Synthesis of 1,4-diethynylbenzene-based conjugated polymer photocatalysts and their enhanced visible/near-infrared-light-driven hydrogen production activity

Some conjugated polymer organic semiconductors with linear or network structures and tunable band gaps are found to be efficient metal-free photocatalysts for H-2 production. In the present work, three 1,4-diethynylbenzene-based linear conjugated polymer organic semiconductors (named P7-E, B-BT 1,4-E, and P17-E) were synthesized by palladium-catalyzed Sonogashira-Hagihara cross-coupling poly condensation. Compared with three reported 1,4-benzene-based linear conjugated polymer organic semiconductors (P7, B-BT-1,4, and P17), the ethynyl group is introduced into their backbones and the absorption edge is extended by 150-190 nm to the red/NIR light region (up to similar to 750 nm). Importantly, a negative shift of LUMO levels and enhanced photocurrent intensity are also observed, and their visible-light-induced H-2 production activity is improved dramatically. P7-E exhibits the highest H2 production rate of 180.7 mu mol/h under,lambda> 420 nm irradiation even without Pt co-catalyst loaded. Moreover, the apparent quantum yield (AQY) value of P7-E is 4.2% at 420 nm, which is much higher than that reported so far for P7. The present result indicates that small changes in the chemical structure of conjugated polymers can significantly tune their optical and photocatalytic properties, which provides a new direction for attaining more efficient organic conjugated polymer photocatalysts. (C) 2017 Elsevier Inc. All rights reserved.