Lignin is the second most abundant biopolymer on the planet. It is a biocompatible, cheap, environmentally friendly and readily accessible material. It has been reported that these biomacromolecules have antimicrobial activities. Consequently, lignin (LIG) has the potential to be used for biomedical applications. In the present work, a simple method to prepare lignin-based hydrogels is described. The hydrogels were prepared by combining LIG with poly(ethyleneglycol) and poly(methyl vinyl ether-co-maleic acid) through an esterification reaction. The synthesis took place in the solid state and can be accelerated significantly (24h vs 1h) by the use of microwave (MW) radiation. The prepared hydrogels were characterized by evaluation of their swelling capacities and with the use of infrared spectroscopy/solid state nuclear magnetic resonance. The prepared hydrogels showed LIG contents ranging between 40% and 24% and water uptake capabilities up to 500%. Furthermore, the hydrophobic nature of LIG facilitated loading of a model hydrophobic drug (curcumin). The hydrogels were capable of sustaining the delivery of this compound for up to 4 days. Finally, the materials demonstrated logarithmic reductions in adherence of Staphylococcus aureus and Proteus mirabilis of up to 5.0 relative to the commonly employed medical material poly(vinyl chloride) (PVC).

A systematic study on the solar photocatalytic hydrogen production (photoreforming) performance of M/TiO₂ (M = Au, Ag, Cu or Pt) using glucose as a model substrate, and further extended to lignocellulose hydrolysates and wastewaters, is herein presented. Three metal (M) co-catalyst loading methods were tested. Variation of the type of metal results in significantly dissimilar H₂ production rates, albeit the loading method exerts an even greater effect in most cases. Deposition-precipitation (followed by hydrogenation) or photodeposition provided better results than classical impregnation (followed by calcination). Interestingly, copper as a co-catalyst performed satisfactorily as compared to Au, and slightly below Pt, thus representing a realistic inexpensive alternative to noble metals. Hydrolysates of either α-cellulose or rice husks, obtained under mild conditions (short thermal cycles at 160 °C), were rich in saccharides and thus suitable as feedstocks. Nonetheless, the presence of inhibiting byproducts hindered H₂ production. A novel photocatalytic UV pre-treatment method was successful to initially remove the most recalcitrant portion of these minor products along with H₂ production (17 µmol g_cat⁻¹ h⁻¹ on Cu/TiO₂). After a short UV step, simulated sunlight photoreforming was orders of magnitude more efficient than without the pre-treatment. Hydrogen production was also directly tested on two different wastewater streams, that is, a municipal influent and samples from operations in a fruit juice producing plant, with remarkable results obtained for the latter (up to 115 µmol g_cat⁻¹ h⁻¹ using Au/TiO₂).

Cu/TiO ₂ photocatalysts promoting H ₂ evolution from acetic acid require exposed Cu(0) surfaces which are reversibly formed by photoreduction.

The use of metal–organic frameworks (MOFs) as templates or precursors in the manufacture of heterogeneous catalysts is highly attractive due to the transfer of MOFs’ inherent porosity and homogeneous metallic distribution to the derived structure. Herein, we report on the preparation of MOF-derived Ru@ZrO₂ catalysts by controlled thermal treatment of zirconium-based MOF UiO-66 with ruthenium moieties. Ru³⁺ (3 or 10 mol%) precursor was added to UiO-66 synthesis and, subsequently, the as-synthesized hybrid structure was calcined in flowing air at different temperatures (400–600 °C) to obtain ZrO₂-derived oxides doped with highly dispersed Ru metallic clusters. The materials were tested for the catalytic photo-thermal conversion of CO₂ to CH₄. Methanation experiments were conducted in a continuous flow (feed flow rate of 5 sccm and 1:4 CO₂ to H₂ molar ratio) reactor at temperatures from 80 to 300 °C. Ru_0.10@ZrO₂ catalyst calcined at 600 °C was able to hydrogenate CO₂ to CH₄ with production rates up to 65 mmol_CH4·g_cat.^–1·h^–1, CH₄ yield of 80% and nearly 100% selectivity at 300 °C. The effect of the illumination was investigated with this catalyst using a high-power visible LED. A CO₂ conversion enhancement from 18% to 38% was measured when 24 sun of visible LED radiation was applied, mainly due to the increase in the temperature as a result of the efficient absorption of the radiation received. MOF-derived Ru@ZrO₂ catalysts have resulted to be noticeably active materials for the photo-thermal hydrogenation of CO₂ for the purpose of the production of carbon-neutral methane. A remarkable effect of the ZrO₂ crystalline phase on the CH₄ selectivity has been found, with monoclinic zirconia being much more selective to CH₄ than its cubic allotrope.

Interpenetrating polymer network (IPN) hydrogels were synthesised using β-cyclodextrin (β-CD) and N-vynil-2-pyrrolidone (NVP) crosslinked with epichlorohydrin and divinylbenzene, respectively, and prepared by four different procedures: simultaneous, sequential, hybrid and a novel one named hybrid-sequential. The IPNs prepared have been characterised by infrared spectroscopy and thermal analysis. The equilibrium swelling in water and the sorption of model substances into the IPNs have also been studied. The model sorbates (1-naphthol, 2-acetylnaphthalene and tannic acid) were selected according to the affinities towards each one of the two constituent polymers. Our studies reveal that these IPNs can be applied for the sorption of substances that can interact with the network by two mechanisms, i.e. inclusion within cyclodextrin cavities and/or via specific interactions with the functional groups present. Besides, due to the complementary character of their constituent polymers, these networks could also serve to retain two substances of different nature such as cetirizine and pseudoephedrine.

Microstructured reactors (MSRs) are especially indicated for highly demanding heterogeneous catalysis due to the small channel dimensions that minimize diffusional limitations and enhance mass and heat transport between the fluid and the catalyst. Herein, we present the fabrication protocol of the fused filament 3D printing of silicone monolithic microreactors based on a multichannel design. Microchannels of 200 to 800 µm in width and up to 20 mm in length were developed following the scaffold-removal procedure using acrylonitrile butadiene styrene (ABS) as the material for the 3D-printed scaffold fabrication, polydimethylsiloxane (PDMS) as the building material, and acetone as the ABS removing agent. The main printing parameters such as temperature and printing velocity were optimized in order to minimize the bridging effect and filament collapsing and intercrossing. Heterogeneous catalysts were incorporated into the microchannel walls during fabrication, thus avoiding further post-processing steps. The nanoparticulated catalyst was deposited on ABS scaffolds through dip coating and transferred to the microchannel walls during the PDMS pouring step and subsequent scaffold removal. Two different designs of the silicone monolithic microreactors were tested for four catalytic applications, namely liquid-phase 2-nitrophenol photohydrogenation and methylene blue photodegradation in aqueous media, lignin depolymerization in ethanol, and gas-phase CO₂ hydrogenation, in order to investigate the microreactor performance under different reaction conditions (temperature and solvent) and establish the possible range of applications.