Coordination Synergy between Iridium Photosensitizers and Metal Nanoclusters Leading to Enhanced CO₂ Cycloaddition...

The achievement of photocatalytic CO₂ and epoxide cycloaddition under mild conditions such as room temperature and atmospheric pressure is important for green chemistry, which can be achieved by developing coordination synergies between catalysts and photosensitizers. In this context, we exploit the use of coordinate bonds to connect pyridine-appended iridium photosensitizers and catalysts for CO₂ cycloaddition, which is systematically demonstrated by ¹H nuclear magnetic resonance titration and X-ray photoelectron spectroscopic measurements. It is shown that the hybrid Ir(Cltpy)₂/Mn₂Cd₄ photocatalytic system with coordination synergy exhibits excellent catalytic performance (yield ≈ 98.2%), which is 3.75 times higher than that of the comparative Ir(Cltpy-Ph)₂/Mn₂Cd₄ system without coordination synergy (yield ≈ 26.2%), under mild conditions. The coordination between the Mn₂Cd₄ catalyst and the Ir(Cltpy)₂ photosensitizer enhances the light absorption and photoresponse properties of the Mn₂Cd₄ catalyst. This has been confirmed through transient photocurrent, electrochemical impedance, and electron paramagnetic tests. Consequently, the efficiency of cycloaddition was enhanced by utilizing mild conditions.