Low-temperature selective catalytic reduction of NOx with NH3: Exploring the mechanism of enhancing H2O tolerance through methylation functionalization and structural regulation in IPAx-Mn-BTC

In the selective catalytic reduction (SCR) of NOx with NH3, it is crucial to design low-temperature de-nitrification (de-NOx) catalysts with high H2O tolerance. Here, we developed a type of low-temperature de-NOx catalyst (IPAx-Mn-BTC) with strong H2O tolerance through methyl functionalization. In the presence of the optimal catalyst (IPA50-Mn-BTC), the NOx conversion only decreased from 97% to 90% after introducing 6% H2O for 6 h at low temperature of 150 degrees C. The results of in-situ DRIFTS and density functional theory calculations confirm that the de-NOx reaction process and the generation of intermediate states that occur on the surface of the IPA50-Mn-BTC are not affected by H2O. The elimination of the small pore size (< 4.3 nm) and the diminished H2O adsorption energy resulted from methyl functionalization are the key factors behind the improved H2O tolerance. This work provides a new approach for designing low-temperature de-NOx catalysts with high H2O tolerance.