Co₃O₄, NiO, and CuO-K₂Ti₆O₁₃ composites were successfully grown in-situ by using an ultrasound-assisted sol–gel method. As a result of the synthesis method, the introduction of the metallic cations into the crystalline structure substituting Ti⁴⁺ or K⁺ cations depending on the case was achieved. For instance, Co²⁺ cations were introduced instead of Ti⁴⁺ cations, while Ni²⁺ and Cu²⁺ were introduced on both sides. The metal-cation introduction between the tunnels favored the growth of K-poor phases as impurities, especially in the CuO loaded K₂Ti₆O₁₃ samples. The presence of these metallic oxides modified the structural and optical properties by forming oxygen vacancies in some samples, favoring the photocatalytic CO₂ reduction in aqueous media to low-weight compounds, such as formaldehyde, methanol, methane, and hydrogen, under visible-light irradiation. Enhanced selectivity of the evolved product, as a result of the metallic cation nature and the formed impurities, was observed. For instance, Co₃O₄ favored the evolution of formaldehyde in the most efficient sample (1 Co-KTO; 453.2 μmol g⁻¹) as a result of the low quantity of impurities present in samples; NiO favored the hydrogen evolution reaction (1 Ni-KTO; 201 μmol g⁻¹), possibly due to the photo-reforming of the organic compounds; and CuO enhanced the methanol and hydrogen production (159.7 and 282 μmol g⁻¹, respectively in 1 Cu-KTO) due to the formation of oxygen vacancies as active sites for the photocatalytic process and reducing the photo-generated charge recombination.

Co ₃ O ₄，NiO和CuO-K ₂ Ti ₆ O ₁₃复合材料通过超声辅助溶胶凝胶法成功地原位生长。作为合成方法的结果，根据情况实现了将金属阳离子引入取代Ti ⁴⁺或K ⁺阳离子的晶体结构中。例如，引入Co ²⁺阳离子代替Ti ⁴⁺阳离子，而在两侧引入Ni ²⁺和Cu ²⁺。隧道之间的金属阳离子引入有利于贫K相作为杂质的生长，特别是在负载CuO的K _2中Ti ₆ O ₁₃样品。这些金属氧化物的存在通过在一些样品中形成氧空位而改变了结构和光学性质，有利于在可见光下将水性介质中的光催化CO ₂还原为低重量化合物，例如甲醛，甲醇，甲烷和氢气辐射。观察到由于金属阳离子性质和所形成的杂质，所生成产物的选择性提高。例如，由于样品中杂质含量低，Co ₃ O ₄促进了最高效样品（1 Co-KTO； 453.2μmolg ^-1）中甲醛的释放；NiO有利于氢释放反应（1 Ni-KTO; 201μmolg^-1），可能由于有机化合物的光重整；由于形成了氧空位作为光催化过程的活性位点并减少了光生电荷的重组，CuO和CuO增强了甲醇和氢气的产生（在1 Cu-KTO中分别为159.7和282μmolg ^-1）。