A series of four novel alkaline earth metal-organic frameworks constructed of Ca(ii), Sr(ii), Ba(ii) ions and tetrahedral MTB linker: structural diversity, stability study and low/high-pressure gas adsorption properties

Cellulose-Amine Porous Materials: The Effect of Activation Method on Structure, Textural Properties, CO2 Capture, and Recyclability

CO2 capture via physical adsorption on activated porous carbons represents a promising solution towards effective carbon emission mitigation. Additionally, production costs can be further decreased by utilising biomass as the main precursor and applying energy-efficient activation. In this work, we developed novel cellulose-based activated carbons modified with amines (diethylenetriamine (DETA), 1,2-bis(3-aminopropylamino)ethane (BAPE), and melamine (MELA)) with different numbers of nitrogen atoms as in situ N-doping precursors. We investigated the effect of hydrothermal and thermal activation on the development of their physicochemical properties, which significantly influence the resulting CO2 adsorption capacity. This process entailed an initial hydrothermal activation of biomass precursor and amines at 240 °C, resulting in C+DETA, C+BAPE and C+MELA materials. Thermal samples (C+DETA (P), C+BAPE (P), and C+MELA (P)) were synthesised from hydrothermal materials by subsequent KOH chemical activation and pyrolysis in an inert argon atmosphere. Their chemical and structural properties were characterised using elemental analysis (CHN), infrared spectroscopy (IR), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). The calculated specific surface areas (SBET) for thermal products showed higher values (998 m2 g-1 for C+DETA (P), 1076 m2 g-1 for C+BAPE (P), and 1348 m2 g-1 for C+MELA (P)) compared to the hydrothermal products (769 m2 g-1 for C+DETA, 833 m2 g-1 for C+BAPE, and 1079 m2 g-1 for C+MELA). Carbon dioxide adsorption as measured by volumetric and gravimetric methods at 0 and 25 °C, respectively, showed the opposite trend, which can be attributed to the reduced content of primary adsorption sites in the form of amine groups in thermal products. N2 and CO2 adsorption measurements were carried out on hydrothermal (C) and pyrolysed cellulose (C (P)), which showed a several-fold reduction in adsorption properties compared to amine-modified materials. The recyclability of C+MELA, which showed the highest CO2 adsorption capacity (7.34 mmol g-1), was studied using argon purging and thermal regeneration over five adsorption/desorption cycles.

Calcium l-Malate and d-Tartarate Frameworks as Adjuvants for the Sustainable Delivery of a Fungicide

Agrichemical adjuvants that combine a highly selective, efficient, and active mode of operation are critically needed to realize a more sustainable approach to their usage. Herein, we report the synthesis and full characterization of two new metal-organic frameworks (MOFs), termed UPMOF-1 and UPMOF-2, that were constructed from eco-friendly Ca2+ ions and naturally occurring, low-molecular weight plant acids, l-malic and d-tartaric acid, respectively. Upon structural elucidation of both MOFs, a widely used fungicide, hexaconazole (Hex), was loaded on the structures, reaching binding affinities of -5.0 and -3.5 kcal mol-1 and loading capacities of 63% and 62% for Hex@UPMOF-1 and Hex@UPMOF-2, respectively, as a result of the formation of stable host-guest interactions. Given the framework chemistry of the MOFs and their predisposition to disassembly under relevant agricultural conditions, the sustained release kinetics were determined to show nearly quantitative release (98% and 95% for Hex@UPMOF-1 and Hex@UPMOF-2, respectively) after >500 h, a release profile drastically different than the control (>80% release in 24 h), from which the high efficiency of these new systems was established. To confirm their high selectivity and activity, in vitro and in vivo studies were performed to illustrate the abilities of Hex@UPMOF-1 and Hex@UPMOF-2 to combat the known aggressive pathogen Ganoderma boninense that causes basal stem rot disease in oil palm. Accordingly, at an extremely low concentration of 0.05 μg mL-1, both Hex@UPMOF-1 and Hex@UPMOF-2 were demonstrated to completely inhibit (100%) G. boninense growth, and during a 26 week in vivo nursery trial, the progression of basal stem rot infection was completely halted upon treatment with Hex@UPMOF-1 and Hex@UPMOF-2 and seedling growth was accelerated given the additional nutrients supplied via the disassembly of the MOFs. This study represents a significant step forward in the design of adjuvants to support the environmentally responsible use of agrichemical crop protection.

