CO2 Adsorption Sites in UTSA-16: Multitechnique Approach

The key role of K+ counterions in determining the high CO2 capacity of UTSA-16 has been highlighted thanks to a combined use of in situ infrared and C-13 solid-state NMR spectroscopies performed in a controlled atmosphere at variable temperature and pressure. A second family of sites, engaged at higher temperature or at higher coverage, was identified in the organic linker. Variable temperature IR measurements of molecular hydrogen at 15 K allowed to further distinguish the K+ sites in two families, slightly different in their polarizing ability and indistinguishable on the basis of CO2 isosteric heat and by using a less sensitive probe than H-2, as CO and N-2.