CeCoOx-MNS catalyst derived from three-dimensional mesh nanosheet Co-based metal–organic frameworks for highly efficient catalytic combustion of VOCs

Abstract

Various three-dimensional (3D) Co-based metal organic frameworks (Co-MOFs) are successfully synthesized through modulation and reconstruction of secondary building units (SBU) with Co ions, including three-dimensional nanocube Co-MOFs (Co-MOFs-NC), three-dimensional mesh nanosheets Co-MOFs (Co-MOFs-MNS) and three-dimensional prismatic nanotube Co-MOFs (Co-MOFs-PNT). Specifically, mesh nanosheets Co-MOFs-MNS and prismatic nanotube Co-MOFs-PNT are synthesized for the first time through a post-processing strategy of nanocubic Co-MOFs-NC. It is discovered that the CeCoOx-MNS catalyst derived from Co-MOFs-MNS precursor following wet impregnation of cerium ions exhibits a superior activity for the complete oxidation of benzene, toluene and δ-xylene. Through a series of characterizations, it is verified that the CeCoOx-MNS catalyst owns more Co3+ and Ce3+ species, excellent redox performance (Ce4++Co2+→Ce3++Co3+), and abundant surface weak acid sites, which promote jointly the conversion of VOCs at a lower temperature. More importantly, in situ DRIFTS results over CeCoOx catalyst verify that the alkoxide, benzoate and anhydride species are the main intermediates, indicating that reaction pathway is likely to be as follows: adsorbed toluene → benzyl alcohol → benzoate → anhydride → acetate→ …→ CO2 and H2O.