Molecular Orbital Engineering of Mixed-Addenda Polyoxometalates Boosts Light-Driven Hydrogen Evolution Activity
Manzhou Chi, Ying Zeng, Zhongling Lang, Huijie Li, Xing Xin, Yuanyuan Dong, Fangyu Fu, Guo‐Yu Yang, Hongjin Lv
Abstract
Inspired by the principle of molecular orbital engineering, two structurally well-defined polyoxometalate (POM)-based hydrogen-evolving catalysts, namely, [H 2 N(CH 3 ) 2 ] 9.24 Na 3 H 4 [Cu 2.06 W 1.94 O 2 (P 2 W 16 O 60 ) 2 ]·40H 2 O ( POM-1 ) and [H 2 N(CH 3 ) 2 ] 12.6 Na 2 H 3 [Cu 2.4 Mo 6.48 W 3.12 O 26 (P 2 W 12 O 48 ) 2 ]·27H 2 O ( POM-2 ), have been successfully synthesized and systematically characterized. Both POM compounds exhibited similar twin-Dawson-type polyoxoanion structures in which the monomer was connected through two μ 2 -O atoms bonded to the disordered Cu centers, as revealed by single-crystal X-ray diffraction analyses. Electronic structure analyses confirmed that the introduction of mix-addenda Mo atoms could readily adjust the lowest unoccupied molecular orbital (LUMO) energy level of POM-2, leading to a more negative lowest unoccupied molecular orbital (LUMO) position compared with that of POM-1 . Various spectroscopic and theoretical studies confirmed that the molecular orbital engineering modulation of POM-2 could provide a higher driving force for thermodynamically favorable and efficient electron transfer from the photosensitizer to POM-2 . In a three-component photocatalytic system, POM-2 exhibited the most efficient photocatalytic hydrogen evolution activity compared to all reported similar catalytic systems, achieving a catalytic turnover number (TON) of 5362 after 6 h of photocatalysis under visible-light irradiation.