The present study reports on a simple preparation strategy of a hybrid catalyst, TiO₂/HKUST-1, containing TiO₂ anatase nanoparticles (NPs) with tailored morphology and photocatalytic activity coupled with a porous metal-organic framework (MOF), namely HKUST-1, as an advanced material for the CO₂ photocatalytic reduction. In detail, TiO₂/HKUST-1 catalyst was prepared via an easy slow-diffusion method combined with a step-by-step self-assembly at room temperature. The growth of crystalline HKUST-1 onto titania surface was achieved by functionalizing TiO₂ nanocrystals, with phosphoesanoic acid (PHA), namely TiO₂-PHA, which provides an intimate contact between MOF and TiO₂. The presence of a crystalline and porous shell of HKUST-1 on the TiO₂ surfaces was assessed by a combination of analytical and spectroscopic techniques. TiO₂/HKUST-1 nanocomposite showed a significant efficiency in reducing CO₂ to CH₄ under solar light irradiation, much higher than those of the single components. The role of MOF to improve the photoreduction process under visible light was evidenced and attributed either to the relevant amount of CO₂ captured into the HKUST-1 porous architecture or to the hybrid structure of the material, which affords enhanced visible light absorption and allows an effective electron injection from TiO₂-PHA to HKUST-1, responsible for the photochemical reduction of CO₂.

Three new thiazolo[5,4-d]thiazole-based organic dyes have been designed and synthesized for employment as DSSC sensitizers. Alternation of the electron poor thiazolothiazole unit with two propylenedioxythiophene (ProDOT) groups ensured very intense light absorption in the visible region (ε up to 9.41 × 10⁴ M⁻¹ cm⁻¹ in THF solution). The dyes were particularly suitable for application in transparent and opaque thin-layer DSSCs (TiO₂ thickness: 5.5–6.5 μm, efficiencies up to 7.71%), thus being good candidates for production of solar cells under simple fabrication conditions.

In this paper, we present the design and synthesis of three organic dyes specially developed for the fabrication of dye-sensitized solar cells for application in greenhouses cladding. The dyes (BTD-DTP1–3) are based on a benzothiadiazole (BTD)–dithienopyrrole (DTP) scaffold, and were assembled by using direct arylation reactions, allowing significant reduction of the number of synthetic and purification steps compared to classic cross-coupling procedures. Thanks to their structural design, the dyes absorb light in the green part of the visible spectrum while allowing good transmittance in the red and blue regions, thus ensuring high compatibility with light absorption by plants. Dye-sensitized solar cells built with the three dyes provided energy conversion efficiencies (ECEs) comparable or even superior to those obtained with the reference Ru-based dye N719, especially when using a thin and semitransparent TiO₂ layer (up to 8.77%). The photovoltaic performances are discussed considering the need to reach the best compromise between good ECE values and high levels of weighed transparency against the main plant photoreceptors.