Syntheses and catalytic properties of two new multi-manganese-substituted silicotungstates

Abstract

Transition-metal-substituted polyoxometalates have attracted attention due to their remarkable physicochemical properties and applications in many research areas. Two new multi-manganese-substituted silicotungstates, tetramer [{Mn₃Cl(OH)₃(SiO₄)}₄(SiW₉O₃₄)₄]^36- (1) and banana-shaped [((MnOH₂)_0.5Mn₂SiW₉O₃₄)₂(SiW₆O₂₆)]^22- (2), were prepared under hydrothermal conditions and characterized by single-crystal X-ray diffraction, FT-IR spectroscopy, etc. Compound 1 comprises four {SiW₉O₃₄} fragments, one {Mn₃Cl(OH)₃}₄ cluster and four {SiO₄} groups; it can form a 1 D-chain by connecting [{Mn₃Cl(OH)₃(SiO₄)}₄(SiW₉O₃₄)₄]³⁶⁻ cluster units with Na⁺ cations. Banana-shaped 2 consists of two {(Mn^IIOH₂)_0.5Mn^III₂SiW₉O₃₄} fragments connected by a hexavacant {SiW₆O₂₆} motif, and it displays an interesting 3-D architecture by bridging banana-shaped [((Mn^IIOH₂)_0.5Mn^III₂SiW₉O₃₄)₂(SiW₆O₂₆)]^18- polyanion with four-member Na-cluster. 3-D packing of 2 along the c-axis creates two types of elliptical channels with sizes of 7.86 Å × 13.35 Å and 16.03 Å × 25.28 Å, respectively. Also, while coupling with [Ir(ppy)₂(dtbbpy)]⁺ as photosensitizer and triethanolamine (TEOA) as sacrificial electron donor, both compounds show decent catalytic activity towards hydrogen production under visible LED light irradiation.

Graphical Abstract

Keywords:

• Polyoxometalates
• multinuclear manganese
• manganese-substituted silicotungstates
• visible-light-driven hydrogen production

Additional information

Funding

This work is financially supported by the National Natural Science Foundation of China (21871025 and 21831001), the Recruitment Program of Global Experts (Young Talents) and BIT Excellent Young Scholars Research Fund.