Strategies for enhanced bioavailability of oxime reactivators in the central nervous system

Oxime reactivators of acetylcholinesterase are commonly used to treat highly toxic organophosphate poisoning. They are effective nucleophiles that can restore the catalytic activity of acetylcholinesterase; however, their main limitation is the difficulty in crossing the blood-brain barrier (BBB) because of their strongly hydrophilic nature. Various approaches to overcome this limitation and enhance the bioavailability of oxime reactivators in the CNS have been evaluated; these include structural modifications, conjugation with molecules that have transporters in the BBB, bypassing the BBB through intranasal delivery, and inhibition of BBB efflux transporters. A promising approach is the use of nanoparticles (NPs) as the delivery systems. Studies using mesoporous silica nanomaterials, poly (L-lysine)-graft-poly(ethylene oxide) NPs, metallic organic frameworks, poly(lactic-co-glycolic acid) NPs, human serum albumin NPs, liposomes, solid lipid NPs, and cucurbiturils, have shown promising results. Some NPs are considered as nanoreactors for organophosphate detoxification; these combine bioscavengers with encapsulated oximes. This study provides an overview and critical discussion of the strategies used to enhance the bioavailability of oxime reactivators in the central nervous system.

A highly stable terbium(III) metal-organic framework MOF-76(Tb) for hydrogen storage and humidity sensing

The present study described the synthesis and characterization of MOF-76(Tb) for hydrogen storage and humidity sensing applications. The structure and morphology of as-synthesized material were studied using powder X-ray diffraction, scanning, and transmission electron microscopy. The crystal structure of MOF-76(Tb) consists of terbium(III) and benzene-1,3,5-tricarboxylate(-III) ions, one coordinated aqua ligand and one crystallization N,N´-dimethylformamide molecule. The polymeric framework of MOF-76(Tb) contains 1D sinusoidally shaped channels with sizes of 6.6 × 6.6 Å propagating along c crystallographic axis. The thermogravimetric analysis of the prepared material exhibited thermal stability up to 600 °C. At 77 K and pressure up to 20 bar; 0.6 wt.% hydrogen storage capacity for MOF-76(Tb) was observed. Finally, the humidity sensing measurements (water adsorption experiments) were performed, and the results indicate that MOF-76(Tb) is not a suitable material for moisture sensing applications.

Nanocapsules of unprecedented internal volume seamed by calcium ions

The inception of an unprecedented class of voluminous Platonic solids displaying hierarchical geometry based on pyrogallol[4]arene moieties seamed by divalent calcium ion is described. Single-crystal X-ray structural determination has established the highly conserved geometry of two original Ca2+-seamed nanocapsules to be essentially cubic in shape with C-ethylpyrogallol[4]arene units located along the twelve edges of the cube which are then bridged by metallic polyatomic cations ([Ca4Cl]7+ or [Ca(HCO2)Na4]5+) at the six cube faces. The accessible volume of the nanocapsules is ca. 3500 Å3 and 2500 Å3 and is completely isolated from the exterior of the capsules. These remarkable nanocapsule discoveries cast a spotlight on a marginalized area of synthetic materials chemistry and encourage future exploration of diversiform supramolecular assemblies, networks, and capsules built on calcium, with clear benefits deriving from the intrinsic biocompatibility of calcium. Finally, a proof-of-concept is demonstrated for fluorescent reporter encapsulation and sustained release from the calcium-seamed nanocapsules, suggesting their potential as delivery vehicles for drugs, nutrients, preservatives, or antioxidants.

