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arXiv · 2512.17778

Mechanistic Origin of Charge Separation and Enhanced Photocatalytic Activity in D-$\pi$-A-Functionalized UiO-66-NH$_2$ MOFs

Anastasiia Kultaeva·Volodymyr Vasylkovskyi·Andreas Sperlich·Eugenio Otal·Katsuya Teshima·Wolf Gero Schmidt·Timur Biktagirov
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Abstract

Donor-$\pi$-acceptor (D-$\pi$-A) functionalization of MOF linkers can enhance visible-light photocatalytic activity, yet the mechanisms responsible for these effects remain unclear. Here we combine EPR spectroscopy, transient photoluminescence, and first-principles calculations to examine how diazo-coupled anisole, diphenylamine (DPA), and N,N-dimethylaniline (NNDMA) groups modify the photophysics of UiO-66-NH$_2$. All donor units introduce new occupied states near the valence-band edge, enabling charge separation through dye-to-framework electron transfer. Among them, the anisole-modified material stands out for facilitating efficient intersystem crossing into a triplet charge-transfer configuration that suppresses fast recombination and yields long-lived charge carriers detectable by photo-EPR. Meanwhile, bulkier donors such as DPA and NNDMA - despite their stronger electron-donating character - also tend to introduce defect-associated trap states. These results underscore the interplay between donor-induced electronic-structure changes, triplet pathways, and defect-mediated recombination, offering a mechanistic basis for tuning photocatalytic response in D-$\pi$-A-modified MOFs.

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BibTeXRIS

Anastasiia Kultaeva, Volodymyr Vasylkovskyi, Andreas Sperlich, Eugenio Otal, Katsuya Teshima, Wolf Gero Schmidt, Timur Biktagirov. 2025-12-19. Mechanistic Origin of Charge Separation and Enhanced Photocatalytic Activity in D-$\pi$-A-Functionalized UiO-66-NH$_2$ MOFs. https://doi.org/10.1039/d5mh02418h

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