Engineering Single-Atom Sites into Pore-Confined Nanospaces of Porphyrinic Metal–Organic Frameworks for the Highly Efficient Photocatalytic Hydrogen Evolution Reaction

As a type of heterogeneous catalyst expected for the
maximum atom
efficiency, a series of single-atom catalysts (SACs) containing spatially
isolated metal single atoms (M-SAs) have been successfully prepared
by confining M-SAs in the pore-nanospaces of porphyrinic metal–organic
frameworks (MOFs). The prepared MOF composites of M-SAs@Pd-PCN-222-NH2 (M = Pt, Ir, Au, and Ru) display exceptionally high and persistent
efficiency in the photocatalytic hydrogen evolution reaction with
a turnover number (TON) of up to 21713 in 32 h and a beginning/lasting
turnover frequency (TOF) larger than 1200/600 h–1 based on M-SAs under visible light irradiation (λ ≥
420 nm). The photo-/electrochemical property studies and density functional
theory calculations disclose that the close proximity of the catalytically
active Pt-SAs to the Pd–porphyrin photosensitizers with the
confinement and stabilization effect by chemical binding could accelerate
electron–hole separation and charge transfer in pore-nanospaces,
thus promoting the catalytic H2 evolution reaction with
lasting effectiveness.