Abstract
For the first time, covalently anchoring size selected silver nanoclusters [Ag(44)(MNBA)(30)] on the Bi(2)S(3)@UiO-66-NH(2) and MoS(2)@UiO-66-NH(2) heterojunctions were constructed as novel photocatalysts for photodegradation of methylene blue (MB) dye. The anchoring of Ag(44) on MoS(2)@UiO-66-NH(2) and Bi(2)S(3)@UiO-66-NH(2) heterojunctions extended the light absorption of UiO-66-NH(2) to the visible region and improved the transfer and separation of photogenerated charge carriers through the heterojunctions with a unique band gap structure. The UV-Vis-NIR diffuse reflectance spectroscopic analysis confirmed that the optical absorption properties of the UiO-66-NH(2) were shifted from the UV region at 379 nm to the visible region at ~ 705 nm after its doping with Bi(2)S(3) nanorods and Ag(44) nanoclusters (Bi(2)S(3)@UiO-66-NH-S-Ag(44)). The prepared Bi(2)S(3)@UiO-66-NH-S-Ag(44) and MoS(2)@UiO-66-NH-S-Ag(44) photocatalysts exhibited exceptional photocatalytic activity for visible light degradation of MB dye. The photocatalysts exhibited complete decolorization of the MB solution (50 ppm) within 90 and 120 min stirring under visible light irradiation, respectively. The supper photocatalytic performance and recycling efficiency of the prepared photocatalysts attributed to the covalent anchoring of the ultra-small silver clusters (Ag(44)) on the heterojunctions surface. The X-ray photoelectron spectroscopic analysis confirmed the charge of the silver clusters is zero. The disappearance of the N-H bending vibration peak of primary amines in the FTIR analysis of Bi(2)S(3)@UiO-66-NH-S-Ag(44) confirmed the covalent anchoring of the protected silver nanoclusters on the UiO-66-NH(2) surface via the condensation reaction. The Bi(2)S(3)@UiO-66-NH-S-Ag(44) catalyst exhibited excellent recyclability efficiency more than five cycles without significant loss in activity, indicating their good potential for industrial applications. The texture properties, crystallinity, phase composition, particle size, and structural morphology of the prepared photocatalysts were investigated using adsorption-desorption N(2) isotherms, X-ray diffraction (XRD), HR-TEM, and FE-SEM, respectively.