Sr(II) and Ba(II) Alkaline Earth Metal-Organic Frameworks (AE-MOFs) for Selective Gas Adsorption, Energy Storage, and Environmental Application

Two new alkaline earth metal-organic frameworks (AE-MOFs) containing Sr(II) (UPJS-15) or Ba(II) (UPJS-16) cations and extended tetrahedral linker (MTA) were synthesized and characterized in detail (UPJS stands for University of Pavol Jozef Safarik). Single-crystal X-ray analysis (SC-XRD) revealed that the materials are isostructural and, in their frameworks, one-dimensional channels are present with the size of ~11 × 10 Ų. The activation process of the compounds was studied by the combination of in situ heating infrared spectroscopy (IR), thermal analysis (TA) and in situ high-energy powder X-ray diffraction (HE-PXRD), which confirmed the stability of compounds after desolvation. The prepared compounds were investigated as adsorbents of different gases (Ar, N₂, CO₂, and H₂). Nitrogen and argon adsorption measurements showed that UPJS-15 has S_BET area of 1321 m² g^-1 (Ar) / 1250 m² g^-1 (N₂), and UPJS-16 does not adsorb mentioned gases. From the environmental application, the materials were studied as CO₂ adsorbents, and both compounds adsorb CO₂ with a maximum capacity of 22.4 wt.% @ 0 °C; 14.7 wt.% @ 20 °C and 101 kPa for UPJS-15 and 11.5 wt.% @ 0°C; 8.4 wt.% @ 20 °C and 101 kPa for UPJS-16. According to IAST calculations, UPJS-16 shows high selectivity (50 for CO₂/N₂ 10:90 mixture and 455 for CO₂/N₂ 50:50 mixture) and can be applied as CO₂ adsorbent from the atmosphere even at low pressures. The increased affinity of materials for CO₂ was also studied by DFT modelling, which revealed that the primary adsorption sites are coordinatively unsaturated sites on metal ions, azo bonds, and phenyl rings within the MTA linker. Regarding energy storage, the materials were studied as hydrogen adsorbents, but the materials showed low H₂ adsorption properties: 0.19 wt.% for UPJS-15 and 0.04 wt.% for UPJS-16 @ -196 °C and 101 kPa. The enhanced CO₂/H₂ selectivity could be used to scavenge carbon dioxide from hydrogen in WGS and DSR reactions. The second method of applying samples in the area of energy storage was the use of UPJS-15 as an additive in a lithium-sulfur battery. Cyclic performance at a cycling rate of 0.2 C showed an initial discharge capacity of 337 mAh g^-1, which decreased smoothly to 235 mAh g^-1 after 100 charge/discharge cycles.

Carbon dioxide and hydrogen adsorption study on surface-modified HKUST-1 with diamine/triamine

The present article intended to study the influence of post-synthetic modification with ethylenediamine (en, diamine) and diethylenetriamine (deta, triamine) within the coordinatively unsaturated sites (CUSs) of HKUST-1 on carbon dioxide and hydrogen storage. The as-sythesized adsorbent was solvent-exchanged and subsequently post-synthetically modified with di-/triamines as sources of amine-based sorption sites due to the increased CO₂ storage capacity. It is known that carbon dioxide molecules have a high affinity for amine groups, and moreover, the volume of amine molecules itself reduces the free pore volume in HKUST-1, which is the driving force for increasing the hydrogen storage capacity. Different concentrations of amines were used for modification of HKUST-1, through which materials with different molar ratios of HKUST-1 to amine: 1:0.05; 1:0.1; 1:0.25; 1:0.5; 1:0.75; 1:1; 1:1.5 were synthesized. Adsorption measurements of carbon dioxide at 0 °C up to 1 bar have shown that the compounds can adsorb large amounts of carbon dioxide. In general, deta-modified samples showed higher adsorbed amounts of CO₂ compared to en-modified materials, which can be explained by the higher number of amine groups within the deta molecule. With an increasing molar ratio of amines, there was a decrease in wt.% CO₂. The maximum storage capacity of CO₂ was 22.3 wt.% for HKUST-1: en/1:0.1 and 33.1 wt.% for HKUST-1: deta/1:0.05 at 0 °C and 1 bar. Hydrogen adsorption measurements showed the same trend as carbon dioxide, with the maximum H₂ adsorbed amounts being 1.82 wt.% for HKUST-1: en/1:0.1 and 2.28 wt.% for HKUST-1: deta/1:0.05 at − 196 °C and 1 bar.

