1：Experimental Design and Method Selection:

The study involved modifying g-C3N4 with celestite through calcination to create composites (CNSr-x), followed by characterization and photocatalytic activity evaluation under visible light irradiation for NO removal. Theoretical models include mechanisms of electron transfer and radical generation.

2：Sample Selection and Data Sources:

Samples included pure g-C3N4, celestite powder, and CNSr-x composites with varying celestite amounts (0.02, 0.05, 0.1, 0.2 g per 1 g g-C3N4). Data were sourced from laboratory experiments using synthetic gases and analytical instruments.

3：02, 05, 1, 2 g per 1 g g-C3N4). Data were sourced from laboratory experiments using synthetic gases and analytical instruments. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included a muffle furnace for calcination, XRD diffractometer (Bruker D8 Advance), TGA analyzer (STA 449F3, Netzsch), UV-vis spectrometer (Shimadzu UV-3700), fluorescence spectrometer (Hitachi F7000), SEM (ZEISS SUPRA55VP), XPS (VG Scientific ESCALAB Mark II), BET analyzer (Autosorb-IQ-MP), chemiluminescence NO analyzer (Thermo Scientific 42i), EPR instrument (Bruker E500), electrochemical workstation (CHI660C), and LED lamp (30 W). Materials included urea, celestite powder (purity ≥96%), SrSO4, nitric acid, DMPO, KI, K2Cr2O7, TBA, PBQ, Na?on, FTO glasses, KCl, and deionized water.

4：Experimental Procedures and Operational Workflow:

g-C3N4 was prepared by annealing urea at 550°C for 2 h. CNSr-x was prepared by mixing g-C3N4 with celestite and calcining at 400°C for 2 h. Characterization involved XRD, TGA, UV-vis, fluorescence, SEM, XPS, BET, EPR, and photoelectrochemical measurements. Photocatalytic activity was tested in a continuous-flow reactor with 50 mg catalyst, 600 ppb NO in air at 1 L/min flow rate, under 30 W LED visible light. NO, NO2, and NOT concentrations were monitored. Trapping experiments used scavengers for holes, electrons, ·OH, and ·O2-.

5：2-. Data Analysis Methods:

5. Data Analysis Methods: Data were analyzed using standard techniques: NO removal efficiency calculated as η = (1 - C/C0) × 100%, XRD for phase identification, TGA for thermal stability, UV-vis for band gap via Kubelka-Munk method, fluorescence for carrier recombination, SEM and XPS for morphology and composition, BET for surface area, EPR for radical detection, and electrochemical measurements for photocurrent and impedance.