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In comparison with fully activated MIL-53(Al)-TDC, MeOH@MIL-53(Al)-TDC shows a 39% higher SO2 capture capacity.

Six polyheterocycles were studied in vitro against human SARS-CoV-2 finding that one of them exhibited significant activity at initial infection stages, showing prophylactic potential. A second one showed both, prophylactic and therapeutic activity.

The SO

More than 60 years have passed since I. Ugi synthesized the first α-amidoamides in one experimental step involving a combination of aldehydes, amines, carboxylic acids and isocyanides, a multicomponent reaction (MCR) known later as the Ugi four-component reaction (U-4CR), in honor of the pioneer of the modern MCR-based organic synthesis. Then, a broad variety of valued molecules (α-aminoamides) in various fields of science and technology have been synthesized via a three-component version of the Ugi reaction (U-3CR or truncated Ugi reaction), which makes use of a carbonylic component (aldehydes or ketones), amines and isocyanides. Moreover, some variants of the U-3CR have been developed, including its combinations with further processes such as functionalizations, condensations, cross couplings, cyclizations, ring openings, rearrangements, and so on. Also, some robust computational calculations for understanding the energy profiles of Ugi-type 3CR have been performed. All these topics are in the scope of the present review, which covers selected works mainly from the last decade, focusing on relevant contributions to heterocyclic chemistry, and especially on novel and complex reaction mechanisms. The manuscript has been categorized by the name/type reaction approach, aiming to give readers novel insights for further investigations.

Metal–organic frameworks (MOFs) have become the most promising molecular sponges to capture gases contributing to the greenhouse effect, e.g. CO2, due to various desirable features such as tuneable pore shapes, sizes and functionalities, a great surface area, resistance to harsh conditions (wide ranges of pH, temperatures, humidity, etc.), ease of their preparation, and in most cases, a high degree of recovery. Thus, despite many MOFs adsorbing extensive amounts of CO2 in their pristine form, it has been demonstrated that their uptake capability can be considerably enhanced when they are post-synthetically modified by the confinement of molecules with different polarities, as a result of new physical–chemical interactions between the pre-confined species and the CO2 molecules within their cavities, for example, via the bottleneck effect, H-bonds and/or even π–π stacking interactions. Thus, this review covers selected studies, mainly from the last five years, highlighting the most significant advances on the CO2 enhanced uptake performance of selected MOFs with pre-adsorbed polar (water, alcohols, and amines) and non-polar (toluene and benzene) molecules, as well as some interesting findings from robust computational calculations behind understanding the nature of such host–guest interactions, with the latter one being a practical and useful tool in the research field.

Capture, storage and subsequent controlled release or transformation of sulfur dioxide (SO

Metal–organic frameworks (MOFs) are some of the most interesting and promising candidates to sequester toxic H2S and SO2 gases. MOFs show interesting advantages over classic porous materials due to...

The toluene adsorption properties of InOF-1 are studied along with the confinement of small amounts of this non-polar molecule revealing a 1.38-fold increase in CO2 capture, from 5.26 wt% under anhydrous conditions to 7.28 wt% with a 1.5 wt% of pre-confined toluene at 298 K. The InOF-1 affinity towards toluene was experimentally quantified by ΔHads (−46.81 kJ mol−1). InOF-1 is shown to be a promising material for CO2 capture under industrial conditions. Computational calculations (DFT and QTAIM) and DRIFTs in situ experiments provided a possible explanation for the experimental CO2 capture enhancement by showing how the toluene molecule is confined within InOF-1, which constructed a “bottleneck effect”.

The enhancement of CO2 capture due to the confinement of polar molecules within InOF-1 was previously demonstrated. In particular, the presence of MeOH produced 1.30-fold increase in the total CO2 capture. This was explained before with the presence of hydrogen bonds. However, a detailed analysis of the hydrogen bonds among μ2-OH functional groups, MeOH molecules and CO2 molecules was not elucidated; moreover, the possible mechanisms that could explain the enhancement of the capture were also not explained. In this investigation, the density functional theory (DFT) periodic calculations and experimental in situ DRIFTS results allowed us to postulate four plausible CO2 adsorption mechanisms for MeOH-functionalised InOF-1, which described the hydrogen bonds and rationalised the nature of the CO2 capture enhancement.

International audience; The MOF-type MFM-300(Sc) is demonstrated to be an optimal adsorbent for SO2 capture combining high uptake, good stability and excellent cyclability involving a remarkable facile regeneration at room temperature. Interestingly, this MOF shows a drastic enhancement on its SO2 uptake by 40% when a small amount of ethanol is preliminary adsorbed.

