Fabrication and Characteristics of Mn@ Cu₃(BTC)₂ for Low-Temperature Catalytic Reduction of NO_x with NH₃

Abstract

Novel catalysts with high activity for the selective catalytic reduction of NO with NH3 (NH3-SCR) at low temperatures are highly demanded. In this study, mixed-node metal-organic frameworks (MOFs), e.g. Mn@CuBTC with controlled Mn composition in Cu3(BTC)2, were fabricated using postsynthetic exchange method and their structural characteristics and catalytic performances for NH3-SCR reaction were assessed. A series of analyses in terms of structure, surface morphology, texture, and chemical state determined that Mn ions were successfully incorporated into the Cu3(BTC)2 crystal lattice as well as adsorbed on the walls of nanopores in the framework. The pore sizes can be finely tuned in the presence of Mn ions in the cages, which significantly suppressed water adsorption. The NH3-SCR activity of Mn@CuBTC exhibited nearly 100% NOx conversion rate in the temperature range (230–260°C). The superior NH3-SCR performance is attributed to the proper pore sizes, reduced water content, and the synergistic effect between manganese and copper ions in the MOF structure, which enhanced NH3 bound to the active Lewis sites.

Perspectives in Adsorptive and Catalytic Mitigations of NOx Using Metal–Organic Frameworks

“…DRIFTS experiments were performed showing that NH 3 is adsorbed on Lewis sites, and no peaks corresponding to NO were observed. The authors suggest that the combination of proper pore sizes, enhancement of redox activity via incorporation of Mn 4+ ions, and the synergistic effect between Mn 2+ and Cu 2+ results in superior DeNO x performance . The commercial HKUST-1 (Basolite C300) was examined under NH 3 -SCR conditions in the studies of Świrk et al , During the pretreatment step carried out in helium from 145 to 250 °C, the authors observed a gradually increasing formation of carbon dioxide with a heating ramp, highlighting the crucial role of the temperature.…”

“…The authors suggest that the combination of proper pore sizes, enhancement of redox activity via incorporation of Mn 4+ ions, and the synergistic effect between Mn 2+ and Cu 2+ results in superior DeNO x performance. 114 The commercial HKUST-1 (Basolite C300) was examined under NH 3 -SCR conditions in the studies of S ́wirk et al 115,116 During the pretreatment step carried out in helium from 145 to 250 °C, the authors observed a gradually increasing formation of carbon dioxide with a heating ramp, highlighting the crucial role of the temperature. The temperature of 185 °C is recognized as the highest possible and carbon-free experimental adjustment, allowing the authors to prevent a partial decomposition of the organic framework.…”

Progress in Metal-Organic Framework Catalysts for Selective Catalytic Reduction of NOx: A Mini-Review

“…Ion exchange is one of the most effective methods for synthesizing bimetallic MOFs. Yao et al first synthesized Cu-MOF and then incorporated Mn ions into the Cu-MOF through ion exchange in order to obtain Mn/Cu-BTC (BTC = 1,3,5-benzenetricarboxylic acid) [23]. The introduction of Mn changed the pore size of the Cu-MOF, and the synergistic effects of Mn and Cu enhanced its redox activity.…”

DeNOx of Nano-Catalyst of Selective Catalytic Reduction Using Active Carbon Loading MnOx-Cu at Low Temperature

“…Therefore, the increased acidic sites might represent one of the most important reasons for the higher catalytic activity of the MnO x -Cu/AC catalyst. Yao et al found that the synergistic effects between Mn and Cu ions could further enhance the low-temperature performances via modified active sites [48]. Moreover, Shu et al found that surface acidity played a critical role in the SCR reaction [49].…”