Abstract <p>This article used one simple heat treatment to prepare high efficient Sn₂₁Cl₁₆(OH)₁₄O₆/SnO₂ composite photocatalysts using anhydrous SnCl₂ and NaOH powders as raw materials. The structural characteristics of the synthesized catalysts were studied using analysis techniques such as powder XRD, SEM and DRS. The research results showed that Sn₂₁Cl₁₆(OH)₁₄O₆/SnO₂ composites were prepared by heat treatment. An increase in the content of NaOH in the raw material can promote the transformation of Sn₂₁C-l₁₆(OH)₁₄O₆ into SnO₂. As the content of NaOH increased, the corresponding content of SnO₂ in the product also increased. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images reveal that the sample was composed of aggregates formed by the focusing of a large number of nanocrystals. DRS analysis shows that compared to SnO₂ reagent and single-phase Sn₂₁Cl₁₆(OH)₁₄O₆, the synthesized sample had much stronger absorption ability in the visible light region, and the bandgap value of the samples were obviously reduced. The photocatalytic experiment proves that the prepared catalysts exhibits excellent photocatalytic degradation ability. Under simulated sunlight and visible light irradiation, samples with lower NaOH content in the raw material can completely degrade methyl orange in 6 minutes and 15 min, respectively. Finally, a reaction mechanism for photocatalytic degradation of methyl orange was proposed.</p>