Room-temperature synthesis of bimetallic ZnCu-MOF-74 as an adsorbent for tetracycline removal from an aqueous solution.

The novel bimetallic MOF, ZnCu-MOF-74, has been evaluated for the remediation of tetracycline-contaminated water. ZnCu-MOF-74 was obtained at room temperature, avoiding high pressure and temperature. ZnCu-MOF-74 exhibited chemical stability in the 4-8 pH range. The adsorption result analysis was described using the Elovich kinetic model and the Langmuir adsorption isotherm, suggesting a physicochemical process. The maximum adsorption capacity was estimated at 775.66 mg g-1. The pH of the solution and the presence of ions such as NO3-, SO42-, Na+, Mg2+, Cl-, and Ca2+ had no influence on the removal of tetracycline. In addition, π-interactions and metal complexation were proposed as possible adsorption mechanisms through FT-IR and XPS. ZnCu-MOF-74 showed outstanding cyclability performance, preserving its adsorption capacity after 4 adsorption-desorption cycles, besides exhibiting chemical stability, proving the benefits of applying ZnCu-MOF-74 in the water treatment process.

APTES functionalization in SBA-15: the effect on SO2 capture and detection applications.

The development of adsorbents for air pollutant remediation and effective monitoring is of interest. Then, the effect of the APTES functionalization ratio on the impact of the adsorption and detection of SO2 molecules was evaluated. The higher APTES functionalization material (SBA-15_6.1APTES) shows a high uptake of 1.15 mmol g-1 at 0.001 bar and 298 K. Fluorescence, time-resolved photoluminescence, and quantum yield experiments revealed a turn-on effect specifically for SO2 molecules, indicating high selectivity, suggesting host-to-guest energy transfer. Attractively, XPS measurement provided an understanding of the mechanism, suggesting hydrogen bonding and dipole-dipole interactions as the main interactions between SO2 molecules and SBA-15_6.1APTES. DFT calculations were performed to confirm these interactions. Furthermore, this study highlights the application of SBA-15 materials with different amino modifications for SO2 treatment and provides insight into the interaction mechanism using experimental techniques.

SO2 capture and detection with carbon microfibers (CMFs) synthesised from polyacrylonitrile.

SO2 emissions not only affect local air quality but can also contribute to other environmental issues. Developing low-cost and robust adsorbents with high uptake and selectivity is needed to reduce SO2 emissions. Here, we show the SO2 adsorption-desorption capacity of carbon microfibers (CMFs) at 298 K. CMFs showed a reversible SO2 uptake capacity (5 mmol g-1), cyclability over ten adsorption cycles with fast kinetics and good selectivity towards SO2/CO2 at low-pressure values. Additionally, CMFs' photoluminescence response to SO2 and CO2 was evaluated.

Computational tools to study non-covalent interactions and confinement effects in chemical systems.

Confinement is a very common phenomenon in chemistry, for example, when molecules are located inside cavities. In these conditions, the electronic structure of atoms and molecules is modified. These changes could be mapped through the interaction with other molecules since non-covalent interactions between molecules are also influenced by confinement. In this work we address both topics, non-covalent interactions, and confined systems, using quantum chemistry tools with new software, emphasizing the importance of analyzing both fields simultaneously.

Copper(II)-MOFs for bio-applications.

The recent development and implementation of copper-based metal-organic frameworks in biological applications are reviewed. The advantages of the presence of copper in MOFs for relevant applications such as drug delivery, cancer treatment, sensing, and antimicrobial are highlighted. Advanced composites such as MOF-polymers are playing critical roles in developing materials for specific applications.

MFM-300(Sc): a chemically stable Sc(III)-based MOF material for multiple applications.

Developing robust multifunctional metal-organic frameworks (MOFs) is the key to advancing the further deployment of MOFs into relevant applications. Since the first report of MFM-300(Sc) (MFM = Manchester Framework Material, formerly known as NOTT-400), the development of applications of this robust microporous MOF has only grown. In this review, a summary of the applications of MFM-300(Sc), as well as some emerging advanced applications, have been discussed. The adsorption properties of MFM-300(Sc) are presented systematically. Particularly, this contribution is focused on acid and corrosive gas adsorption. In addition, recent applications for catalysis based on the outstanding hemilabile Sc-O bond character are highlighted. Finally, some new research areas are introduced, such as host-guest chemistry and biomedical applications. This highlight aims to showcase the recent advances and the potential for developing new applications of this promising material.

MOF-based catalysts: insights into the chemical transformation of greenhouse and toxic gases.

