Covalent lindqvist polyoxometalate-cubic polyhedral oligomeric silsesquioxane hybrid material: enhancing photocatalytic antibacterial activity and hydrogen production as a heterogeneous catalyst

Abstract

A novel approach for creating a hybrid material consisting of molecular polyoxometalate–polyhedral oligomeric silsesquioxane (POM–POSS) was developed, with a primary emphasis on overcoming the challenges related to the solar-driven production of hydrogen (H₂) and the elimination of harmful bacteria in polluted wastewater. Herein, the Lindqvist-type polyoxometalate cluster, tetrabutylammonium hexamolybdate [LPOM(Mo)] and the aminopropyl heptaisobutyl silsesquioxane (POSS–NH₂) were combined through covalent linkage to form the POM organoimido POSS hybrid material by a dehydration reaction. Various analytical techniques, such as FT-IR spectroscopy, BET, NMR spectroscopy, and ESI–MS, were used to investigate the development of a covalent POM–POSS hybrid material. HR-TEM images of the POM–POSS hybrid material demonstrated that the flat sheets were rectangular in shape with a size distribution ranging from 2.5 ± 0.2 μm in length to 0.2 ± 0.02 μm in width. The POM–POSS hybrid material showed a more efficient photocatalytic system compared to POM prompted by a visible region absorption shift, photoluminescence quenching effect, and increased photocurrent generation (2.1 μA cm⁻²). Antibacterial tests demonstrated the highest photoinactivation against Escherichia coli (E. coli) cells after 45 min of sunlight exposure. The POM–POSS hybrid material exhibited excellent H₂ generation (2461 μmol g⁻¹ h⁻¹) than LPOM(Mo) (2051 μmol g⁻¹ h⁻¹) owing to the improved photocatalytic system via the covalently linked organoimide ligand from POSS–NH₂. Furthermore, the reusability of the POM–POSS hybrid material was assessed by measuring its photocatalytic H₂ production rate over ten consecutive cycles, and the stability of the catalytic activity was demonstrated. These findings demonstrate a rational method for constructing POM–POSS material with controlled chemical composition and architecture for H₂ production under abundant sunlight.