Gd(III) metal-organic framework as an effective humidity sensor and its hydrogen adsorption properties

Metal-organic frameworks (MOFs) represent a class of nanoporous materials built up by metal ions and organic linkers with several interesting potential applications. The present study described the synthesis and characterization of Gd(III)-based MOF with the chemical composition [Gd(BTC)(H₂O)]·DMF (BTC - trimesate, DMF = N,N'-dimethylformamide), known as MOF-76(Gd) for hydrogen adsorption/desorption capacity and humidity sensing applications. The structure and morphology of as-synthesized material were studied using powder X-ray diffraction, scanning and transmission electron microscopy. The crystal structure of MOF-76(Gd) consists of gadolinium (III) and benzene-1,3,5-tricarboxylate ions, one coordinated aqua ligand and one crystallization DMF molecule. The polymeric framework of MOF-76(Gd) contains 1D sinusoidally shaped channels with sizes of 6.7 × 6.7 Å propagating along c crystallographic axis. The thermogravimetric analysis, heating infrared spectroscopy and in-situ heating powder X-ray diffraction experiments of the prepared framework exhibited thermal stability up to 550 °C. Nitrogen adsorption/desorption measurement at -196 °C showed a BET surface area of 605 m² g^-1 and pore volume of 0.24 cm³ g^-1. The maximal hydrogen storage capacity of MOF-76(Gd) was 1.66 wt % and 1.34 wt % -196 °C and -186 °C and pressure up to 1 bar, respectively. Finally, the humidity sensing measurements (water adsorption experiments) were performed, and the results indicate that MOF-76(Gd) is a suitable material for moisture sensing application with a fast response (11 s) and recovery time (2 s) in the relative humidity range of 11-98%.

Nanomaterials and metal-organic frameworks for biosensing applications of mutations of the emerging viruses

The world today lives in a state of terrible fear due to the mutation of the emerging COVID-19. With the continuation of this pandemic, there is an urgent need for fast, accurate testing devices to detect the emerging SARS-CoV-2 pandemic in terms of biosensors and point-of-care testing. Besides, the urgent development in personal defense tools, anti-viral surfaces and wearables, and smartphones open the door for simplifying the self-diagnosis process everywhere. This review introduces a quick COVID-19 overview: definition, transmission, pathophysiology, the identification and diagnosis, mutation and transformation, and the global situation. It also focuses on an overview of the rapidly advanced technologies based on nanomaterials and MOFs for biosensing, diagnosing, and viral control of the SARS-CoV-2 pandemic. Finally, highlight the latest technologies, applications, existing achievements, and preventive diagnostic strategies to control this epidemic and combat the emerging coronavirus. This humble effort aims to provide a helpful survey that can be used to develop a creative solution and to lay down the future vision of diagnosis against COVID-19.

Outstanding fluoride removal from aqueous solution by a La-based adsorbent†

A La-based adsorbent was prepared with La(NO₃)₃·6H₂O, 2-methylimidazole and DMF via amide-hydrolysis and used for fluoride decontamination from aqueous water. The obtained adsorbent was lanthanum methanoate (La(COOH)₃). The effects of pH value, initial F⁻ concentration and interfering ions on defluoridation properties of as-prepared La(COOH)₃ were assessed through batch adsorption tests. The adsorption kinetics, isotherm models and thermodynamics were employed to verify the order, nature and feasibility of La(COOH)₃ towards fluoride removal. The results imply that La(COOH)₃ is preferable for defluoridation over a wide pH range of 2 to 9 without interference. Simultaneously, the defluoridation process of La(HCOO)₃ accords to the pseudo-second order model and Langmuir isotherm, revealing chemical adsorption is the main control step. The maximum fluoride capture capacities of La(COOH)₃ at 30, 40 and 50 °C are 245.02, 260.40 and 268.99 mg g⁻¹, respectively. The mechanism for defluoridation by La(COOH)₃ was revealed by PXRD and XPS. To summarize, the as-synthesized La based adsorbent could serve as a promising adsorbent for defluoridation from complex fluoride-rich water.

A La-based adsorbent was prepared with La(NO₃)₃·6H₂O, 2-methylimidazole and DMF via amide-hydrolysis and used for fluoride decontamination from aqueous water.

