One-pot synthesis of flower-like sulfated Si-doped Cu@SZN-2Si solid acid for the selective catalytic oxidation of triethylamine

A novel Cu@SZN-2Si catalyst with both microporous and mesoporous structures was successfully fabricated using a new template agent (BCph-10-6-6). This catalyst showed outstanding catalytic performance in the selective catalytic oxidation (SCO) of triethylamine (TEA). Notably, in contrast to the conventional mesoporous Cu@SZ-2Si_CTAB synthesised with CTAB, Cu@SZN-2Si presented a flower-like nanosheet morphology. It boasted a higher density of Lewis acid sites and more surface-adsorbed oxygen (O ads ). Under the reaction conditions at 280 °C, the TEA conversion reached 100 %, and the N 2 yield was as high as 99.2 %. Moreover, in the presence of 10.0 vol% H 2 O vapour, the catalytic activity of Cu@SZN-2Si remained above 87.3 % at 280 °C and maintained stable operation for 130 h at 400 °C. Structural analysis coupled with DFT calculations revealed that Si incorporation enabled the crystallization of tetragonal ZrO 2 in the presence of SO 4 2− ions, while forming an amorphous SiO 2 that encapsulated the ZrO 2 surface. This structural characteristic significantly increased the number of isolated Cu 2+ species and acidic sites on the catalyst surface. The strong interaction between these isolated Cu 2+ species and acidic sites was crucial for promoting the adsorption and activation of TEA. In addition, in-situ DRIFTs results indicated that TEA first adsorbed on the Cu@SZN-2Si surface, followed by a thermal decomposition process. The cleavage of the C-N bond in TEA generated NH* intermediates, which were essential for N 2 generation and promoted the SCO of TEA.