A State-of-the-Art of Metal-Organic Frameworks for Chromium Photoreduction vs. Photocatalytic Water Remediation.

Hexavalent chromium (Cr(VI)) is a highly mobile cancerogenic and teratogenic heavy metal ion. Among the varied technologies applied today to address chromium water pollution, photocatalysis offers a rapid reduction of Cr(VI) to the less toxic Cr(III). In contrast to classic photocatalysts, Metal-Organic frameworks (MOFs) are porous semiconductors that can couple the Cr(VI) to Cr(III) photoreduction to the chromium species immobilization. In this minireview, we wish to discuss and analyze the state-of-the-art of MOFs for Cr(VI) detoxification and contextualizing it to the most recent advances and strategies of MOFs for photocatalysis purposes. The minireview has been structured in three sections: (i) a detailed discussion of the specific experimental techniques employed to characterize MOF photocatalysts, (ii) a description and identification of the key characteristics of MOFs for Cr(VI) photoreduction, and (iii) an outlook and perspective section in order to identify future trends.

Chitin/Metal-Organic Framework Composites as Wide-Range Adsorbent.

Composites based on chitin (CH) biopolymer and metal-organic framework (MOF) microporous nanoparticles have been developed as broad-scope pollutant absorbent. Detailed characterization of the CH/MOF composites revealed that the MOF nanoparticles interacted through electrostatic forces with the CH matrix, inducing compartmentalization of the CH macropores that led to an overall surface area increase in the composites. This created a micro-, meso-, and macroporous structure that efficiently retained pollutants with a broad spectrum of different chemical natures, charges, and sizes. The unique prospect of this approach is the combination of the chemical diversity of MOFs with the simple processability and biocompatibility of CH that opens application fields beyond water remediation.

Antibacterial hyaluronic acid/chitosan multilayers onto smooth and micropatterned titanium surfaces.

Bacterial contamination is a critical problem in medical implants, which are preferential sites for bacterial adhesion, leading to infections which can compromise health and immune system of patients. Commercial titanium alloys are the most commonly used materials for permanent implants in contact with bone, and the prevention of infections on their surface is therefore a crucial challenge for orthopaedic and dental surgeons. Thus, the aim of this work is to develop polysaccharide antibacterial coatings onto modified titanium surfaces with different surface topography, in order to act as reservoirs of antibacterial agents. For this, hyaluronic acid/chitosan polyelectrolyte multilayers were successfully developed after acid hydrolysis of Ti-6Al -4 V alloys. Surface modification could be monitorized by XPS spectroscopy, fluorescence confocal microscopy and contact angle measurements. Furthermore, the effect of surface micropatterning on the stability, hydrophilicity, capability to the loading and release of triclosan and the antibacterial properties of prepared multilayers against Staphylococcus aureus were also analysed.