2.3. In-situ titrations
Titration experiments with NO (10 wt.% NO, balance N2, Matheson, Research Purity) and H2O (deionized, 18.3 MΩ) were conducted at 423 K under constant reaction conditions: 14.5 kPa N2O, 1.5 kPa CH4, t = 2 h. For NO titration experiments, NO was fed over MIL-100(Fe) prior to the introduction of CH4 and N2O due to the significant time it takes for NO to break through the MOF bed in comparison to the reactants (Section S2.6, SI). Under titrant co-feeds, inert carrier gas (He, Matheson, Ultra High Purity) concentrations were reduced to maintain constant reactant partial pressures. Total quantities of NO and H2O adsorbed by MIL-100 were estimated through breakthrough curves measured using an online mass spectrometer (MKS Cirrus 2) at the outlet of the bed. Molar flow rates were calibrated with respect to those of argon (internal standard) under the assumption that no argon was adsorbed by the sample.