Researchers can now analyze how reactions proceed inside porous nanoparticles where the molecules are in such narrow channels that they cannot pass each other. Catalysis within these confined conditions is significantly impacted by restricted transport. Typical pore diameters are in the range of 2 - 10 nm, and with catalyst molecules attached inside them, the pore diameter can be reduced below 2 nm. Traditional computational tools do not capture the evolution of concentrations inside pores so narrow that reactants and products cannot pass each other. The new methods precisely describe this kind of constrained chemical diffusion. Narrow pores with catalytic sites varying in number and location were analyzed. Snapshots of the locations of reactants and products as a function of time show the factors that influence the transient and steady-state behaviors.These studies set the stage for understanding more complex systems and designing new, even better, catalysts.
Catalytic Conversion Reactions mediated by Single-file Diffusion in Linear Nanopores: Hydrodynamic versus Stochastic Behavior