The 2-propanol (i-PrOH) adsorption properties of InOF-1 are investigated along with the confinement of small amounts of this alcohol to enhance the CO2 capture for i-PrOH@InOF-1 (1.25-fold improvement compared to pristine InOF-1). InOF-1 exhibited a high affinity towards i-PrOH, experimentally quantified by ΔHads (−55 kJ mol−1), and DFT geometry optimisations showed strong hydrogen bonding between O(i-PrOH) and H(μ2-OH). Quantum chemical models demonstrated that the CO2 capture increase for i-PrOH@InOF-1 was due to a decrease in the void surface of InOF-1 (bottleneck effect), and the formation of essential hydrogen bonds of CO2 with i-PrOH and with the hydroxo functional group (μ2-OH) of InOF-1.

The partial functionalisation of MIL-101(Cr) with fluorine was successfully achieved, for the first time, with 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylate (BDC-4F) affording MIL-101(Cr)-4F(1%). As a result of the functionalisation the acidity of the metal centres for MIL-101(Cr)-4F(1%) was enhanced, which was measured by cyclic voltammetry. The resulting adsorption properties of the new material were explored and compared to those of MIL-101(Cr). H2O sorption experiments demonstrated an augmented hydrophobicity of the material due to the incorporation of fluorine atoms. CO2 adsorption experiments exhibited an augmented CO2 interaction energy (ΔH) for MIL-101(Cr)-4F(1%). The diffusion time constant for CO2 showed a higher CO2 mobility inside the pores of MIL-101(Cr) than in MIL-101(Cr)-4F(1%), which was also associated with a higher selectivity (α) of MIL-101(Cr)-4F(1%) towards CO2. O2 sorption isotherms of MIL-101(Cr)-4F(1%), at a high pressure (up to 90 bar), demonstrated O2 uptakes among the highest values reported for a MOF material. H2 adsorption isotherms exhibited, at low pressures, higher H2 uptakes for the fluorine functionalised material. This was attributed to dipolar interactions of H2 molecules with the fluorine atoms and corroborated by the calculation of ΔH for H2. 129Xe NMR experiments were used to investigate the atypical pore-surface electron density of MIL-101(Cr)-4F(1%), demonstrating a huge effect of the polarising power of the fluorine atoms on the highly polarisable Xe atoms. Finally, the capture of I2 and H2S on MIL-101(Cr)-4F(1%) showed considerably higher values in comparison to MIL-101(Cr). This was attributed to the high dipolarity and polarisability of the fluorinated pores.

The CO2 capture properties of CAU-10 were investigated at different relative humidity conditions. The total CO2 capture increased 1.3-fold from 5.4 wt% under anhydrous conditions to 7.3 wt% at 5% RH and 303 K. The hydrophobicity of the pore provides to the material CAU-10 a ‘self-regulated’ water content, which promoted the enhancement of the CO2 uptake in the low relative humidity domain (3–20% HR), resulting in a ‘constant’ uptake in this whole range. Adsorption–desorption cycles experiments on a hydrated sample, confirmed the retention of the CO2 uptake capacity under humid conditions. CAU-10 showed to be a promising material for CO2 capture under industrial relevant conditions.

We herein report the synthesis and characterization of six α,β-unsaturated dicarboxylic acid ligands with different phenyl spacers, and two ligands with a biphenyl and anthraquinone spacers. All these dimaleamic acids were synthesized in 16 to 99% yields via a base-catalyzed maleimide ring opening in water (ligand 2), or by a di-N-acylation from the corresponding diamines and maleic anhydride in acetic acid (ligands 4, 6, 8, 10, 12, 14 and 16). These reactions were performed using green solvents, while requiring minimal work up procedures, making them suitable alternatives to access these types of bidentate ligands quickly, which can be used to fabricate new metal-organic frameworks (MOFs).

The fluorescent properties of MIL-53(Al)-TDC are drastically changed due to the presence of iodine, even in small quantities, as a result of an energy transfer process from the host material (MIL-53(Al)-TDC) to the guest molecule (I2). While MIL-53(Al)-TDC's emission spectrum shows a weak and broad band, after I2 adsorption, it exhibits well-resolved and long-lasting emission lines, which could be exploited for iodine detection. Density Functional Theory periodical calculations demonstrated that in the most stable MIL-53(Al)-TDCI2 configuration, the I2 molecule is bonded mainly by an O-HI hydrogen bond. The QTAIM showed that other non-covalent interactions also provided stability to MIL-53(Al)-TDCI2. The electrostatic potential analysis indicated that the I2 molecule adsorption occurs by a combination of specific interactions with a strong electrostatic contribution and weak interactions. These results postulate fluorescent MIL-53(Al)-TDC as an efficient I2 detector (potentially for radioactive I2), using a simple fluorimetric test.

