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 ¹³C 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 H₂, as CO and N₂.