We report the synthesis of a highly active and stable metal‐organic framework derived Ni‐based catalyst for the photothermal reduction of CO2 to CH4. Through the controlled pyrolysis of MOF‐74 (Ni), ...the nature of the carbonaceous species and therefore photothermal performance can be tuned. CH4 production rates of 488 mmol g−1 h−1 under UV‐visible‐IR irradiation are achieved when the catalyst is prepared under optimized conditions. No particle aggregation or significant loss of activity were observed after ten consecutive reaction cycles or more than 12 hours under continuous flow configuration. Finally, as a proof‐of‐concept, we performed an outdoor experiment under ambient solar irradiation, demonstrating the potential of our catalyst to reduce CO2 to CH4 using only solar energy.
A Ni‐based catalyst derived from Ni‐MOF‐74 was synthesized and studied for the photothermal methanation reaction. The catalyst shows high performance for CH4 production under visible‐IR irradiation. The catalyst also shows high stability and excellent recyclability after several consecutive reaction cycles.
Covalent postsynthetic modification (PSM) of metal–organic frameworks (MOFs) has attracted much attention due to the possibility of tailoring the properties of these porous materials. Schiff-base ...condensation between an amine and an aldehyde is one of the most common reactions in the PSM of MOFs. Here, we report the use of the spray drying technique to perform this class of organic reactions, either between discrete organic molecules or on the pore surfaces of MOFs, in a very fast (1–2 s) and continuous way. Using spray drying, we show the PSM of two MOFs, the amine-terminated UiO-66-NH2 and the aldehyde-terminated ZIF-90, achieving conversion efficiencies up to 20 and 42%, respectively. Moreover, we demonstrate that it can also be used to postsynthetically cross-link the aldehyde groups of ZIF-90 using a diamine molecule with a conversion efficiency of 70%.
Herein, we describe a new class of porous composites comprising metal–organic framework (MOF) crystals confined in single spherical matrices made of packed covalent‐organic framework (COF) ...nanocrystals. These MOF@COF composites are synthesized through a two‐step method of spray‐drying and subsequent amorphous (imine‐based polymer)‐to‐crystalline (imine‐based COF) transformation. This transformation around the MOF crystals generates micro‐ and mesopores at the MOF/COF interface that provide far superior porosity compared to that of the constituent MOF and COF components added together. We report that water sorption in these new pores occurs within the same pressure window as in the COF pores. Our new MOF@COF composites, with their additional pores at the MOF/COF interface, should have implications for the development of new composites.
Open pore remedy: A new class of porous composites comprising metal–organic framework (MOF) crystals confined in single spherical matrices made of packed covalent‐organic framework (COF) nanocrystals is described. These MOF@COF composites show the formation of micro‐ and mesopores at the MOF/COF interface that provide superior porosity compared to that of the constituent MOF and COF components added together.
Adsorptive heat transformation systems such as adsorption thermal batteries and chillers can provide space heating and cooling in a more environmental friendly way. However, their use is still ...hindered by their relatively poor performances and large sizes due to the limited properties of solid adsorbents. Here, the spray‐drying continuous‐flow synthesis of a new type of solid adsorbents that results from combining metal‐organic frameworks (MOFs), such as UiO‐66, and hygroscopic salts, such as CaCl2 has been reported. These adsorbents, commonly named as composite salt in porous matrix (CSPM) materials, allow improving the water uptake capabilities of MOFs while preventing their dissolution in the water adsorbed; a common characteristic of these salts due to the deliquescence effect. It is anticipated that MOF‐based CSPMs, in which the percentage of salt can be tuned, are promising candidates for thermal batteries and chillers. In these applications, it is showed that a CSPM made of UiO‐66 and CaCl2 (38% w/w) exhibits a heat storage capacity of 367 kJ kg−1 , whereas a second CSPM made of UiO‐66 and CaCl2 (53% w/w) shows a specific cooling power of 631 W kg−1 and a coefficient of performance of 0.83, comparable to the best solid adsorbents reported so far.
A new type of composite salt in porous matrix adsorbents that results from combining metal‐organic frameworks (MOFs) and hygroscopic salts (CaCl2, LiCl) has been synthesized by spray‐drying continuous‐flow method. The applicability of these MOF‐based CSPMs has been demonstrated for potential applications in thermal batteries and refrigerator systems, demonstrating high capacity and energetic efficiency.
Pollution of water with heavy metals is a global environmental problem whose impact is especially severe in developing countries. Among water-purification methods, adsorption of heavy metals has ...proven to be simple, versatile, and cost-effective. However, there is still a need to develop adsorbents with a capacity to remove multiple metal pollutants from the same water sample. Herein, we report the complementary adsorption capacities of metal–organic frameworks (here, UiO-66 and UiO-66-(SH)2) and inorganic nanoparticles (iNPs; here, cerium-oxide NPs) into composite materials. These adsorbents, which are spherical microbeads generated in one step by continuous-flow spray-drying, efficiently and simultaneously remove multiple heavy metals from water, including As(III and V), Cd(II), Cr(III and VI), Cu(II), Pb(II), and Hg(II). We further show that these microbeads can be used as a packing material in a prototype of a continuous-flow water treatment system, in which they retain their metal-removal capacities upon regeneration with a gentle acidic treatment. As proof-of-concept, we evaluated these adsorbents for purification of laboratory water samples prepared to independently recapitulate each of two strongly polluted rivers: the Bone (Indonesia) and Buringanga (Bangladesh) rivers. In both cases, our microbeads reduced the levels of all the metal contaminants to below the corresponding permissible limits established by the World Health Organization (WHO). Moreover, we demonstrated the capacity of these microbeads to lower levels of Cr(VI) in a water sample collected from the Sarno River (Italy). Finally, to create adsorbents that could be magnetically recovered following their use in water purification, we extended our spray-drying technique to simultaneously incorporate two types of iNPs (CeO2 and Fe3O4) into UiO-66-(SH)2, obtaining CeO2/Fe3O4@UiO-66-(SH)2 microbeads that adsorb heavy metals and are magnetically responsive.
