Author(s) Qin, J.; Yuan, S.; Zhang, L.; Li, B.; Du, D.Y.; Huang, N.; Guan, W.; Drake, H.; Pang, J.; Lan, Y.Q.; Alsalme, A.; Zhou, H.C.
Journal J Am Chem Soc
Date Published 2019 Jan 09

The incorporation of large π-conjugated ligands into metal-organic frameworks (MOFs) can introduce intriguing photophysical and electrochemical properties into the framework. However, these effects are often hindered by the strong π-π interaction and the low solubility of the arylated ligands. Herein, we report the synthesis of a porous zirconium-based MOF, Zr6(μ3-O)4(μ3-OH)4(OH)6(H2O)6(HCHC) (PCN-136, HCHC = hexakis(4-carboxyphenyl)hexabenzocoronene), which is composed of a hexacarboxylate linker with a π-conjugated hexabenzocoronene moiety. Direct assembly of the Zr4+ metal centers and the HCHC ligands was unsuccessful due to the low solubility and the unfavorable conformation of the arylated HCHC ligand. Therefore, PCN-136 was obtained from aromatization-driven post-synthetic annulation of the hexaphenylbenzene fragment in a preformed framework (pbz-MOF-1) to avoid π-π stacking. This post-synthetic modification was done through a single-crystal-to-single-crystal transformation and was clearly observable utilizing single crystal X-ray crystallography. The formation of large π-conjugated systems on the organic linker dramatically enhanced the photo responsive properties of PCN-136. With isolated hexabenzocoronene moieties as photosensitizers and Zr-oxo clusters as catalytic sites, PCN-136 was employed as an inherent photocatalytic system for CO2 reduction under visible-light irradiation, which showed increased activity compared with pbz-MOF-1.

DOI 10.1021/jacs.8b11042
ISSN 1520-5126
Citation J Am Chem Soc. 2019.

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