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Modulating Photoinduced Charge Separation in Metal–Azolate Frameworks

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journal contribution
posted on 07.01.2021, 00:30 by Ting-Ting Liu, Tian-Fu Liu, Xin-Ping Wu, Xue-Qing Gong
Effective separation of photogenerated charge carriers can bring about long-lived photoexcited states. Here, we calculate the electronic and optical properties of four pyrazolate-based metal–azolate frameworks (MAFs) (with different inorganic nodes and/or organic linkers) and their isostructural 1,2,3-triazolate and tetrazolate derivatives. We find that a MAF having nitrogen-richer azolates gives more efficient ligand-to-metal transfer of photoexcited electrons and hence more effective charge separation, in comparison with a MAF having nitrogen-leaner azolates; this trend was consistently observed in all series of isostructural MAFs. We therefore propose that increasing the number of electron-withdrawing N atoms in azolates (e.g., pyrazolate) can enhance the charge separation in MAFs. This strategy for modulating photoinduced charge separation in MAFs can be generally applicable and expected to be superior to the widely used strategy based on metal exchange in many cases.

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