A Direct Z‐Scheme Quasi‐2D/2D Heterojunction Constructed by Loading Photosensitive Metal–Organic Nanorings with Pd Single Atoms on Graphitic–C3N4 for Superior Visible Light‐Driven H2 Production

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‐C3N4 with Pd single atoms. The optimized 3.5% MAC‐1/g‐C3N4 single‐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 H2 production. The H2 yield rate of 22.3 mmol g−1 h−1 and the corresponding turnover number based on Pd or MAC‐1 amount (TONPd/TONMAC‐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‐C3N4 nanosheets therefore has great potential as an efficient and sustainable photocatalyst for solar‐driven H2 production. A direct Z‐scheme quasi‐2D/2D heterojunction MAC‐1/g‐C3N4 formed by loading photosensitive metal–organic nanorings with Pd single atoms on g‐C3N4 exhibits an impressive visible light‐driven hydrogen production activity and good stability. This study presents an inspiration for novel light‐to‐fuel conversion system involving the combination of 2D/2D composite materials as well as Z‐scheme heterojunction for solar‐driven water splitting.