Zirconium–Porphyrin‐Based Metal–Organic Framework Hollow Nanotubes for Immobilization of Noble‐Metal Single Atoms

Abstract

Single atoms immobilized on metal–organic frameworks (MOFs) with unique nanostructures have drawn tremendous attention in the application of catalysis but remain a great challenge. Various single noble‐metal atoms have now been successfully anchored on the well‐defined anchoring sites of the zirconium porphyrin MOF hollow nanotubes, which are probed by aberration‐corrected scanning transmission electron microscopy and synchrotron‐radiation‐based X‐ray absorption fine‐structure spectroscopy. Owing to the hollow structure and excellent photoelectrochemical performance, the HNTM‐Ir/Pt exhibits outstanding catalytic activity in the visible‐light photocatalytic H2 evolution via water splitting. The single atom immobilized on MOFs with hollow structures are expected to pave the way to expand the potential applications of MOFs.

The Multifaceted Reactivity of Single‐Atom Heterogeneous Catalysts

“…[10] Aided by synthetic and analytical advancements,ahuge range of potential host materials has now been reported (Figure 2), which encompasses metal oxides, [11][12][13][14] metal hydroxides, [15,16] metals (also termed single-atom alloys (SAAs)), [17,18] micro/ mesoporous materials such as zeolites, [19,20] metal-organic frameworks (MOFs), [21,22] silicas, [23,24] carbon-based materials, [25][26][27][28] organopolymers, [29,30] nitrides, [31][32][33] and carbides. [10] Aided by synthetic and analytical advancements,ahuge range of potential host materials has now been reported (Figure 2), which encompasses metal oxides, [11][12][13][14] metal hydroxides, [15,16] metals (also termed single-atom alloys (SAAs)), [17,18] micro/ mesoporous materials such as zeolites, [19,20] metal-organic frameworks (MOFs), [21,22] silicas, [23,24] carbon-based materials, [25][26][27]…”

Single Metal Atom Photocatalysis

“…As one of the most important functional porous materials, MOFs have also been chosen as support for anchoring single metal atoms . For example, by using zirconium–porphyrinic MOF hollow nanotubes (HNTM) as support, various single noble metal atoms, such as Pt and Ir, have been atomically dispersed and successfully anchored on the well‐defined square‐planar porphyrin units of HNTM, as confirmed by aberration‐corrected scanning transmission electron microscopy . Further synchrotron‐radiation‐based X‐ray absorption fine‐structure spectroscopy revealed that the Pt atoms were anchored in the center of porphyrin structures and bonded with nitrogen atoms, creating the Pt–N 4 porphyrin plane as active sites for photocatalytic H 2 evolution.…”

“…Further synchrotron‐radiation‐based X‐ray absorption fine‐structure spectroscopy revealed that the Pt atoms were anchored in the center of porphyrin structures and bonded with nitrogen atoms, creating the Pt–N 4 porphyrin plane as active sites for photocatalytic H 2 evolution. In addition, two chlorine atoms coordinated with one Pt atom in perpendicular to the Pt–N 4 porphyrin plane . The authors believed that the excellent photocatalytic H 2 activity came from the single‐atom feature, unique hollow structure, fast mass diffusion, improved separation of charge carriers, and the reduced charge‐transfer resistance .…”

“…In addition, two chlorine atoms coordinated with one Pt atom in perpendicular to the Pt–N 4 porphyrin plane . The authors believed that the excellent photocatalytic H 2 activity came from the single‐atom feature, unique hollow structure, fast mass diffusion, improved separation of charge carriers, and the reduced charge‐transfer resistance . Fang et al successfully confined single Pt atoms into a highly stable aluminum‐based porphyrinic MOF ((AlOH) 2 H 2 TCPP (H 2 TCPP = 4,4′,4″,4′″‐(porphyrin‐5,10,15,20‐tetrayl)tetrabenzoate), donated as Al‐TCPP).…”

Nitrogen‐Doped Porous Carbon Supported Nonprecious Metal Single‐Atom Electrocatalysts: from Synthesis to Application

“…In general, the X‐ray absorption fine structure can detect the coordination environment of the target atom to distinguish whether it is single atom states or cluster states, and at the same time characterize the interaction between the target atom and the support, which is indispensable for the structure characterization of the metal single atom . As shown in Figure , Wei et al used the in situ synchrotron radiation XAFS combined with theoretical calculations to identify for the first time the true active site structure of the Co single atom catalyst in the alkaline hydrogen evolution reaction .…”