Developing Insoluble Polyoxometalate Clusters to Bridge Homogeneous and Heterogeneous Water Oxidation Photocatalysis

Abstract

Cluster catalysts are attractive for their atomically precise structures, defined compositions, tunable coordination environments, uniform active sites, and their ability to transfer multiple electrons, but they suffer from poor stability and recyclability. Here, we report a general approach to the direct insolubilization of a water soluble polyoxometalate (POM) [{(B‐α‐PW9O34)Co3(OH)(H2O)2(O3PC(O)‐(C3H6NH3)PO3)}2Co]14− (Co7) and formation of a series of POM‐based solid catalysts with the counter‐cations Ag+, Cs+, Sr2+, Ba2+, Pb2+, Y3+, and Ce3+. They exhibit improved catalytic activities for visible‐light‐driven water oxidation following the trend CsCo7>SrCo7>AgCo7>CeIIICo7>BaCo7>YCo7>PbCo7. While CsCo7 exhibits mainly homogeneous catalysis, the others are predominantly heterogeneous catalysts. An optimal oxygen yield of 41.3 % and a high apparent quantum yield (AQY) of 30.6 % for SrCo7 is obtained, which is comparable to that of the parent homogeneous POM. Band gap structures, UV/Vis spectra, and real‐time laser flash photolysis experiments collectively suggest that easier electron transfer from the solid POM catalyst to the photosensitizer promotes photocatalytic water oxidation performance. These solid POM catalysts exhibit good stability, which is directly confirmed by a combination of Fourier‐transform infrared spectroscopy, electron microscopy, X‐ray diffraction patterns, Raman spectroscopy, X‐ray photoelectron spectroscopy, five cycles of tests, and poisoning experiments.

A sandwiched Co4-added polyoxometalate for efficient visible light-driven hydrogen evolution

“…12,22 Up to now, a large number of TMAPs have been applied in the study of water reduction catalysts (WRCs). 23–30 Co-added POMs are applied to photocatalytic water splitting reactions with excellent reactivity, 31 and the fragment {XW 9 O 34 } can induce Co 2+ , thereby improving the performance of Co-added POMs (CoAPs) as catalytically active centers for H 2 evolution driven by visible light.…”

Role of Metal–Organic Framework Topology on Thermodynamics of Polyoxometalate Encapsulation

“…Polyoxometalates (POMs) are discrete anionic metal-oxo clusters whose rich redox properties and high availability of active sites afford them strong oxidizing potential. − They have been used as acids, , photocatalysts, , and oxidizing agents − for the transformation of commodity chemicals in a variety of different sectors. However, their tendency to aggregate in solution greatly reduces the availability of catalytic active sites .…”

Recent research progress of selenotungstate-based biomolecular sensing materials

“…Polyoxometalates (POMs) are a distinguished class of metal–oxo anionic clusters assembled from early transition-metal centers and oxygen bridges, 23–27 which can provide a diverse array of versatile inorganic building blocks for constructing multi-functional materials with remarkable properties in optics, catalysis, sensing, magnetism, and biomedicine. 23–27 On the one hand, POMs have strong electron affinity and remarkable multi-electron redox properties, so they could become materials for constructing electrochemical sensors.…”