1：Experimental Design and Method Selection:

A modified sol-gel method facilitated by a nanocasting procedure was used to synthesize mesoporous composites of Bi0.5Y0.5VO4 and SiO2 (BYV-SiO2) with SBA-15 as the silica matrix, followed by calcination at various temperatures. The design aimed to create isolated solid-solution photocatalysts with controlled size and crystallinity.

2：5Y5VO4 and SiO2 (BYV-SiO2) with SBA-15 as the silica matrix, followed by calcination at various temperatures. The design aimed to create isolated solid-solution photocatalysts with controlled size and crystallinity. Sample Selection and Data Sources:

2. Sample Selection and Data Sources: Samples were categorized into groups based on calcination temperature (mBYV-T), mass filling ratio (mBYV-M), citric acid to cation salts molar ratio (mBYV-Cx), and type of silica support (mBYV-xSiO2). Characterization data were obtained from XRD, UV-Vis DRS, BET surface area measurements, TEM, SEM, XPS, contact angle measurements, NMR, electrochemical analyses, and XAS.

3：2). Characterization data were obtained from XRD, UV-Vis DRS, BET surface area measurements, TEM, SEM, XPS, contact angle measurements, NMR, electrochemical analyses, and XAS. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included a D8 Advance diffractometer (Bruker) for XRD, UV-Vis spectrophotometer (Shimadzu) for DRS, TriStar II 3020 Micromeritics porosimeter for BET/BJH, Tecnai G2 Spirit BioTWIN TEM, Sirion 200 SEM, FEI Talos F200X for HRTEM/HAADF-STEM, Kratos Axis Ultra DLD spectrometer for XPS, DSA-100 contact angle instrument (Kruess), Acorn Area NMR (XiGo Nanotools), CHI 660D electrochemical station, and Shanghai Synchrotron Radiation Facility for XAS. Materials included SBA-15 silica, metal nitrates, citric acid, ethylene glycol, chloroplatinic acid for Pt loading, and deionized water.

4：Experimental Procedures and Operational Workflow:

Synthesis involved impregnating SBA-15 with precursor solutions, calcination at specified temperatures, Pt photodeposition, and photocatalytic testing in a Pyrex reaction cell with a 300 W Xe lamp. Gas evolution was measured hourly using gas chromatography.

5：Data Analysis Methods:

XRD patterns were analyzed for phase identification, UV-Vis DRS used Kubelka-Munk method, BET/BJH for surface area and pore size, TEM/SEM for morphology, XPS for surface composition, electrochemical data for photocurrent and Mott-Schottky analysis, and XAS for Pt coordination. FDTD simulations in MATLAB were used for optical absorption modeling.