Construction of a metal-free photocatalyst via encapsulation of 1,2,3,5-tetrakis(carbazole-9-yl)-4,6-dicyanobenzene in a carboxymethylcellulose-based hydrogel for photocatalytic lactic acid production

Abstract

The efficient application of solar energy to realize photocatalytic biomass conversion to value-added chemicals is of significance. Herein, we propose a novel metal-free photocatalyst (4CzIPN@CMC-HG), which was prepared by encapsulating 1,2,3,5-tetrakis(carbazole-9-yl)-4,6-dicyanobenzene (4CzIPN) in a carboxymethylcellulose-based hydrogel (CMC-HG) using a one-step thermal polymerization strategy. 4CzIPN@CMC-HG has an efficient photon-to-electron conversion rate, excellent visible light absorption, fast photogenerated carrier migration/separation, and high photocatalytic activity, with 90.7% yield of lactic acid (LA) and 100.0% conversion of xylose due to the synergistic effects between 4CzIPN and CMC-HG. 4CzIPN@CMC-HG showed remarkable universality and excellent stability, and the 1000-times amplification system indicated that this system has a potential industrial application in LA production. Furthermore, trapping experiments indicated that ˙OH, h⁺, ¹O₂, and ˙O₂⁻ contributed to LA synthesis, with ˙O₂⁻ taking a leading role. These results showed the promising application prospects of metal-free photocatalysts in the photocatalytic biomass conversion to value-added chemicals.