Introducing Hydrogen-Bonding Microenvironment in Close Proximity to Single-Atom Sites for Boosting Photocatalytic Hydrogen Production

Inspired by enzymatic catalysis, it is crucial to construct hydrogen-bonding-rich microenvironment around catalytic sites; unfortunately, its precise construction and understanding how the distance between such microenvironment and catalytic sites affects the catalysis remain significantly challenging. In this work, a series of metal-organic framework (MOF)-based single-atom Ru₁ catalysts, namely, Ru₁/UiO-67-X (X = -H, -m-(NH₂)₂, -o-(NH₂)₂), have been synthesized, where the distance between the hydrogen-bonding microenvironment and Ru₁ sites is modulated by altering the location of amino groups. The -NH₂ group can form hydrogen bonds with H₂O, constituting a unique microenvironment that causes an increased water concentration around the Ru₁ sites. Remarkably, Ru₁/UiO-67-o-(NH₂)₂ displays a superior photocatalytic hydrogen production rate, ∼4.6 and ∼146.6 times of Ru₁/UiO-67-m-(NH₂)₂ and Ru₁/UiO-67, respectively. Both experimental and computational results suggest that the close proximity of amino groups to the Ru₁ sites in Ru₁/UiO-67-o-(NH₂)₂ improves charge transfer and H₂O dissociation, accounting for the promoted photocatalytic hydrogen production.