Host–Guest Interactions in Metal–Organic Frameworks Doped with Acceptor Molecules as Revealed by Resonance Raman Spectroscopy

[Image: see text] Metal–organic frameworks (MOFs) represent a class of porous materials whose properties can be altered by doping with redox-active molecules. Despite advanced properties such as enhanced electrical conduction that doped MOFs exhibit, understanding physical mechanisms remains challenging because of their heterogeneous nature hindering experimental observations of host–guest interactions. Here, we show a study of charge transfer between Mn-MOF-74 and electron acceptors, 7,7,8,8-tetracyanoquinodimethane (TCNQ) and XeF(2), employing selective enhancement of Raman scattering of different moieties under various optical-resonance conditions. We identify Raman modes of molecular components and elucidate that TCNQ gets oxidized into dicyano-p-toluoyl cyanide (DCTC(–)) while XeF(2) fluorinates the MOF upon infiltration. The framework’s linker in both cases acts as an electron donor as deduced from blue shifts of the C–O stretching mode accompanied by the emergence of a quinone-like mode. This work demonstrates a generally applicable methodology for investigating charge transfer in various donor–acceptor systems by means of resonance Raman spectroscopy.