Ligand-Shell Cooperativity in a Bilayer Silica-Sandwiched Mixed-Metals Nanocatalyst Design for Absolute Selectivity Switch

Abstract

Unlike homogeneous metal complexes, achieving absolute control over reaction selectivity in heterogeneous catalysts remains a formidable challenge due to the unguided molecular adsorption/desorption on metal-surface sites. Conventional organic surface modifiers or ligands and rigid inorganic and metal-organic porous shells are not fully effective. Here, we introduce the concept of "ligand-porous shell cooperativity" to desirably switch reaction selectivity in heterogeneous catalysis. We present a nanocatalyst design strategy consisting of bilayer silica-sandwiched 2D mixed metal islands. The intimate 2D/2D nanoscale interfacing between porous silica layers and flat island-like mixed-metal sites, combined with organic ligands, creates a nanoconfined microenvironment that enables reliable control of molecular orientation-dependent reactivity, affording the desired product in 100% selectivity. This design simultaneously leverages the hydrophobicity and flexibility of organic ligands and the nanoscale geometric rigidity of the pores inside the inorganic silica shell. Our strategy is effective with simple amorphous silica, random Cu-alloy, and commonly used metal-coordinating ligands. We demonstrate the applicability in industrially significant reactions: selective hydrogenation of alkynes, alpha,beta-unsaturated esters/aldehydes, and nitroarenes. Our findings offer the valuable scope of a multicomponent compact nanoscale design strategy in next-generation switchable, sustainable, and recyclable catalysis.