Post-synthetically modified metal–porphyrin framework GaTCPP for carbon dioxide adsorption and energy storage in Li–S batteries

Metal–porphyrin framework GaTCPP was used for carbon dioxide adsorption and as a host for preparation of a Li–S battery cathode material.

Anticancer Activity of New Na(I) Complex on Retinoblastoma Cells via Inhibiting PI3K/AKT/mTOR Pathway

Here, through applying 2,6-bis(4'-carboxyl-phenyl)pyridine (H2L), a rigid ligand featuring both carboxylic acid and pyridine groups, a new coordination polymer containing Na(I) has been generated with the reaction between H2L ligand and NaNO3 in a water and DMF mixed solvent, and its chemical composition is [Na2L]n. Furthermore, the antiproliferative activity of Na(I) complex against the HXO-Rb44 retinoblastoma cells was detected with CCK-8 assay. Hoechst staining along with Annexin V-FITC/PI revealed that Na(I) complex induces the HXO-Rb44 retinoblastoma cells apoptosis. Flow cytometry analysis of reactive oxygen species (ROS) showed that Na(I) complex significantly increases the level of intracellular ROS. Importantly, western blot analysis revealed that Na(I) complex might induce apoptosis through inactivation of PI3K/AKT/mTOR pathway.

Construction of Two Stable Co(II)-Based Hydrogen-Bonded Organic Frameworks as a Luminescent Probe for Recognition of Fe3+ and Cr2O72- in H2O

A pair of cobalt(II)-based hydrogen-bonded organic frameworks (HOFs), [Co(pca)2(bmimb)]n (1) and [Co2(pca)4(bimb)2] (2), where Hpca = p-chlorobenzoic acid, bmimb = 1,3-bis((2-methylimidazol-1-yl)methyl)benzene, and bimb = 1,4-bis(imidazol-1-ylmethyl)benzene were hydrothermally synthesized and characterized through infrared spectroscopy (IR), elemental and thermal analysis (EA), power X-ray diffraction (PXRD), and single-crystal X-ray diffraction (SCXRD) analyses. X-ray diffraction structural analysis revealed that 1 has a one-dimensional (1D) infinite chain network through the deprotonated pca- monodentate chelation and with a μ2-bmimb bridge Co(II) atom, and 2 is a binuclear Co(II) complex construction with a pair of symmetry-related pca- and bimb ligands. For both 1 and 2, each cobalt atom has four coordinated twisted tetrahedral configurations with a N2O2 donor set. Then, 1 and 2 are further extended into three-dimensional (3D) or two-dimensional (2D) hydrogen-bonded organic frameworks through C-H···Cl interactions. Topologically, HOFs 1 and 2 can be simplified as a 4-connected qtz topology with a Schläfli symbol {64·82} and a 4-connected sql topology with a Schläfli symbol {44·62}, respectively. The fluorescent sensing application of 1 was investigated; 1 exhibits high sensitivity recognition for Fe3+ (Ksv: 10970 M-1 and detection limit: 19 μM) and Cr2O72- (Ksv: 12960 M-1 and detection limit: 20 μM). This work provides a feasible detection platform of HOFs for highly sensitive discrimination of Fe3+ and Cr2O72- in aqueous media.

Novel Lanthanide(III) Porphyrin-Based Metal-Organic Frameworks: Structure, Gas Adsorption, and Magnetic Properties

The present work focuses on the hydrothermal synthesis and properties of porous coordination polymers of metal-porphyrin framework (MPF) type, namely, {[Pr4(H2TPPS)3]·11H2O} n (UPJS-10), {[Eu/Sm(H2TPPS)]·H3O+·16H2O} n (UPJS-11), and {[Ce4(H2TPPS)3]·11H2O} n (UPJS-12) (H2TPPS = 4,4',4″,4‴-(porphyrin-5,10,15,20-tetrayl)tetrakisbenzenesulfonate(4-)). The compounds were characterized using several analytical techniques: infrared spectroscopy, thermogravimetric measurements, elemental analysis, gas adsorption measurements, and single-crystal structure analysis (SXRD). The results of SXRD revealed a three-dimensional open porous framework containing crossing cavities propagating along all crystallographic axes. Coordination of H2TPPS4- ligands with Ln(III) ions leads to the formation of 1D polymeric chains propagating along the c crystallographic axis. Argon sorption measurements at -186 °C show that the activated MPFs have apparent BET surface areas of 260 m2 g-1 (UPJS-10) and 230 m2 g-1 (UPJS-12). Carbon dioxide adsorption isotherms at 0 °C show adsorption capacities up to 1 bar of 9.8 wt % for UPJS-10 and 8.6 wt % for UPJS-12. At a temperature of 20 °C, the respective CO2 adsorption capacities decreased to 6.95 and 5.99 wt %, respectively. The magnetic properties of UPJS-10 are characterized by the presence of a close-lying nonmagnetic ground singlet and excited doublet states in the electronic spectrum of Pr(III) ions. A much larger energy difference was suggested between the two lowest Kramers doublets of Ce(III) ions in UPJS-12. Finally, the analysis of X-band EPR spectra revealed the presence of radical spins, which were tentatively assigned to be originating from the porphyrin ligands.

