Transition Metal Inserted Porphyrin Metal-Organic Frameworks as π-backbonding Adsorbents for NO2 Removal.

Mitigating ambient nitrogen dioxide (NO 2 ) pollution via selective adsorption on porous materials represents a promising approach to tackle such an increasingly pressing environmental health issue. However, very few porous adsorbents have sufficiently high NO 2 adsorption capacity and good regenerability simultaneously. Here we attempt to address this challenge by developing π-backbonding adsorbents in the transition metal (TM) incorporated porphyrin metal-organic frameworks (PMOFs). Breakthrough experiments show that PMOFs with inserted TMs achieve appreciable NO 2 capacity and good regenerability. Combined in-situ DRIFTS, synchrotron powder XRD, and DFT calculations reveal the adsorption mechanism - NO 2 partially transforms to N 2 O 4 and interacts with transition metal via π-backbonding and Al-node via hydrogen bonding. This work affords new insights for designing next-generation adsorbents for ambient NO 2 removal and presents PMOFs as a platform to tailor π-backbonding adsorbents.