Phosphate‐Templated Encapsulation of a {CoII4O4} Cubane in Germanotungstates as Carbon‐Free Homogeneous Water Oxidation Photocatalysts

• DOI: 10.1002/cssc.202100506
• Publication Date: 2021-04-09T14:54:38Z
• Authors: Emir Al‐Sayed; Sreejith P. Nandan; Elias Tanuhadi; Gerald Giester; Marco Arrigoni; Georg K. H. Madsen; Alexey Cherevan; Dominik Eder; Annette Rompel
• Keywords: Cubane; Encapsulation; Carbon fibers

The ever-growing interest in sustainable energy sources leads to a search for an efficient, stable, and inexpensive homogeneous water oxidation catalyst (WOC). Herein, the PO43- templated synthesis of three abundant-metal-based germanotungstate (GT) clusters Na15 [Ge4 PCo4 (H2 O)2 W24 O94 ] ⋅ 38H2 O (Co4 ), Na2.5 K17.5 [Ge3 PCo9 (OH)5 O)4 W30 O115 45H2 (Co9 Na6 K16 P4 Co20 (OH)14 O)18 W36 O150 61H2 (Co20 ) with non-, quasi-, or full cubane motifs structurally strongly reminiscent naturally occurring {Mn4 Ca} oxygen evolving complex (OEC) photosystem II was achieved. Under conditions tested, all GT-scaffolds were active molecular WOCs, Co9 outperforming well-known Na10 [Co4 (PW9 O34 )2 {Co4 P2 W18 } by factor 2 as shown direct comparison their turnover numbers (TONs). With TONs up 159.9 frequency 0.608 s-1 currently represents fastest Co-GT-based WOC, photoluminescence emission spectroscopy provided insights into its photocatalytic WOC mechanism. Cyclic voltammetry, dynamic light scattering, UV/Vis IR showed recyclability integrity catalysts under applied conditions. experimental results supported computational studies, which highlighted that facilitated due higher highest occupied orbital electrons compared Co4 .