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.

中文翻译：

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将单原子位点设计成卟啉金属-有机骨架的孔隙限制纳米空间，用于高效光催化析氢反应

作为一种预期具有最大原子效率的多相催化剂，通过将 M-SAs 限制在卟啉的孔纳米空间中，成功制备了一系列包含空间隔离金属单原子 (M-SAs) 的单原子催化剂 (SACs)金属有机骨架 (MOF)。制备的 M-SAs@Pd-PCN-222-NH ₂ (M = Pt、Ir、Au 和 Ru) MOF 复合材料在光催化析氢反应中表现出异常高和持久的效率，周转数 (TON) 高达32 小时内达到 21713，开始/持续周转频率 (TOF) 大于 1200/600 小时^–1基于可见光照射下的 M-SAs (λ ≥ 420 nm)。光/电化学性质研究和密度泛函理论计算表明，具有催化活性的 Pt-SAs 与具有化学结合限制和稳定作用的 Pd-卟啉光敏剂非常接近，可以加速电子-空穴分离和孔中的电荷转移-纳米空间，从而促进具有持久有效性的催化H _{2析出反应。}