Rational reconstruction from attapulgite to MCM-41 and its superior application in formaldehyde degradation

Abstract

The inferior reactive metal dispersion caused by a lack of structural defects limits the application of MCM-41 in synthesizing effective catalysts. Herein, we substituted a conventional silicon source (TEOS) with attapulgite to fabricate structural defects on MCM-41. Catalytic performance evaluation results after Ag incorporation proved that this substitution favored HCHO degradation. It was observed that owing to their high structural stability, attapulgite rods only merged with each other during MCM-41 construction, which resulted in a sheet-like morphology without the formation of any mesoporous structure. Notably, the metal species (Al, Mg and Fe) in attapulgite improved the dispersion and size distribution of Ag nanoparticles and intensified the electronic properties of Ag species. As for MCM-41 prepared with acidified attapulgite, demetallization resulted in the exposure of Si–O⁻ groups and a decrease in structural stability. In subsequent MCM-41 construction, acidified attapulgite collapsed into colloidal particles and debris. Further, the colloidal particles were drawn together by CTA⁺, leading to the formation of chrysalis-like particles with regular mesopores, and debris that surrounded CTA⁺ collapsed, forming cotton-like morphology with irregular mesopores. Notably, the reservation of Si–O⁻ groups after MCM-41 construction could enhance the exposure of oxygen species and the dispersion of Ag nanoparticles on the outer surface and inner mesopores. Moreover, such Si–O⁻ groups are adsorptive and reactive towards HCHO.