Teresa Naranjo

The great applications of upconversion nanoparticles (UCNPs) can be further extended by their encapsulation within conjugated porous polymers (CPPs). However, the synthesis of monodisperse core@shell based CPPs upconversion nanohybrids remains a challenge. Herein, we report a simple, general strategy that combines (i) prefunctionalization of UCNPs with polymerizable units, (ii) monomer‐feed control, and (iii) a centrifugation‐based work‐up to ensure anchoring to the inorganic core. This approach enables covalent growth of CPP shells with tunable thickness and low polydispersity. Thus, a BODIPY‐based CPP shell was grown over both core (NaYF ₄ : Yb ³⁺ (20%), Er ³⁺ (2%)) and core‐shell (NaYF ₄ : Yb ³⁺ (20%), Er ³⁺ (2%)@NaYF ₄ ) UCNPs, yielding UC _C @CPP and UC _CS @CPP nanohybrids. Under near‐infrared (NIR) excitation, the UCNP core upconverts light to activate the surrounding CPP shell leading to photocatalytic activity. UC _CS @CPP exhibits a twofold higher photocatalytic activity than UC _C @CPP highlighting the critical role of the NaYF ₄ passivation layer in preserving upconversion efficiency. Our approach overcomes key limitations of previous designs achieving improved photooxidation yields (i.e., 42%) and excellent recyclability. This modular platform provides a robust and versatile route to UC@CPP hybrids for designing NIR‐driven, reactive oxygen species (ROS)‐generating photocatalysts.

This work reports the synthesis and characterization of two di-amino-functionalized dyes based on BODIPY and BOPHY, designed as dual optical sensors for pH and metal ions, with particular selectivity toward Cu²⁺. Owing to the presence of amino groups, both compounds exhibit environment-dependent fluorescence modulation, showing a reversible “on–off” fluorescence behavior in response to acidic conditions and metal coordination. Spectroscopic studies reveal that under acidic pH (below 4), both dyes undergo significant changes in absorption and exhibit enhanced fluorescence, attributed to protonation of the amino groups and a reduction in nitrogen pyramidal inversion. Moreover, both compounds display distinct optical responses upon exposure to various metal salts, with BODIPY showing selective and transient fluorescence activation in the presence of copper sulfate under near-neutral conditions. Detailed analyses suggest the formation of three distinct species during the Cu²⁺ interaction: (I) the native dye, (II) a highly fluorescent intermediate complex, and (III) a non-emissive decomposition product. The kinetics and stability of these species were found to be highly dependent on the solvent environment, particularly its protic/aprotic nature. These findings underscore the potential of these small, structurally simple dyes as efficient dual-function sensors, offering broad applicability in environmental monitoring, biological imaging, and chemical sensing.

Herein, the synthesis of a phenazine‐based ultrananostructured conjugated porous polymer (UN_IEP‐27) is described, using high‐performance microfluidic techniques (HPMT). This approach enables the obtention of small particle sizes, high homogeneity, good dispersibility, large surface areas, and therefore improved processability. The phenazine moiety provides redox‐active sites to the polymer. These features allow the fabrication of high‐quality thin films for photoelectrochemical characterization and, more importantly, significantly enhance the photocatalytic performance of its TiO ₂ hybrid. The hybrid material, UN_IEP‐27@T10 (10 wt.% polymer), reaches hydrogen evolution rates of 4.1 mmol g ⁻ ¹ h ⁻ ¹ (ƺ = 1.52%) under laboratory conditions, and 0.11 mmol g ⁻ ¹ h ⁻ ¹ (ƺ = 0.58%) at solar‐pilot scale representing 51‐fold and 5.5‐fold improvements over bare TiO ₂ , respectively. Moreover, after repeating the experiments under inert atmosphere for consecutive days, the activity increases, reaching up to 4.8 mmol g ⁻ ¹ h ⁻ ¹ (ƺ = 1.76%) and 0.34 mmol g ⁻ ¹ h ⁻ ¹ (ƺ = 1.81%) at lab and pilot scale, respectively. This behavior is attributed to the redox cycling of the phenazine unit, which undergoes reversible transitions between phenazine and its more photoactive form, dihydrophenazine. These results stand among the best reported for conjugated porous polymer (CPP)‐based hybrids for hydrogen photocatalysis.