Metal-organic framework (MOF)-based catalysts are outstanding alternative materials for the chemical transformation of greenhouse and toxic gases into high-add-value products. MOF catalysts exhibit remarkable properties to host different active sites. The combination of catalytic properties of MOFs is mentioned in order to understand their application. Furthermore, the main catalytic reactions, which involve the chemical transformation of CH4, CO2, NOx, fluorinated gases, O3, CO, VOCs, and H2S, are highlighted. The main active centers and reaction conditions for these reactions are presented and discussed to understand the reaction mechanisms. Interestingly, implementing MOF materials as catalysts for toxic gas-phase reactions is a great opportunity to provide new alternatives to enhance the air quality of our planet.

Low-Valent Metals in Metal-Organic Frameworks Via Post-Synthetic Modification.

Metal-organic frameworks (MOFs) provide uniquely tunable, periodic platforms for site-isolation of reactive low-valent metal complexes of relevance in modern catalysis, adsorptive applications, and fundamental structural studies. Strategies for integrating such species in MOFs include post-synthetic metalation, encapsulation and direct synthesis using low-valent organometallic complexes as building blocks. These approaches have each proven effective in enhancing catalytic activity, modulating product distributions (i.e., by improving catalytic selectivity), and providing valuable mechanistic insights. In this minireview, we explore these different strategies, as applied to isolate low-valent species within MOFs, with a particular focus on examples that leverage the unique crystallinity, permanent porosity and chemical mutability of MOFs to achieve deep structural insights that lead to new paradigms in the field of hybrid catalysis.

SU-101: a Bi(III)-based metal-organic framework as an efficient heterogeneous catalyst for the CO2 cycloaddition reaction.

A non-porous version of SU-101 (herein n-SU-101) was evaluated for the CO2 cycloaddition reaction. The findings revealed that open metal sites (Bi3+) are necessary for the reaction. n-SU-101 displays a high styrene oxide conversion of 96.6% under mild conditions (3 bar and 80 °C). The catalytic activity of n-SU-101 demonstrated its potential application for the cycloaddition of CO2 using styrene oxide.

Detection of SO2 using a chemically stable Ni(II)-MOF.

The MOF-type Ni2(dobpdc) shows a high chemical stability towards SO2, high capacity for SO2 capture at low pressure (4.3 mmol g-1 at 298 K and up to 0.05 bar), and exceptional cycling performance. Fluorescence experiments demonstrated the SO2 detection properties of Ni2(dobpdc) with a remarkable SO2 detection selectivity. Finally, time-resolved photoluminescence experiments provided a plausible mechanism of SO2 detection by this Ni(II)-based MOF material.

Modulated self-assembly of three flexible Cr(III) PCPs for SO2 adsorption and detection.

Modulated self-assembly protocols are used to develop facile, HF-free syntheses of the archetypal flexible PCP, MIL-53(Cr), and novel isoreticular analogues MIL-53(Cr)-Br and MIL-53(Cr)-NO2. All three PCPs show good SO2 uptake (298 K, 1 bar) and high chemical stabilities against dry and wet SO2. Solid-state photoluminescence spectroscopy indicates all three PCPs exhibit turn-off sensing of SO2, in particular MIL-53(Cr)-Br, which shows a 2.7-fold decrease in emission on exposure to SO2 at room temperature, indicating potential sensing applications.

Encapsulation of dopamine within SU-101: insights by computational chemistry.

Encapsulating and protecting dopamine from oxidation is a difficult challenge. We propose to use SU-101 BioMOF as a dopamine host, where we study different adsorption scenarios by a robust computational approach. Our results show that dopamine encapsulation is feasible with the formation of non-covalent interactions within the SU-101 pores. These computational results have been corroborated experimentally.

Gas-phase organometallic catalysis in MFM-300(Sc) provided by switchable dynamic metal sites.

MFM-300(Sc) was explored as a catalyst for the gas-phase hydrogenation of acetone. The catalysis results support the presence of non-permanent open Sc(III) sites within the structure due to the requirement of Lewis acid sites for the reaction to proceed. The open Sc(III) sites are generated in situ due to the presence of hemilabile Sc-O bonds. MFM-300(Sc) showed high mechanical and chemical stability, and the crystalline structure was maintained after the catalytic reaction. The catalytic activity of the material was quantified by performing a gas-phase reaction using a continuous flow reactor. The acetone conversion in MFM-300(Sc) was estimated to be 27.7% with no loss of activity after catalytic cycles.

SO2 capture enhancement due to confined methanol within MIL-53(Al)-TDC.

The SO2 capture performance of MIL-53(Al)-TDC was optimised by confining a small amount of MeOH within its pores (MeOH@MIL-53(Al)-TDC). In comparison with fully activated MIL-53(Al)-TDC, MeOH@MIL-53(Al)-TDC shows a 39% higher SO2 capture capacity. Monte Carlo simulations revealed that such an enhancement is associated with an increase in the degree of confinement via the SO2 molecules resulting from the formation of a lump (MeOH molecules) in the vicinity of the µ-OH groups.

