1：Experimental Design and Method Selection:

The study involved synthesizing TiO2@Si(HIPE) monoliths using a sol–gel process with high internal phase emulsions (HIPE) as templates to create hierarchical porosity. Photonic investigations and photocatalytic tests were conducted to evaluate light diffusion and CO2 reduction performance. A Langmuir–Hinshelwood kinetic model was applied to analyze reaction rates.

2：Sample Selection and Data Sources:

Samples included TiO2@Si(HIPE) monoliths with varying synthesis conditions (e.g., fresh vs. aged precursor) and commercial TiO2 powder (P25 from Degussa) as a reference. Data were obtained from material characterizations (SEM, TEM, XRD, etc.), photonic measurements, and photocatalytic experiments.

3：List of Experimental Equipment and Materials:

Equipment included SEM (FEI Nova nano SEM 450), TEM (JEOL JEM 2200FS), XRD (PANalytical X’Pert PRO MPD), UV–vis spectrometer (Agilent CARY 60), mercury porosimeter (Micromeritics Autopore IV), and BET surface area analyzer (Micromeritics ASAP 2420). Materials included titanium(IV) isopropoxide, tetraethyl orthosilicate, tetradecyltrimethylammonium bromide, isopropanol, hydrochloric acid, dodecane, and CO2 gas.

4：0). Materials included titanium(IV) isopropoxide, tetraethyl orthosilicate, tetradecyltrimethylammonium bromide, isopropanol, hydrochloric acid, dodecane, and CO2 gas. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Synthesis involved creating Si(HIPE) foams via emulsion templating, followed by impregnation with TiO2 precursor and thermal treatment. Characterizations included structural and optical analyses. Photocatalytic tests involved CO2 reduction under UV irradiation, with product analysis.

5：Data Analysis Methods:

Data were analyzed using diffusion equation fits for photonic data, Scherrer equation for crystallite sizes, and kinetic modeling based on Langmuir–Hinshelwood formalism with Beer–Lambert law for light attenuation.