Self‐Assembly of a Phosphate‐Centered Polyoxo‐Titanium Cluster: Discovery of the Heteroatom Keggin Family

Abstract

Over the past 200 years, the most famous and important heteroatom Keggin architecture in polyoxometalates has only been synthesized with Mo, W, V, or Nb. Now, the self‐assembly of two phosphate (PO43−)‐centered polyoxo‐titanium clusters (PTCs) is presented, PTi16 and PTi12, which display classic heteroatom Keggin and its trivacant structures, respectively. Because TiIV has lower oxidate state and larger ionic radius than MoVI, WVI, VV, and NbV, additional TiIV centres in these PTCs are used to stabilize the resultant heteroatom Keggin structures, as demonstrated by the cooresponding theoretical calculation results. These photoactive PTCs can be utilized as efficient photocatalysts for highly selective CO2‐to‐HCOOH conversion. This new discovery indicates that the classic heteroatom Keggin family can be assembled with Ti, thus opening a research avenue for the development of PTC chemistry.

Polyoxometalate‐Based Compounds for Photo‐ and Electrocatalytic Applications

“…The Re is responsible for binding and activating CO 2 substrate,w hile the POM acts as photosensitizer,e lectron reservoir,a sw ell as electron donor.I n 2019, Lan group first reported two Ti IV 12 , CHA = cyclohexylammonium), both of which can be used as homogeneous photocatalysts for CO 2 RR. [26] These photoactive POMs can highly selective reduce CO 2 to HCOOH under ultraviolet irradiation (Figure 3). TheT i IV ions within POM structures are the catalytically active centers for CO 2 reduction, and the generation of Ti III during the photocatalytic process can be detected by electron spin resonance (ESR) measurements.T i 4+ ions in POMs were reduced into Ti 3+ by receiving photo-excited electrons transferred from O 2À ,w hile the corresponding photo-generated holes were quenched by sacrificial agent.…”

Polyoxometalate‐Based Compounds for Photo‐ and Electrocatalytic Applications

“…The Re is responsible for binding and activating CO 2 substrate, while the POM acts as photosensitizer, electron reservoir, as well as electron donor. In 2019, Lan group first reported two Ti IV ‐based heteroatom Keggin and its trivacant lacunary architectures, [Ti 16 (OH) 4 O 20 (PO 4 )(O i Pr) 16 ]⋅guests (PTi 16 , HO i Pr=isopropanol) and [Ti 12 O 15 (PO 4 )( i PrPO 4 ) 3 ‐(O i Pr) 12 ](CHA) 3 (H 2 O) (PTi 12 , CHA=cyclohexylammonium), both of which can be used as homogeneous photocatalysts for CO 2 RR [26] . These photoactive POMs can highly selective reduce CO 2 to HCOOH under ultraviolet irradiation (Figure 3).…”

Precise Molecular‐Level Modification of Nafion with Bismuth Oxide Clusters for High‐performance Proton‐Exchange Membranes

“…Polyoxometalates (POMs) are an important type of multivalent ionic molecular inorganic metal‐oxide nanoclusters, which are often used as functional inorganic fillers in PEMs to enhance the performance of the membrane due to their high‐water uptake ability, dispersity, thermal/chemical stability [12] . Among others, bismuth oxide clusters {H 6 Bi 12 O 16 } exhibited a variety of advantages as molecular‐level hybridization fillers.…”