Design of dual-ligand coordination in metal organic frameworks for breaking the seesaw effect between de-NOx activity and N2 selectivity

Abstract

In the selective catalytic reduction (SCR) of NOx with NH3, a catalyst usually exhibits a seesaw effect on de-NOx activity and N2 selectivity at low temperatures. Herein, we designed metal-organic frameworks (MOFs) with dual-ligand coordination to regulate the electronic and morphological structure for a breakthrough of the seesaw effect. The developed catalyst attained a noteworthy NOx conversion exceeding 90% within 60–330 ℃ with increased N2 selectivity. The dual-ligand coordination leads to more defects and a more uniform electron distribution for delocalization of electrons, thereby improving de-NOx activity. Furthermore, the dual-ligand coordination manifests a Si-O-Mn bond for amplifying both de-NOx activity and thermal stability. Additionally, the dual ligands and Mn produce a hollow sea-urchin-like morphology with more exposed active sites for concentrating reactants and intermediates to improve electron transfer efficiency in N2 selectivity. This work clarifies the mechanism of dual-ligand regulation for electron-morphology to simultaneously enhance de-NOx activity and N2 selectivity.