Polarization-induced proton adsorption and charge separation in pyrene-based conjugated microporous polymers via substituent regulation for efficient photocatalytic hydrogen evolution

Abstract

Constructing photocatalysts with efficient light-harvesting abilities and charge separation propertiesis highly promising but still challenging for boosting photocatalytic hydrogen evolution from water. Herein, we report a simple and general polarization strategy through substituent regulation such as fluorination, chlorination and cyanation, to promote the photon capture and charge separation and unveil the latent structure–property–activity relationship in pyrene-based conjugated microporous polymers (CMPs). Notably, the introduction of fluorine, chlorine and cyano substituents onto the well-known full donor pyrene-benzene-based CMP network (Py-B) could induce a strong dipole along CF/Cl/CN bonds and the backbone local polarization enhancement due to their strong electron-withdrawing ability, which afforded CMPs have a variety of superior effects such as narrowing band gaps, expanding optical absorption, improving interfacial wettability and solid-state morphology, and promoting charge separation inside organic photocatalysts. As a result, 1.73/2.50/4.69-fold increases of the hydrogen evolution rates of the F/Cl/CN modified CMPs under visible light (λ > 420 nm) irradiation without Pt co-catalysts can be obtained in comparison with the counterpart Py-B (28.5/41.3/77.4 mmol g−1h−1 vs 16.5 mmol g−1h−1). Impressively, we find that the photocatalytic performance of this series of photocatalysts is linearly related to the dipole moment of polymers. Our studies reveal that the backbone local polarization enhancement induced by the substituent regulation could achieve high-performance organic photocatalysts toward solar-to-chemical energy conversion.