Probing the methanol heterogeneous photochemistry processes by operando NMR – The role of bulk water

Solid-liquid heterogeneous catalysis reactions play key roles in industrial catalytic reactions, throughout pollution control, fuel cell, methanol reforming and so on. But, few operando techniques have been performed to track the complex reaction processes, especially those in bulk liquid environment containing two or more liquid reactants, thus leaving a gap in our understanding of the reaction mechanisms deep into the working conditions. Here, we demonstrate an approach, using operando nuclear magnetic resonance (NMR) to probe the dynamics and kinetics of the methanol heterogeneous photochemistry processes in liquid condition with and without bulk water (H₂O). It shows that not only can bulk H₂O affect the types of methanol reforming products, but also its participation way can vary from H₂O molecule to H-atom. Furthermore, the productivities of the main products - methylene glycol (HOCH₂OH) and hemiacetal (CH₃OCH₂OH) – show different dependency on the H₂O concentration, which is further supported by the density functional theory calculations (DFT). The operando NMR method opens up exciting opportunities for the mechanism studies of heterogeneous catalysis reaction in bulk liquid.