Angewandte Chemie, Accepted Article.
To activate electronic and optical functions of the redox‐active metal‐organic framework, (Me 2 NH 2 )[In III (TTFTB)]·0.7C 2 H 5 OH· DMF (Me 2 NH 2 @ 1, TTFTB = tetrathiafulvalene‐tetrabenzoate, DMF = N,N ‐dimethylformamide), has been exchanged by tetrathiafulvalenium (TTF •+ ) and N,N ‘ ‐dimethyl‐ 4,4 ‘ ‐bipyridinium (MV 2+ ). These cations provide electron carriers and photosensitivity. The exchange retains the crystallinity allowing single‐crystal to single‐crystal post‐synthetic transformation to TTF@ 1 and MV@ 1 . X‐ray diffraction, 1 H‐NMR, FT‐IR, UV‐vis‐NIR and electron paramagnetic resonance (EPR) spectroscopies provide ample evidence of the successful cation‐exchange. Both TTF •+ and MV 2+ enhance the electrical conductivity by a factor of ~10 2 and the visible light induced photocurrent by 4 and 28 times respectively. EPR evidences synergetic effect involving charge transfer between the framework redox‐active TTFTB bridges and MV 2+ . The results demonstrate that functionalization of MOF by cation exchange without perturbing the crystallinity extends possibilities to achieve switchable materials.