Interfacial Ti−S Bond Modulated S‐Scheme MOF/Covalent Triazine Framework Nanosheet Heterojunctions for Photocatalytic C−H Functionalization

An S-Scheme heterojunction built up from titanium-organic framework (MOF-902) @thiophene-based covalent triazine framework (CTF-Th) nanosheets was prepared. It has controllable interfacial oxygen vacancies (OVs). This heterojunction demonstrates high efficiency in photocatalytic C3-acylation of indoles with a yield 8.2 times larger than pristine CTF-Th or MOF-902. The reaction could be applied to a range of substrates.

Abstract

Constructing photocatalyst systems to functionalize the inert C−H bonds has attracted extensive research interest. However, purposeful modulation of interfacial charge transfer in heterostructures remains a challenge, as it usually suffers from sluggish kinetics. Reported herein is an easy strategy to construct the heteroatom-induced interface for developing the titanium-organic frameworks (MOF-902) @ thiophene-based covalent triazine frameworks (CTF-Th) nanosheets S-scheme heterojunctions with controllable oxygen vacancies (OVs). Specifically, Ti atoms were first anchored onto the heteroatom site of CTF-Th nanosheets, and then grown into MOF-902 via an interfacial Ti−S linkage, generating OVs. Using in situ X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS) spectroscopy and density functional theory (DFT) calculations, the enhanced interfacial charge separation and transfer induced by moderate OVs in the pre-designed S-scheme nanosheets was validated. The heterostructures exhibited an improved efficiency in photocatalytic C3-acylation of indoles under mild conditions with a yield 8.2 times larger than pristine CTF-Th or MOF-902 and enabled an extended scope of substrates (15 examples). This performance is superior to state-of-the-art photocatalyst and can be retained, without significant loss, after 12 consecutive cycles.

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