Selective Carbon Dioxide versus Nitrous Oxide Adsorption in Cerium(IV) Bithiazole and Bipyridyl Metal‐Organic Frameworks
Matteo Pugliesi, Margherita Cavallo, Cesare Atzori, Beatrice Garetto, Elisa Borfecchia, Lorenzo Donà, Bartolomeo Civalleri, Giulia Tuci, Giuliano Giambastiani, Simona Galli, Francesca Bonino, Andrea Rossin
Abstract
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.