Metal–organic frameworks (MOFs) usually require meticulous removal of the solvent molecules to unlock their potential porosity. Herein, we report a novel one-step method for activating MOFs based on ...the photothermal effect induced by directly irradiating them with a UV–vis lamp. The localized light-to-heat conversion produced in the MOF crystals upon irradiation enables a very fast solvent removal, thereby significantly reducing the activation time to as low as 30 min and suppressing the need for time-consuming solvent-exchange procedures and vacuum conditions. This approach is successful for a broad range of MOFs, including HKUST-1, UiO-66–NH2, ZIF-67, CPO-27–M (M = Zn, Ni, and Mg), Fe–MIL-101–NH2, and IRMOF-3, all of which exhibit absorption bands in the light emission range. In addition, we anticipate that this photothermal activation can also be used to activate covalent organic frameworks (COFs).
The direct utilization of light to drive chemical reactions has been considered a promising approach to decarbonizing the chemical industry and storing solar energy in the form of chemical bonds. In ...this regard, photo‐thermal catalysis has emerged as a bright strategy due to the combination of thermal and non‐thermal contributions of sunlight. This enables the whole exploitation of the solar spectrum providing localized heating and thus an enhancement in the productivity rates. In this scenario, MOFs and MOFs‐derived materials offer great opportunities for the rational design of new photo‐thermal catalysts. In this review, we describe the different types of photo‐thermal systems, with a particular consideration on the mechanisms. Further, we describe the recent advances of MOF and MOF‐derived materials as photo‐thermal catalysts for different catalytic reactions, including organic transformations, pollutant degradation or CO2 hydrogenations. Lastly, we present our opinion on the future challenges and perspectives in the field.
Photo‐thermal catalysis benefits from the synergistic combination of the thermal and non‐thermal contributions of sunlight. In this regard, metal‐organic frameworks and their derived materials are promising candidates as photo‐thermal catalysts owing to their unique properties including high porosity, enhanced light absorption or improved thermal conductivity.
Metal‐organic frameworks (MOFs) built up from connecting M‐XF6 pillars through N‐donor ligands are among the most attractive adsorbents and separating agents for CO2 and hydrocarbons today. The ...continuous, one‐step spray‐drying synthesis of several members of this isoreticular MOF family varying the anionic pillar (XF6=SiF62− and TiF62−), the N‐donor organic ligand (pyrazine and 4,4′‐bipyridine) and the metal ion (M=Co, Cu and Zn) is demonstrated here. This synthetic method allows them to be obtained in the form of spherical superstructures assembled from nanosized crystals. As confirmed by CO2 and N2 sorption studies, most of the M‐XF6‐based MOFs synthesised through spray‐drying can be considered “ready‐to‐use” sorbents as they do not need additional purification and time consuming solvent exchange steps to show comparable porosity and sorption properties with the bulk/single‐crystal analogues. Stability tests of nanosized M‐SiF6‐based MOFs confirm their low stability in most solvents, including water and DMF, highlighting the importance of protecting them once synthesised. Finally, for the first time it was shown that the spray‐drying method can also be used to assemble hydrogen‐bonded open networks, as evidenced by the synthesis of MPM‐1‐TIFSIX.
Dry run: Industry‐derived spray drying technology has been successfully applied to synthesise one of the most promising subclass of metal‐organic frameworks, M‐XF6 based MOFs, which exhibit exceptional CO2 sorption properties.
The ingestion of gluten-containing foods can cause wheat-related disorders in up to 15% of wheat consuming populations. Besides the role of gluten, α-amylase/trypsin inhibitors (ATI) have recently ...been identified as inducers of an innate immune response via toll-like receptor 4 in celiac disease and non-celiac wheat sensitivity. ATI are involved in plant self-defense against insects and possibly in grain development. Notably, they are largely resistant to gastrointestinal proteases and heat, and their inflammatory activity affects not only the intestine, but also peripheral organs. The aim of this study was to understand the changes of ATI throughout the sourdough and yeast-fermented bread-making processes. ATI tetramers were isolated, fluorescein-labelled, and added to a mini-dough bread-making system. When the pH decreased below 4.0 in sourdough fermentation, the ATI tetramers were degraded due to the activation of aspartic proteases, whilst in yeast fermentation, ATI tetramers remained intact. The amylase inhibitory activity after sourdough fermentation decreased significantly, while the concentration of free thiol groups increased. The glutathione reductase activity of Fructilactobacillus sanfranciscensis did not contribute to the reduction of ATI tetramers. Compared to the unfermented wheat, sourdough fermentation was able to decrease the release of pro-inflammatory cytokines monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor alpha (TNF-α) in quantitative ATI extracts added to the human monocytic cell line THP-1. The current data suggest that sourdough fermentation can degrade ATI structure and bioactivity, and point to strategies to improve product development for wheat sensitivity patients.
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