A Direct Z‐Scheme Quasi‐2D/2D Heterojunction Constructed by Loading Photosensitive Metal–Organic Nanorings with Pd Single Atoms on Graphitic–C₃N₄for Superior Visible Light‐Driven H₂Production

Rational design of Z‐scheme composite photocatalysts with 2D/2D heterojunction is a promising method to convert solar energy into chemical fuels. Herein, a Pd₂L₂‐type metal–organic nanoring (MAC‐1), which can serve as a photochemical molecular device (PMD), is assembled by catalytic Pd²⁺centers and photosensitive ligands (M‐7). Then MAC‐1 is combined with graphite‐phase carbon nitride (g‐C₃N₄) to construct a direct Z‐scheme quasi‐2D/2D composite material MAC‐1/g‐C₃N₄with Pd single atoms. The optimized 3.5% MAC‐1/g‐C₃N₄single‐atom catalyst (SAC) shows better photocatalytic performance than g‐C₃N₄, MAC‐1, Pd/g‐C₃N₄, M‐7/Pd/g‐C₃N₄, and 3.5% MAC‐1/g‐C₃N₄‐mixed and also displays good durability for H₂production. The H₂yield rate of 22.3 mmol g⁻¹ h⁻¹and the corresponding turnover number based on Pd or MAC‐1 amount (TON_Pd/TON_MAC‐1) of 119 172/238 344 within 50 h are achieved for 3.5% MAC‐1/g‐C₃N₄, which is one of the highest records of all visible light‐driven g‐C₃N₄‐based photocatalysts reported. Such remarkably enhanced activity can result from the enhanced charge carrier mobility, improved light absorption ability, enlarged heterojunction contact interface, and highly monodispersed Pd active sites. The Z‐scheme SAC composed of metal–organic nanorings and g‐C₃N₄nanosheets therefore has great potential as an efficient and sustainable photocatalyst for solar‐driven H₂production.