In situ time-resolved spectroscopy is an effective method to monitor the catalysis reaction in real time and reveal the catalytic mechanistic pathway.The dynamic evolution of coordination and electronic structures of catalytic active sites during the CO2 reduction reaction is still a “black box,” impeding the design of high-efficiency catalysts.In a recent report published in J.Am.Chem.Soc., by multiple in situ time-resolved spectroscopy, Xiong and co-workers successfully detected the dynamic evolution and photoinduced charge transfer process of terpyridine nickel(Ⅱ) complex catalysts in photocatalytic CO2 reduction reactions.