Abstract
Here we report the use of a pillaring strategy for the design and synthesis of three novel amide-functionalized metal organic frameworks (MOFs), TMUs-22/-23/-24, isoreticular to the recently reported imine-functionalized TMU-6 and TMU-21 MOFs. An extensive study of their CO2 sorption properties and selectivity for CO2 over N-2, from single gas sorption isotherms to breakthrough measurements, revealed that not only the incorporation of amide groups but also their accessibility is crucial to obtain enhanced CO2 sorption and accessible amide groups CO2/N-2 selectivity. Therefore, the MOF with more accessible amide groups (TMU-24) shows a CO2/N-2 selectivity value of ca. 10 (as revealed by breakthrough experiments), which is ca. 500% and 700% of the selectivity values observed for the other amide-containing (TMU-22 and TMU-23) and imine-containing (TMU-6 and TMU-21) MOFs.