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 ] ( Ce_TzTz ) and [Ce 6 O 4 (OH) 4 ( TzTz ) 4 ( PyPy ) 2 ] ( Ce_TzTz_PyPy ; 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. Ce_TzTz 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, Ce_TzTz_PyPy 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@ Ce_TzTz ] and [CO 2 @ Ce_TzTz_PyPy ] 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.