Light Ignites Lattice Oxygen in an Asymmetric Motif

Lattice-oxygen-mediated pathways bypass the energy-intensive steps that constrain adsorbate-mediated catalysis. Activating these pathways under mild conditions, however, means breaking metal-oxygen bonds that are, by design, strong. Asymmetric M1-O-M2 motifs, in which a bridging oxygen sits between two cations of different electronic character, decouple oxygen activation from oxygen release by distributing these functions across chemically distinct sites. Here, we show that a Cu-doped In2O3 system with a well-defined asymmetric Cu-O-In unit exhibits enhanced photoinduced lattice oxygen activity. Series (quasi) in situ spectroscopy captures the activation, consumption, and replenishment of lattice oxygen under illumination in real time. Photogenerated carriers populate around the Cu-O site preferentially, weakening the Cu-O bond enough to extract lattice oxygen at room temperature. The optimized material, Cui-In2O3, gives a response of 32.4 toward 5 ppm of H2S under visible light. The results connect local coordination asymmetry directly to photoinduced oxygen functionality and suggest a route toward photodriven catalysts built around asymmetric oxygen sites.