SO2 capture and detection using a Cu(II)-metal-organic polyhedron.

The SO2 adsorption-desorption capacity at room temperature and 1 bar of the metal-organic polyhedron MOP-CDC was investigated. In addition, the qualitative solid-state absorption-emission properties of this material (before and after SO2 exposure) were measured and tested, and it demonstrated remarkable capability for SO2 detection. Our results represent the first example of fluorimetric SO2 detection in a MOP.

Linezolid@MOF-74 as a host-guest system with antimicrobial activity.

Linezolid (LNZ) is a new-generation synthetic molecule for the antibacterial treatment of severe infections, particularly in infective cases where the bacterial resistance to first-choice drugs is caused by Gram-positive pathogens. In this context, since 2009, some strains resistant to LNZ in patients with long-term treatments have been reported. Therefore, there is a need to use not only new drug molecules with antibacterial activities in the dosage form but also a different approach to pharmacotherapeutic strategies for skin infections, which lead to a reduction in the concentration of biocides. This work explores LNZ hosted at two isostructural MOFs, MOF-74(Zn) and MOF-74(Cu), as promising antimicrobial systems for gradual biocide release within 6 h. These systems reach a lower minimum inhibitory concentration (MIC) in comparison to free LNZ. Even a decreased MIC value is also observed, which is an encouraging result regarding the efficiency of the systems to control concentration-dependent antimicrobial resistance.

Gold nanoparticles: current and upcoming biomedical applications in sensing, drug, and gene delivery.

Gold nanoparticles (AuNPs) present unique physicochemical characteristics, low cytotoxicity, chemical stability, size/morphology tunability, surface functionalization capability, and optical properties which can be exploited for detection applications (colorimetry, surface-enhanced Raman scattering, and photoluminescence). The current challenge for AuNPs is incorporating these properties in developing more sensible and selective sensing methods and multifunctional platforms capable of controlled and precise drug or gene delivery. This review briefly highlights the recent progress of AuNPs in biomedicine as bio-sensors and targeted nano vehicles.

Coloured hybrid materials: exploiting an emergent surface property of fluorinated Al2O3 containing anthocyanins and betacyanins.

Two fluorinated γ-Al2O3 series were synthesized by a sol-gel method with two solvents (2-propanol and 2-butanol), two aluminium sources (ATB and ATP) and one fluorine source (Na3AlF6). The resulting inorganic matrixes were evaluated to characterize aluminium and fluorine species ([AlO45-], [AlO57-], [AlO69-], [AlF4-], [AlF52-] and [AlF63-]) by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), 27Al magic angle spinning nuclear magnetic resonance (27Al MAS-NMR) and infrared spectroscopy (IR-ATR). BET and BJH analyses using the nitrogen isotherms of these materials allowed identifying a clear trend in some textural parameters such as specific surface area and fluorine content. These results were confirmed by scanning electron microscopy (SEM). Chemical affinity and acid surface properties were evidenced with colour shifts in two groups of hybrid pigments, prepared with natural anthocyanins (Brassica oleracea) and betacyanins (Bougainvillea glabra).

Sc(III)-Based metal-organic frameworks.

Scandium(III) ions can form robust metal-organic frameworks (MOFs) with relative ease of synthesis. However, their use in MOF construction remains scarce compared to the vast collection of MOFs using other ions. This highlight features the chronological development of Sc(III)-MOFs, which attest to the ability of Sc(III) ions to afford materials that combine exceptional stability with catalytic or photo-physical attributes.

SO2 Capture by Two Aluminum-Based MOFs: Rigid-like MIL-53(Al)-TDC versus Breathing MIL-53(Al)-BDC.

Metal-organic frameworks MIL-53(Al)-TDC and MIL-53(Al)-BDC were explored in the SO2 adsorption process. MIL-53(Al)-TDC was shown to behave as a rigid-like material upon SO2 adsorption. On the other hand, MIL-53(Al)-BDC exhibits guest-induced flexibility of the framework with the presence of multiple steps in the SO2 adsorption isotherm that was related through molecular simulations to the existence of three different pore opening phases narrow pore, intermediate pore, and large pore. Both materials proved to be exceptional candidates for SO2 capture, even under wet conditions, with excellent SO2 adsorption, good cycling, chemical stability, and easy regeneration. Further, we propose MIL-53(Al)-TDC and MIL-53(A)-BDC of potential interest for SO2 sensing and SO2 storage/transportation, respectively.