Facile Energy Gap Tuning in Nanographene-MOFs

The utilization of metal-organic frameworks (MOFs) in photocatalysis applications requires light-responsive architectures with tunable optical bandgaps. Here, we demonstrate a facile approach to optical bandgap tuning via post-synthetic modifica-tions of pbz-MOF-1, a Zr-based MOF with polyphenylene ligands. A simple reaction of pbz-MOF-1 with FeCl3 was shown to induce three different chemical reactions of the ligands: oxidative dehydrogenation, chlorination and one/two electron oxi-dation of the ligands. The result of these reactions was a gradual decrease in the optical bandgap from 2.95 eV to as little as 0.69 eV. Time-resolved optical spectroscopy and electron paramagnetic resonance spectroscopy, coupled with density functional theory calculations provide insights into the mechanisms of bandgap tuning using chemical oxidation methods. The facile bandgap tuning report here has promising application in the utilization of photo-responsive MOFs in photocatalysis, sensing and other light-triggered applications.