Coupling Red-to-blue Upconversion Organic Microcrystals with Cd 0.5 Zn 0.5 S for Efficient and Durable Photocatalytic Hydrogen Production.

For semiconductor photocatalysts with excellent performance in solar H 2 production, broadening the utilization of solar irradiation is highly necessary to further improve the solar conversion efficiency. Herein, we combined a Cd 0.5 Zn 0.5 S photocatalyst with DPA/PdTPTBP microcrystals capable of red-to-blue photon upconversion, realizing substantial performance enhancement and an apparent quantum yield of 0.16% for H 2 production driven by sub-bandgap photons (600∼650 nm). Meanwhile, this system could smoothly work with H 2 production rate of 1.40 mmol g -1  h -1 for as long as 40 hours under 200 mW/cm 2 irradiation with only 3% attenuation of photocatalytic activity. Moreover, the O 2 -barrier property of DPA/PdTPTBP microcrystals assures that photocatalytic H 2 production remains effective in the presence of 10% O 2 by volume, which offers an opportunity for the photocatalytic application in O 2 -enriched environments. The combination of O 2 -resistant upconversion microcrystals and semiconductor catalysts is the most successful solution for the construction of TTA-UC-based photocatalytic H 2 production system so far. The present study provides a clear guideline for designing new TTA-UC-based photocatalytic systems.