Engineering of Highly Dispersed [Cu(OH)] + Sites in Diverse Porous Aluminosilicates via Size-Selective Atomic Layer Deposition for Enhanced NH3-Selective Catalytic Oxidation Behaviors

Abstract

The fabrication of highly uniform and dispersed catalysts is achievable through atomic layer deposition (ALD). However, the application of this method in porous materials is largely restricted by the size compatibility between the host and the guest molecules. In this study, we coupled ALD with different Cu-based catalysts to develop an interfacial engineering strategy for the selective catalytic oxidation of ammonia (NH3–SCO). Using Cu(hfac)2 as the precursor, it was demonstrated that the pore structure served as a critical steric gatekeeper. Unhindered mass transfer pathway was observed in mesoporous Al-SBA-15, which successfully accommodated the large precursors. This led to a high copper loading of 1.58 wt % along with high interfacial dispersion. On the contrary, the narrow pores of microporous zeolites caused significant pore-mouth blockage and external accumulation because of the size exclusion effect. Therefore, superior intrinsic catalytic activity was found in the Cu-Al-SBA-15, realizing complete NH3 conversion at 350 °C combined with excellent N2 selectivity. Comprehensive characterizations indicated that a large proportion (75.64%) of active mononuclear [Cu(OH)]+ species was stabilized by the abundant mesopores and numerous anchoring sites. These findings provide fundamental information regarding the size-exclusion mechanisms in ALD, suggesting a potential material design to precisely control metal–support interfaces for catalysis.