.3 and 4.2 and corresponds to 3.8- and 3.2-fold increase, respectively. The gas separation performance of the membrane is stable during 23-80 °C temperature cycling over two weeks. After longer treatment of 5 and 100 min, permeances of all gases decrease dramatically in the ZIF-8 membranes, suggesting significant structural changes. X-ray scattering suggests dose-dependent amorphization in e-beam irradiated ZIF-8 and XPS indicates that formation of N-H bonds may contribute to the improved selectivity for CO2.