Hierarchical Assembly of a Micro- and Macroporous Hydrogen-Bonded Organic Framework with Tailored Single-Crystal Size

Porous organic molecular materials represent an emergent field of research in Chemistry and Materials Science due to their unique combination of properties. To enhance their performance and expand the number of applications, the incorporation of hierarchical porosity is required, as exclusive microporosity entails several limitations. However, the integration of macropores in porous organic molecular materials is still an outstanding challenge. Herein, we report the first example of a hydrogen-bonded organic framework (MM-TPY) with hierarchical skeletal morphology, containing stable micro- and macroporosity. The crystal size, from micro to centimetre scale, can be controlled in a single step without using additives or templates. The mechanism of assembly during the crystal formation is compatible with a skeletal crystal growth. As proof of concept, we employed the hierarchical porosity as a platform for the dual, sequential and selective co-recognition of molecular species and microparticles.J.F.-S. thanks “Ramón y Cajal“ program (RYC2019-02794-I), MINECO (Spain) (Projects PID2019−104778GB−I00 and Excellence Unit “Maria de Maeztu” CEX2019−000919−M) and Generalitat Valenciana (SEJI/2020/034). E.V.R.F. thanks Ministerio de Ciencia e innovación (PID2020-116998RB-I00) and Ministerio de Educación y Formación Profesional (PRX21/00407)

Direct monitoring of the potassium charge carrier in Prussian blue cathodes using potassium K-edge X-ray absorption spectroscopy †

Prussian blue is widely utilized as a cathode material in batteries, due to its ability to intercalate alkaline metal ions, including potassium. However, the exact location of potassium or other cations within the complex structure, and how it changes as a function of cycling, is unclear. Herein, we report direct insight into the nature of potassium speciation within Prussian blue during cyclic voltammetry, via operando potassium K-edge X-ray Absorption Near Edge Structure (XANES) analysis. Clear and identifiable spectra are experimentally differentiated for the fully intercalated (fully reduced Fe2+FeII Prussian white), partially intercalated (Prussian blue; Fe3+FeII), and free KNO3(aq) electrolyte. Comparison of the experiment with simulated XANES of theoretical structures indicates that potassium lies within the channels of the Prussian blue structure, but is displaced towards the periphery of the channels by occluded water and/or structural water present resulting from [Fe(CN)6]4− vacancies. The structural composition from the charge carrier perspective was monitored for two samples of differing crystallite size and electrochemical stability. Reproducible potassium XANES spectral sequences were observed for large crystallites (ca. 100 nm) of Prussian blue, in agreement with retention of capacity; in contrast, the capacity of a sample with small crystallites (ca. 14 nm) declined as the potassium became trapped within the partially intercalated Prussian blue. The cause of degradation could be attributed to a significant loss of [Fe(CN)6]–[Fe(NC)6] ordering and the formation of a potassium-free non-conducting ferrihydrite phase. These findings demonstrate the potential of XANES to directly study the nature and evolution of potassium species during an electrochemical process

Avaliação do perfil metabólico de vacas da raça Holandesa durante o período de transição

O período de transição é um momento de grande desafio para vacas de aptidão leiteira, uma vez que, a maioria dos problemas metabólicos ocorre nesta fase podendo prejudicar toda a expectativa de produção durante a lactação, resultando em impacto econômico significativo para fazendas de produção de leite. Este trabalho teve como objetivo avaliar o perfil metabólico de vacas da raça Holandesa durante o período de transição. Doze vacas Holandesas foram avaliadas, três semanas pré-parto até três semanas pós-parto, em sistema free-stall, localizado em Inhaúma, Minas Gerais, no período de outubro a dezembro de 2012. Avaliou-se o perfil metabólico através da concentração sérica de ácidos graxos não esterificados (AGNE), beta hidroxibutirato (BHBA), colesterol (COLES), proteína total (PT), albumina (ALB), cálcio, fósforo, magnésio bem como a atividade sérica das enzimas aspartato transaminase (AST) e lactato desidrogenase (LDH). As concentrações séricas de AGNE e BHBA foram diferentes entre o pré-parto e pós-parto (p0,05) no período avaliado. A atividade enzimática de AST e LDH foram maiores no período pós-parto (p<0,05). A avaliação do perfil metabólico é uma importante ferramenta de monitoramento e, na situação estudada, demonstrou alterações do perfil energético das vacas entre os períodos pré e pós-parto, relacionadas provavelmente a diminuição da ingestão de alimentos. A luz dos resultados do perfil metabólico, o rebanho avaliado possui pequeno risco para a ocorrência de enfermidades no pós-parto relacionadas ao período de transiçã