A [Cu<sub>2</sub>O<sub>2</sub>]<sup>2+</sup> Core in Cu/ZSM-5 for Efficient Selective Catalytic Oxidation of Nitrogen-Containing VOCs and NH<sub>3</sub>
Ting Zhao, Xiaoxiao Duan, Ben Niu, Ganggang Li, Bing Zhang, Jing Zhang, Zhongshen Zhang, Jie Cheng, Zhengping Hao
Abstract
Highly efficient elimination of nitrogen-containing volatile organic compounds (NVOCs) or NH 3 via selective catalytic oxidation (SCO) while avoiding NO x is a strongly desired process for their control. However, limited by a lack of fundamental guidance such as accurate active site and reaction mechanisms, the targeted design of high-performance catalysts faces severe challenges. Herein, ZSM-5 zeolites supported by different copper species were used in the SCO of dimethylformamide (DMF) and NH 3 . Optimal 8% Cu/ZSM-5 had the highest N 2 selectivity of above 94%. Various in situ spectroscopic characterizations and DFT theoretical calculations precisely identified that the active site is a μ-(η 2:η 2 )-peroxo dicopper (bent; [Cu 2 O 2 ] 2+ ) core, which is associated with two Al sites separated by three SiO 4 tetrahedra units in the 10-membered ring of ZSM-5. The dynamic catalytic behavior of DMF-SCO was revealed to be that [Cu 2 O 2 ] 2+ transformed into mono-(μ-oxo) dicopper upon DMF adsorption, while the opposite process occurred when O 2 attacked. In situ DRIFTS elucidated the DMF-SCO reaction pathway and indicated that the disassociating N–H bond was the rate-determining step in transforming DMF to N 2 . This work not only strongly points the way to the design of high-performance catalysts of NVOCs and NH 3 elimination but provides methodological implications for in situ study of active sites and their dynamic structures.