Among HAT-mediated C-C coupling reactions, acceptorless (oxidant-free) dehydrogenative reactions are notably rare (ref 56). Efforts were therefore undertaken to identify the potential hydrogen acceptor. The reaction vessel was rigorously deoxygenated by preparing all reagents and solvent in a glovebox with ideal condition. After irradiation, the air above the reaction solution expanded and the vessel was under positive pressure even after cooled to room temperature for 2 more hours (fig. ). Surprisingly, gas chromatography (GC) analysis of the headspace revealed no detectable hydrogen signal. The only discernible byproduct in the reaction mixture was hydrogenated benzylidene malononitrile, which accounted for less than 10% of the limiting reagent (fig. ), and the excess aniline was recovered with little loss. Based on the evidence above, we proposed the novel catalytic activity of CD-2 was majorly resulted by its more oxidative redox window compared to CD-1, potentially enabling the oxidation of radical intermediates (fig. ). Further investigations into the reaction mechanism and the identity of the evolved gas species are ongoing and will be reported in future.