Construction of heterostructures has been an effective approach for suppressing recombination of photogenerated charge carriers of graphitic carbon nitride (g-C3N4) materials and facilitating solar energy harvesting. In this paper, superior thin B-doped g-C3N4 nanosheets are synthesized via mechano-chemical pre-treatment and two-step thermal polymerization (at 600 and 700 °C) using boric acid and melamine as the precursors. The in-situ growth of W18O49 nanobelts on B-g-C3N4 nanosheets is attained via solvothermal synthesis. W18O49 nanobelts are horizontally implanted onto g-C3N4 nanosheets to construct a Z-scheme heterostructure with extended light absorption in near infrared range. Well-developed interfaces between W18O49 and B-g-C3N4 is crucial for the enhanced transfer efficiency of photogenerated charge carriers. The W18O49/B-g-C3N4 samples fabricated using optimized conditions show excellent photocatalytic performance in NO and 4-nitrophenol oxidation conversion. The W18O49/B-g-C3N4 composites attain a NO removal efficiency of 64 % (at an initial NO concentration of 600 ppb in air) with a low NO2 selectivity (6.4 %), which is more efficient than that of the commercial P25 (TiO2, with a 40 % NO removal rate). These are mainly attributed to the formed Z-scheme W18O49/B-g-C3N4 layered heterostructure, increased specific surface area and improved interfacial structure. The heterostructure construction, light absorption range extension, and adjustment on band gap of the composite material are discussed in detail. In full-spectrum irradiation condition, the W18O49/B-g-C3N4 heterostructures also show excellent light-assisted 4-nitrophenol elimination (via selective hydrogenation to valuable 4-aminophenol) performance, attaining a 99 % of 4-nitrophenol reduction rate.

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