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

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.