1：Experimental Design and Method Selection:

The study used a non-hydrolytic sol–gel (NHSG) spin-coating method to prepare WO3 porous films on glass substrates. Ethanol served as the oxygen-donor, and PEG was used as a structure-directing agent. The synthesis parameters varied were aging time (2-5 hours), PEG content (0-0.6 g), and calcination temperature (300-600°C).

2：6 g), and calcination temperature (300-600°C). Sample Selection and Data Sources:

2. Sample Selection and Data Sources: Glass substrates with a diameter of 2.5 cm were used. Materials included tungsten hexachloride (WCl6), absolute ethanol, dimethylformamide (DMF), and polyethylene glycol (PEG). All reagents were analytic grade.

3：5 cm were used. Materials included tungsten hexachloride (WCl6), absolute ethanol, dimethylformamide (DMF), and polyethylene glycol (PEG). All reagents were analytic grade. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included a vacuum spin coater (VTC-100, Kejing Auto-instrument Co., Ltd), X-ray diffractometer (PANalytical X’Pert Pro), field emission scanning electron microscope (ZEISS Ultra Plus), transmission electron microscope (JEM2100), and gas sensing test system (WS-30A, Winsen Electronics Technology Co., Ltd). Materials included WCl6, ethanol, DMF, PEG, and glass substrates.

4：Experimental Procedures and Operational Workflow:

The precursor solution was prepared by dissolving WCl6 and PEG in a mixture of ethanol and DMF, aged at 70°C. Spin-coating was performed at 1000 rpm for 20 seconds. Films were dried at 70°C and calcined at specified temperatures. Characterization involved XRD, SEM, TEM, and gas sensing measurements.

5：Data Analysis Methods:

XRD patterns were analyzed for crystallinity and structure. SEM and TEM images were used to observe morphology. Gas sensing responses were measured as Rgas/Rair, with response and recovery times defined as times to reach 90% of equilibrium value.