1：Experimental Design and Method Selection:

A facile and controllable in situ reduction strategy using glyoxal as the reductant to create surface oxygen vacancies (OVs) on Aurivillius-phase Sr2Bi2Nb2TiO12 nanosheets. The nanosheets were prepared by a mineralizer-assisted soft-chemical method (hydrothermal process with sodium hydrate as mineralizer). Theoretical models and algorithms include density functional theory (DFT) calculations, ultrafast transient absorption spectroscopy, and in situ Fourier transform infrared analysis.

2：Sample Selection and Data Sources:

Samples include Sr2Bi2Nb2TiO12 nanosheets (SBNT-HR) and OVs-abundant versions (SBNT-HR-X with X=0.3, 0.5, 1 ml glyoxal), and bulk counterpart (SBNT-SSR) prepared by high-temperature solid-state reaction. Data sources are experimental measurements from these samples.

3：3, 5, 1 ml glyoxal), and bulk counterpart (SBNT-SSR) prepared by high-temperature solid-state reaction. Data sources are experimental measurements from these samples. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment includes transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution TEM (HRTEM), UV-vis diffuse reflectance spectroscopy (DRS), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), in situ Fourier transform infrared (FTIR) spectroscopy, ultrafast transient absorption (TA) spectroscopy, photocurrent response measurements, electrochemical impedance spectroscopy (EIS), and CO2 adsorption isotherms. Materials include Sr2Bi2Nb2TiO12, glyoxal, sodium hydrate, and gases like CO2 and Ar.

4：Experimental Procedures and Operational Workflow:

Synthesis of nanosheets via hydrothermal method, introduction of OVs with glyoxal treatment, characterization using TEM, SAED, HRTEM, DRS, EPR, XPS, FTIR, TA spectroscopy, EIS, and photocurrent measurements. Photocatalytic CO2 reduction tests in a gas-solid reaction system under simulated solar light, with product analysis using mass spectrometry (MS) for 13CO2 labeling.

5：Data Analysis Methods:

Analysis of spectra and data from various techniques, biexponential fitting for TA decay kinetics, calculation of band gaps, adsorption energies via DFT, and statistical comparison of photocatalytic rates.