Zinc(ii) and cadmium(ii) amorphous metal-organic frameworks (aMOFs): study of activation process and high-pressure adsorption of greenhouse gases

Two novel amorphous metal-organic frameworks (aMOFs) with chemical composition {[Zn₂(MTA)]·4H₂O·3DMF} _n (UPJS-13) and {[Cd₂(MTA)]·5H₂O·4DMF} _n (UPJS-14) built from Zn(ii) and Cd(ii) ions and extended tetrahedral tetraazo-tetracarboxylic acid (H₄MTA) as a linker were prepared and characterised. Nitrogen adsorption measurements were performed on as-synthesized (AS), ethanol exchanged (EX) and freeze-dried (FD) materials at different activation temperatures of 60, 80, 100, 120, 150 and 200 °C to obtain the best textural properties. The largest surface areas of 830 m² g^-1 for UPJS-13 (FD) and 1057 m² g^-1 for UPJS-14 (FD) were calculated from the nitrogen adsorption isotherms for freeze-dried materials activated at mild activation temperature (80 °C). Subsequently, the prepared compounds were tested as adsorbents of greenhouse gases, carbon dioxide and methane, measured at high pressures. The maximal adsorption capacities were 30.01 wt% CO₂ and 4.84 wt% CH₄ for UPJS-13 (FD) and 24.56 wt% CO₂ and 6.38 wt% CH₄ for UPJS-14 (FD) at 20 bar and 30 °C.

Alkaline earth-organic frameworks with amino derivatives of 2,6-naphthalene dicarboxylates: structural studies and fluorescence properties

Alkaline earth metal ion organic frameworks (AEMOFs) represent a relatively underexplored subcategory of metal-organic frameworks (MOFs). In this contribution, we present the synthesis and structural study of the new MOFs 1-8 based on the alkaline earth ions Mg2+, Ca2+, Sr2+ and Ba2+ and the amino substituted bridging ligands 4-aminonaphthalene-2,6-dicarboxylate (ANDC2-) and 4,8-diaminonaphthalene-2,6-dicarboxylate (DANDC2-). Compounds 1, 5, 6, 7 and 8 constitute rare examples of three-dimensional MOFs which feature square planar M4 secondary building units (SBUs) surrounded by eight bridging ditopic ligands. The underlying topology of MOFs 1, 5, 7 and 8 conforms to the 4-c pcb net which can be simplified to the 8-c bcu net, while 6 adopts the 4-c lta net which simplifies to the 8-c reo net. To the best of our knowledge these are the first examples of MOFs of their structural types formed by linear dicarboxylates instead of trigonal tricarboxylates or tetrahedral tetracarboxylates. Compounds 2, 3 and 4 also feature three dimensional networks with linear rod-shaped SBUs with the Ba2+ MOF 3 displaying an sra rod-net and MOFs 2 and 4 showing very complex rod-nets with so far unique topologies. Fluorescence studies revealed that the free ligands exhibit strong blue-green emission displaying considerable positive solvatochromism thereby pointing towards charge transfer excited states involving the shift of electron density from the amino groups to the aromatic core. Correspondingly, the MOFs display ligand based fluorescence with small differences in emission maxima possibly attributable to the difference in the charge density of the metal ions combined with the different environments around ligands in the crystal structures.