Sulfadiazine (SDZ), a bacteriostatic agent, was hosted in a metal–organic framework, specifically in MIL-53(Al) and modified-zinc MIL-53(Al,Zn). Materials were characterized structural, and texturally. Both hosts loaded sulfadiazine but they were differenced regarding the release of sulfadiazine. The presence of zinc plays a significant role to the modulation of sulfadiazine–MOF interactions. Release of sulfadiazine from sulfadiazine@MOFs was monitored in vitro and ex vivo conditions. A kinetic release model is proposed for in vitro sulfadiazine release. Remarkably, the materials did not show cytotoxicity against eukaryote cells.

The metal-organic framework (MOF)-type MFM-300(Sc) exhibits a combined physisorption and chemisorption capture of H2S, leading to a high uptake (16.55 mmol g-1) associated with high structural stability. The irreversible chemisorbed sulfur species were identified as low-order polysulfide (n = 2) species. The isostructural MFM-300(In) was demonstrated to promote the formation of different polysulfide species, paving the way toward a new methodology to incorporate polysulfides within MOFs for the generation of novel MOF-lithium/sulfur batteries.

International audience; H2O and cyclohexane adsorption properties and the CO2 and CO capture capability of the microporous material Fe(pz)[Pt(CN)4] were examined. This 3D coordination polymer retained its crystallinity and structural stability after all adsorption–desorption experiments (demonstrated by PXRD and BET surface area). Thus, the total water uptake was equal to 14.6 wt % (8.12 mmol g–1) at 90% P/P0, and in comparison to the adsorption of cyclohexane, Fe(pz)[Pt(CN)4] demonstrated a relatively high degree of hydrophilicity. The total cyclohexane uptake of 0.28 mmol g–1, which in comparison to the total water uptake value of 8.12 mmol g–1, corroborated such hydrophilic behavior. Additionally, the CO2 capture was equal to 9.3 wt % for activated Fe(pz)[Pt(CN)4], a higher value in comparison to other lead MOFs such as NOTT-400 (4.4 wt %), despite the fact that the latter exhibits a larger BET surface area (1356 m2 g–1) than Fe(pz)[Pt(CN)4] (BET = 431 m2 g–1). When the CO2 capture capability was measured on a partially water saturated Fe(pz)[Pt(CN)4] sample, we observed a weight gain from 11.7 wt % (only water uptake) to 14.1 wt % (water + CO2). This weight increment (2.4 wt %) was attributed to the oversolubility of CO2. The CO capture on Fe(pz)[Pt(CN)4] showed a total uptake of 4.7 mmol/g after only 20 min, a result comparable to those for MOFs with much higher BET surface areas, such as MOF-74(Mg) (BET = 1957 m2 g–1; 4.4 mmol g–1). Finally, in situ DRIFT experiments exhibited the coordination of CO with open Pt(II) metal sites.

The metal-organic framework (MOF)-type MFM-300(Sc) exhibits a combined physisorption and chemisorption capture of H

The structure transformation of Mg-CUK-1 due to the confinement of H2O molecules was investigated. Powder X-ray diffraction (PXRD) patterns were collected at different H2O loadings and the cell parameters of the H2O-loaded Mg-CUK-1 material were determined by the Le Bail strategy refinements. A bottleneck effect was observed when one hydrogen-bonded H2O molecule per unit cell (18% relative humidity (RH)) was confined within Mg-CUK-1, confirming the increase in the CO2 capture for Mg-CUK-1.

The confinement of small amounts of benzene in InOF-1 (Bz@InOF-1) shows a contradictory behavior in the capture of CO2 and SO2. While the capture of CO2 is increased 1.6 times, compared to the pristine material, the capture of SO2 shows a considerable decrease. To elucidate these behaviors, the interactions of CO2 and SO2 with Bz@InOF-1 were studied by DFT periodical calculations postulating a plausible explanation: (a) in the case of benzene and CO2, these molecules do not compete for the preferential adsorption sites within InOF-1, providing a cooperative CO2 capture enhancement and (b) benzene and SO2 strongly compete for these preferential adsorption sites inside the MOF material, reducing the total SO2 capture.

