Microplastics (MPs) are distributed in a wide range of aquatic and terrestrial ecosystems throughout the planet. They are known to adsorb hazardous substances and can transfer them across the trophic web. To eliminate MPs pollution in an environmentally friendly process, we propose using a photocatalytic process that can easily be implemented in wastewater treatment plants (WWTPs). As photocatalysis involves the formation of reactive species such as holes (h⁺), electrons (e⁻), hydroxyl (OH^●), and superoxide ion (O₂^●−) radicals, it is imperative to determine the role of those species in the degradation process to design an effective photocatalytic system. However, for MPs, this information is limited in the literature. Therefore, we present such reactive species’ role in the degradation of high-density polyethylene (HDPE) MPs using C,N-TiO₂. Tert-butanol, isopropyl alcohol (IPA), Tiron, and Cu(NO₃)₂ were confirmed as adequate OH^●, h⁺, O₂^●− and e⁻ scavengers. These results revealed for the first time that the formation of free OH^● through the pathways involving the photogenerated e⁻ plays an essential role in the MPs’ degradation. Furthermore, the degradation behaviors observed when h⁺ and O₂^●− were removed from the reaction system suggest that these species can also perform the initiating step of degradation.

This work presents the photocatalytic degradation of organic pollutants in water with TiO₂ and TiO₂/Ag membranes prepared by immobilising photocatalysts on ceramic porous tubular supports. The permeation capacity of TiO₂ and TiO₂/Ag membranes was checked before the photocatalytic application, showing high water fluxes (≈758 and 690 L m⁻² h⁻¹ bar⁻¹, respectively) and <2% rejection against the model pollutants sodium dodecylbenzene sulfonate (DBS) and dichloroacetic acid (DCA). When the membranes were submerged in the aqueous solutions and irradiated with UV-A LEDs, the photocatalytic performance factors for the degradation of DCA were similar to those obtained with suspended TiO₂ particles (1.1-fold and 1.2-fold increase, respectively). However, when the aqueous solution permeated through the pores of the photocatalytic membrane, the performance factors and kinetics were two-fold higher than for the submerged membranes, mostly due to the enhanced contact between the pollutants and the membranes photocatalytic sites where reactive species were generated. These results confirm the advantages of working in a flow-through mode with submerged photocatalytic membranes for the treatment of water polluted with persistent organic molecules, thanks to the reduction in the mass transfer limitations.

Developing earth‐abundant transition metal catalysts for CO ₂ reduction is a promising approach for sustainable energy conversion. Here, the synthesis and photocatalytic activity of two novel asymmetric iron porphyrin complexes, namely iron 5‐( N ‐benzyloxycarbonyl‐4‐aminophenyl)‐10,15,20‐tris(4‐aminophenyl)porphyrin ( Fe – p – NH ₂ – Cbz ) and iron 5‐( N ‐benzyloxycarbonyl‐4‐aminophenyl)‐10,15,20‐tris(4‐(trimethylammonio)phenyl)porphyrin ( Fe – p – TMA – Cbz ) for visible‐light‐driven CO ₂ reduction to CO and CH ₄ are reported. Under blue light (447 nm) irradiation, Fe – p – NH ₂ – Cbz and Fe – p – TMA – Cbz achieve turnover numbers (TONs) of 20 and 23 for CO, and 6 and 10 for CH ₄ , respectively, using a commercially available organic photosensitizer ( Phenox ), triethylamine (TEA) as sacrificial electron donor and trifluoroethanol (TFE) as proton source. In this reaction conditions, Fe – p – NH ₂ – Cbz and Fe – p – TMA – Cbz demonstrate catalytic activity comparable to its symmetric counterpart iron 5,10,15,20‐tetra(4‐(trimethylammonio)phenyl)porphyrin ( Fe – p – TMA ), previously reported by Prof. Marc Robert's group, achieving a TON of 23 for CO and of 11 for CH ₄ . Isotopic labeling studies using ¹³ CO ₂ confirm that CH ₄ and CO products come from photocatalytic CO ₂ reduction. The results highlight the potential of iron porphyrins as tunable molecular catalysts for photocatalytic CO ₂ reduction beyond two electrons for artificial photosynthesis applications.

Microplastics (MPs) and nanoplastics (NPs) are distributed and transferred among the four major environmental compartments (air, water, soil, and biota) and have been already found in humans, making crucial to develop remediation technologies to tackle this kind pollution. Photocatalysis can be used to eliminate MPs present in contaminated wastewater effluents before their discharge into waterbodies. In this work, several green TiO2-based semiconductors were prepared using the extrapallial fluid (EPF) of Mytilus edulis sea water mussels as doping precursor. The semiconductors were then used as films or powders to photocatalytically degrade polystyrene (PS) NPs and MPs and polyethylene (PE) MPs. It was found that the obtention of green TiO2-based semiconductors with good characteristics for photocatalytic purposes (anatase crystalline phase, presence of porosity, activity in visible light and high surface area) seems not enough to achieve high degradation efficiency. The operational conditions of the reaction system should be also taken into account. For instance, the convenience of using semiconductors in the form of films can be overcome by their limited exposed surface area or the null adsorption of the semiconductor in the MPs particles. Additionally, crystallinity of the semiconductor can be a more determinant factor to take into account when performing photocatalysis of MPs.