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 Ru 1 catalysts, namely, Ru 1 /UiO-67-X (X = -H, - m -(NH 2 ) 2 , - o -(NH 2 ) 2 ), have been synthesized, where the distance between the hydrogen-bonding microenvironment and Ru 1 sites is modulated by altering the location of amino groups. The -NH 2 group can form hydrogen bonds with H 2 O, constituting a unique microenvironment that causes an increased water concentration around the Ru 1 sites. Remarkably, Ru 1 /UiO-67- o -(NH 2 ) 2 displays a superior photocatalytic hydrogen production rate, ∼4.6 and ∼146.6 times of Ru 1 /UiO-67- m -(NH 2 ) 2 and Ru 1 /UiO-67, respectively. Both experimental and computational results suggest that the close proximity of amino groups to the Ru 1 sites in Ru 1 /UiO-67- o -(NH 2 ) 2 improves charge transfer and H 2 O dissociation, accounting for the promoted photocatalytic hydrogen production.