Achieving "True" Selective Hydrogenation by CO Treatment of the Pt/TiO2 Catalyst.

Selective hydrogenation represents a fundamental chemical transformation in industrial catalysis, yet achieving high selectivity remains a formidable challenge, particularly toward the conversion of less reactive functional groups over more reactive ones. Current approaches often rely on a preferential manner, requiring precise reaction control to prevent complete substrate conversion, which limits the operational flexibility and complicates product separation. Here, we demonstrate that a Pt/TiO₂ catalyst, when subjected to a simple CO gas thermal treatment, can enable the true selective hydrogenation of the thermally less reactive -NO₂ group while preserving the more reactive -C═C bond. Mechanistic studies reveal that the treated catalyst features two distinct active sites: single-atom Pt sites that facilitate -C═C bond hydrogenation through rapid, reversible hydrogen insertion and elimination, giving rise to an apparent nonactivity, and TiO_x and C-encapsulated Pt nanoparticles that provide selective permeability for the -NO₂ group. The discovery offers a robust solution to the challenges of selective hydrogenation, presenting a versatile strategy for the design and preparation of highly selective catalytic systems with significant implications for industrial applications.