Temperature-Dependent Nitrous Oxide/Carbon Dioxide Preferential Adsorption in a Thiazolium-Functionalized NU-1000 Metal-Organic Framework.

Solvent-assisted ligand incorporation (SALI) of the ditopic linker 5-carboxy-3-(4-carboxybenzyl)thiazolium bromide [()Br] into the zirconium metal-organic framework [ZrO(OH)(HO)(TBAPy), where NU = Northwestern University and HTBAPy = 1,3,6,8-tetrakis(-benzoic-acid)pyrene], led to the SALIed material of minimal formula [ZrO(OH)(HO)(TBAPy)()]Br. has been thoroughly characterized in the solid state. As confirmed by powder X-ray diffraction, this material keeps the same three-dimensional architecture of and the dicarboxylic extra linker bridges adjacent [Zr] nodes 8 Å far apart along the crystallographic -axis. The functionalized MOF has a BET specific surface area of 1560 m/g, and it is featured by a slightly higher thermal stability than its parent material ( = 820 vs. 800 K, respectively). has been exploited for the capture and separation of two pollutant gases: carbon dioxide (CO) and nitrous oxide (NO). The high thermodynamic affinity for both gases [isosteric heat of adsorption () = 25 and 27 kJ mol for CO and NO, respectively] reasonably stems from the strong interactions between these (polar) "stick-like" molecules and the ionic framework. Intriguingly, shows an unprecedented temperature-dependent adsorption capacity, loading more NO in the 298 K ≤ ≤ 313 K range but more CO at temperatures falling out of this range. Grand canonical Monte Carlo simulations of the adsorption isotherms confirmed that the preferential adsorption sites of both gases are the triangular channels (micropores) in close proximity to the polar pillar. While CO interacts with the thiazolium ring in an "end-on" fashion through its O atoms, NO adopts a "side-on" configuration through its three atoms simultaneously. These findings open new horizons in the discovery of functional materials that may discriminate between polluting gases through selective adsorption at different temperatures.