Molecule-well in platinum-zeolite engineers molecular adsorption for highly selective hydrogenation.

Metal-zeolite composites have emerged as a promising class of heterogeneous catalysts, while the atomic-level understanding of their internal microenvironments remains limited. Here, we integrate controlled synthesis, catalytic evaluation, and atomistic modeling to resolve and quantify the three-dimensional (3D) microenvironments formed by platinum encapsulated within MFI zeolites. Using unsaturated aldehyde hydrogenation as a model reaction, we identify two distinct access modes-channel-access and well-access-that govern how reactant molecules approach Pt active sites. In particular, the well-access configuration forms a molecule-well that imposes steric constraints favoring C=O bond adsorption, thereby enabling highly selective hydrogenation to unsaturated alcohol. These findings establish a direct structure-function relationship between the geometry of the zeolite-confined space and catalytic performance, offering a molecular-level framework for rational catalyst design.