Selective Carbon Dioxide versus Nitrous Oxide Adsorption in Cerium(IV) Bithiazole and Bipyridyl Metal‐Organic Frameworks

Abstract The two Ce IV MOFs Ce 6 O 4 (OH) 4 (TzTz) 6 (CeTzTz) and Ce 6 O 4 (OH) 4 (TzTz) 4 (PyPy) 2 (CeTzTzPyPy ; H 2 TzTz = 2, 2′‐bithiazole‐5, 5′‐dicarboxylic acid, H 2 PyPy = 2, 2′‐bipyridine‐5, 5′‐dicarboxylic acid) are prepared starting from a pre‐formed Ce 6 glycinate‐capped cluster. N 2 isotherms collected at 77 K revealed BET specific surface areas of 1136 and 238 m 2 g −1, respectively. Their CO 2 and N 2 O adsorption capacity is assessed at T = 273 and 298 K and p = 1 bar. CeTzTz shows the highest gas uptake (7. 9 and 9. 7 wt% at 298 K and 11. 5 and 12. 5 wt% at 273 K for CO 2 and N 2 O, respectively). More interestingly, this homo‐linker MOF possesses a higher capacity, thermodynamic affinity (Q st) CO2 = 18. 2 kJ mol −1 vs (Q st) N2O = 25. 4 kJ mol −1 and selectivity (IAST S N2O/CO2 = 1. 6 at T = 273 K) toward N 2 O than the mixed‐linker sample. At variance, CeTzTzPyPy shows a slightly higher capacity, thermodinamic affinity (Q st) CO2 = 29. 5 kJ mol −1 vs (Q st) N2O = 26. 4 kJ mol −1 and selectivity (IAST S CO2/N2O = 1. 4 at T = 298 K) toward CO 2. DFT optimizations carried out on the N 2 O@ CeTzTz and CO 2 @ CeTzTzPyPy systems revealed that the primary adsorption sites are the cerium ions of the Ce6 metallic node for N2O and the thiazole N‐atoms on the TzTz linker for CO2, respectively.