Simultaneous Capture of N₂O and CO₂ from a N₂O/N₂/CO₂/O₂ Mixture with a Ni(II)-Pyrazolecarboxylate Framework

Nitrous oxide (N₂O) is a potent greenhouse gas and a major contributor to ozone depletion. Its primary industrial emission source is tail gas from adipic acid production, which typically comprises a mixture of N₂O, CO₂, N₂, and O₂. Current technologies for the removal of N₂O and CO₂ from tail gas are energy-intensive and operationally complex. Herein, for the first time, simultaneous capture of N₂O and CO₂ from the quaternary mixture is achieved using a Ni(II)-pyrazolecarboxylate framework, BUT-167. This material demonstrated an exceptional adsorption capacity (135.8 cm³ cm^-3 at 40 kPa) and a high packing density (790 mg cm^-3) for N₂O, outperforming reported sorbents. Moreover, BUT-167 also exhibits a remarkable CO₂ adsorption capacity (101.5 cm³ cm^-3 at 4 kPa), achieving simultaneously high selectivity values of 257.6 for CO₂/N₂ (4:96, v/v) and 135.7 for N₂O/N₂ (40/60). Importantly, BUT-167 exhibits robust and outstanding dual-gas removal performance across multiple adsorption-desorption breakthrough cycles under both dry and humid conditions. The strong affinity toward CO₂ and N₂O could be attributed to multiple hydrogen bonding interactions facilitated by its highly confined channel structure, as confirmed through single-crystal X-ray diffraction analysis.