The confinement of small amounts of benzene in InOF-1 (Bz@InOF-1) shows a contradictory behavior in the capture of CO2 and SO2. While the capture of CO2 is increased 1.6 times, compared to the pristine material, the capture of SO2 shows a considerable decrease. To elucidate these behaviors, the interactions of CO2 and SO2 with Bz@InOF-1 were studied by DFT periodical calculations postulating a plausible explanation: (a) in the case of benzene and CO2, these molecules do not compete for the preferential adsorption sites within InOF-1, providing a cooperative CO2 capture enhancement and (b) benzene and SO2 strongly compete for these preferential adsorption sites inside the MOF material, reducing the total SO2 capture.

The synthesis and characterization of three new bis 1-substituted 1H-tetrazoles are described. Two products were synthesized in a single step via a direct heterocyclization of primary amines, methyl orthoester (trymethyl orthoformate), and sodium azide in 30% and 91% yields, respectively. Besides, another one was prepared via a three-step synthetic strategy: SNAr (32%), nitro-group reduction (66%), and primary amine heterocyclization (83%), yielding 18%, overall. The aim behind the synthesis of new tetrazole-containing products is to construct novel MOF-like structures to evaluate their gas capture properties (CO2, CO, and SO2) under relative humidity conditions.

A greener synthesis of Cu-MOF-74 was obtained, for the first time, in methanol as the unique solvent and at room temperature. Full characterisation of the MOF material showed its purity and also its nanocrystalline nature. Complete activation (150 °C for 1 h and 10-3 bar) of Cu-MOF-74 afforded unsaturated Cu metal sites and this was corroborated by in situ DRIFT spectroscopy. The access to these Cu open metal sites was tested for the catalytic transformation of trans-ferulic acid to vanillin (yield of 71% and 97% selectivity) and a plausible catalytic reaction mechanism was postulated based on quantum chemical calculations.

EtOH sorption properties were investigated in MIL-53(Al)-TDC and found a strong interaction between EtOH and the MOF material (ΔHads = 69.6 kJ mol−1). CO2 capture was enhanced upon confining small amounts of H2O. Upon confining small amounts of EtOH however, the CO2 uptake was not improved. The difference in CO2 uptake with EtOH and H2O was rationalised using computational calculations. The analysis of the quantum theory of atoms in molecules (QTAIM) showed a covalent interaction between a MOF model and confined molecules (EtOH and H2O), and no difference in the hydrogen bonds between confined molecules and CO2.

The bottleneck effect of confined N,N-dimethylformamide (DMF) molecules was observed in InOF-1 for the first time: CO2 capture was remarkably enhanced in samples of as-synthesized InOF-1, thermally activated in such a way that a small residual amount of DMF molecules remained confined within the pores (DMF@InOF-1). Dynamic CO2 adsorption experiments on DMF@InOF-1 exhibited a CO2 capture of 8.06 wt % [1.5-fold higher than that of a fully activated InOF-1 (5.24%)]. DMF@InOF-1 can reversibly adsorb/desorb 8.09% CO2 with no loss of CO2 capacity after 10 cycles, and the desorption is accomplished by only turning the CO2 flow off. Static CO2 adsorption experiments (at 196 K) demonstrated a 1.4-fold CO2 capture increase (from 5.5 mmol·g–1, fully activated InOF-1, to 7.5 mmol·g–1, DMF@InOF-1). Therefore, these CO2 capture properties are the result of the presence of residual-confined DMF molecules within the InOF-1 framework and their interactions via a very strong hydrogen bond with the In2(μ-OH) groups, which p...

Metal–organic frameworks (MOFs) are one of the most promising candidates for CO2 capture due to their sorption selectivity towards CO2. The optimisation of the physical–chemical interactions between MOFs and CO2 molecules is the key to further amplification of CO2 capture. An emerging technology for CO2 capture is the construction of hybrid adsorbent MOFs via confinement of water inside the pores. This review article describes the recent progress in this field. Indeed, the pre-adsorption of small quantities of water within the micropores of MOF materials (constructed with hydroxo functional groups, μ2-OH) provides a positive impact on the overall CO2 capture. We anticipate that the current review article can offer useful information on the significant developments made for the enhancement of CO2 capture by confining water (and other solvents) within the pores of MOFs, which is a very promising technology for real-world applications, where MOF materials could be capable of serving as next-generation CO2 capture systems.