Decorating Ag₃PO₄ nanodots on mesoporous silica-functionalized NaYF₄:Yb,Tm@NaLuF₄ for efficient sunlight-driven photocatalysis: synergy of broad spectrum absorption and pollutant adsorption-enrichment

Efficiently harvesting solar energy for photocatalysis remains a challenge because near infrared (NIR) light with low excitation energy cannot be directly utilized by general semiconductor photocatalysts, although it makes up 46% of the solar spectrum. Herein, a broad-spectrum photocatalyst with pollutant adsorption-enrichment capability to enable natural sunlight-driven photocatalysis was synthesized by decorating a small amount of silver orthophosphate (Ag₃PO₄) nanodots on mesoporous silica (mSiO₂)-functionalized upconversion nanoparticles (UCNPs; NaYF₄:Yb,Tm@NaLuF₄). The UCNPs play the role of broadening the absorption spectrum by upconverting NIR light into visible light, which can be absorbed by the Ag₃PO₄ nanodots. The functionalized hydrophilic mSiO₂ shell not only facilitates the decoration of Ag₃PO₄ nanodots but is also capable of adsorbing and enriching pollutants around the Ag₃PO₄ nanodots to enhance the photocatalytic activity. Upon natural sunlight irradiation, the as-prepared photocatalyst (UCNP@mSiO₂-Ag₃PO₄) exhibited remarkable photocatalytic activity with degradation rate constants of 0.24 and 0.051 min⁻¹ under stirring and static conditions, exceeding that of the pure Ag₃PO₄ sample by factors of 4.2 and 12.5, respectively. Thus, it can be anticipated that the design of photocatalysts with the synergy of broadband absorption and pollutant adsorption-enrichment will be a promising strategy to realize efficient sunlight-driven photocatalysis, even without extra mechanical stirring for future scaled-up water treatment.