The development of applicable functional materials currently stands as one of the main challenges in the field of On-Surface Synthesis. In this direction, it is necessary to understand their stability in real conditions, what it is known as bridging the pressure gap. Interestingly, although it is well-established that the on-surface synthesis will be highly influenced by the selected substrate, little is known about the effect of the underlying substrate on the air stability of on-surface synthesized nanostructures. Applying an On-surface Synthesis approach, we report a similar behavior in the synthesis of 1D metal-organic nanostructures based on a BOPHY photoactive molecule on two coinage metal surfaces, Au(111) and Ag(111), but a distinct air stability of these nanostructures when exposed to the atmospheric pressure due to the different catalytic properties of the substrates. In both cases, important comparative conclusions are extracted thanks to a combination of Surface Science characterization techniques with theoretical calculations. This study opens a door to the synthesis of low-dimensional photoactive materials with potential applications, emphasizing the critical role of the substrate not only in the synthesis process but also in the air stability of on-surface synthesized nanostructures.

Here, the use of high‐performance microfluidic techniques (HPMT) is reportedto afford conjugated porous polymer (CPPs) with smaller particle size and narrower particle size dispersion than the obtained by miniemulsion methodology. Specifically, polymers based on BODIPY or BOPHY dyes are synthesized by HPMT conditions and conventional miniemulsion conditions. The polymer textural properties from HPMT are notably improved, giving rise to high‐quality thin films that are photoelectrochemically characterized. Furthermore, hybrid materials of CPPs synthesized by HPMT and TiO₂ inorganic semiconductor revealed enhanced photocatalytic activity in the hydrogen evolution reaction (HER). The most active hybrid UN_IEP‐7@T‐10 photocatalyst, containing 10 wt% polymer loading, achieved a hydrogen evolution rate of 3.10 mmol g⁻¹ h⁻¹ (ƺ = 1.13%), which is threefold higher than that of its non‐nanostructured from bulk synthesis, two‐times greater than its nanostructured by conventional miniemulsion techniques and even surpassed by 39‐times the performance of bare TiO₂. It is noteworthy that both photoluminescence lifetime (τ_PL) and transient lifetime (τ_T) are not affected by the nanoestructuration of CPPs, which agrees with the preservation of the chemical structure by both synthetic methodologies. The employment of HPMT as nanostructuration strategy clearly supports the obtaining of more processable polymers for a wide range of energy applications.

Here we show the improvement in solar driven H₂ production due to the synergy between a novel BOPHY based COF and TiO₂.

Developing highly efficient photocatalysts for artificial photosynthesis is one of the grand challenges in solar energy conversion. Among advanced photoactive materials, conjugated porous polymers (CPPs) possess a powerful combination of high surface areas, intrinsic porosity, cross‐linked nature, and fully π‐conjugated electronic systems. Here, based on these fascinating properties, organic–inorganic hybrid heterostructures composed of CPPs and TiO₂ for the photocatalytic CO₂ reduction and H₂ evolution from water are developed. The study is focused on CPPs based on the boron dipyrromethene (BODIPY) and boron pyrrol hydrazine (BOPHY) families of compounds. It is shown that hybrid photocatalysts are active for the conversion of CO₂ mainly into CH₄ and CO, with CH₄ production 4 times over the benchmark TiO₂. Hydrogen evolution from water surpassed by 37.9‐times that of TiO₂, reaching 200 mmol g_cat⁻¹ and photonic efficiency of 20.4% in the presence of Pt co‐catalyst (1 wt% Pt). Advanced photophysical studies, based on time‐resolved photoluminescence and transient absorption spectroscopy, reveal the creation of a type II heterojunction in the hybrids. The unique interfacial interaction between CPPs and TiO₂ results in longer carriers’ lifetimes and a higher driving force for electron transfer, opening the door to a new generation of photocatalysts for artificial photosynthesis.