Cooperative Effect of Unsheltered Amide Groups on CO2 Adsorption Inside Open-Ended Channels of a Zinc(II)–Organic Framework

Electro-oxidation sensing of sumatriptan in aqueous solutions and human blood serum by Zn(II)-MOF modified electrochemical delaminated pencil graphite electrode

An electrochemical sensory platform is presented for determination of sumatriptan (SUM) in aqueous solutions and human blood serum. A pencil graphite electrode (PGE) was electrochemically delaminated by cyclic voltammetry technique, and then further modified using nanoparticles of a zinc-based metal-organic framework (Zn(II)-MOF). The fabricated Zn(II)-MOF/EDPGE electrode was utilized for sensitive electrochemical detection of SUM via an electro-oxidation reaction. The Zn(II)-MOF was hydrothermally synthesized and characterized by various techniques. The electrochemical delamination of PGE results in a porous substrate, facilitating the effective immobilization of the modifier. The designed sensor benefits from both enhanced surface area and an accelerated electron transfer rate, as evidenced by the chronocoulogram and Nyquist plots. Under optimized conditions, the developed sensor exhibited a linear response for 0.99-9.52 µM SUM solutions. A short response time of 5 s was observed for the fabricated sensor and the detection limit was found to be 0.29 μM. Selectivity of Zn(II)-MOF/EDPGE towards SUM was evaluated by examining the interference effect of codeine, epinephrine, acetaminophen, ascorbic acid, and uric acid, which are commonly found in biological samples. The developed sensor shows excellent performance with recovery values falling within the range of 96.6 to 111% for the analysis of SUM in human blood serum samples.

Multi-responsive luminescent sensitivities of two pillared-layer frameworks towards nitroaromatics, Cr2O72-, MnO4- and PO43- anions

Combining Zn(II) with two dicarboxylic acids of different length and functional groups results in the 2D metal-carboxylate layer of different size and shape, which are further connected by the same bis-pyridyl-bis-amide pillar to afford two 4-fold and 3-fold interpenetrating pillared-layer networks (1 and 2). Luminescent properties of 1 and 2 have been systematically investigated and demonstrated multi-responsive luminescent sensitivities. 1 can be used for highly sensitive detection of nitroaromatics. In particular, 2 can be used turn-off sensing towards Cr₂O₇^2- and MnO₄^- anions as well as turn-on sensing towards PO₄^3- anion in aqueous solution with high sensitivity and remarkable recyclability. The sensing mechanism is also discussed.

Eight-Fold Interpenetrating Diamondoid Coordination Polymers for Sensing Volatile Organic Compounds and Metal Ions

Reactions of divalent metal salts with 4,4-oxybis(N-(pyridine-4-yl)-benzamide), L, and naphthalene-1,4-dicarboxylic acid (1,4-H₂NDC) in various solvents gave [Zn(L)(1,4-NDC)·H₂O]_n, 1, [Cd(L)(1,4-NDC)(H₂O)·MeOH]_n, 2, and [Co(L)(1,4-NDC)(H₂O)_0.5·MeOH]_n, 3, which have been structurally characterized. Complexes 1–3 show eight-fold interpenetrating frameworks with the dia topology, which exhibit porosities substantiated by CO₂ adsorption, whereas 1 and 2 manifest stability in aqueous environments and show high selectivity toward sensing of mesitylene molecules and Fe³⁺ ions with low detection limits and good reusability up to five cycles.

Covalent Triazine Frameworks Based on the First Pseudo-Octahedral Hexanitrile Monomer via Nitrile Trimerization: Synthesis, Porosity, and CO2 Gas Sorption Properties

Herein, we report the first synthesis of covalent triazine-based frameworks (CTFs) based on a hexanitrile monomer, namely the novel pseudo-octahedral hexanitrile 1,4-bis(tris(4'-cyano-phenyl)methyl)benzene 1 using both ionothermal reaction conditions with ZnCl2 at 400 °C and the milder reaction conditions with the strong Brønsted acid trifluoromethanesulfonic acid (TFMS) at room temperature. Additionally, the hexanitrile was combined with different di-, tri-, and tetranitriles as a second linker based on recent work of mixed-linker CTFs, which showed enhanced carbon dioxide captures. The obtained framework structures were characterized via infrared (IR) spectroscopy, elemental analysis, scanning electron microscopy (SEM), and gas sorption measurements. Nitrogen adsorption measurements were performed at 77 K to determine the Brunauer-Emmett-Teller (BET) surface areas range from 493 m2/g to 1728 m2/g (p/p0 = 0.01-0.05). As expected, the framework CTF-hex6 synthesized from 1 with ZnCl2 possesses the highest surface area for nitrogen adsorption. On the other hand, the mixed framework structure CTF-hex4 formed from the hexanitrile 1 and 1,3,5 tricyanobenzene (4) shows the highest uptake of carbon dioxide and methane of 76.4 cm3/g and 26.6 cm3/g, respectively, at 273 K.

Engineered Bifunctional Luminescent Pillared-Layer Frameworks for Adsorption of CO2 and Sensitive Detection of Nitrobenzene in Aqueous Media

Through a dual-ligand synthetic approach, five isoreticular primitive cubic (pcu)-type pillared-layer metal-organic frameworks (MOFs), [Zn₂ (dicarboxylate)₂ (NI-bpy-44)]⋅x DMF⋅y H₂ O, in which dicarboxylate=1,4-bdc (1), Br-1,4-bdc (2), NH₂ -1,4-bdc (3), 2,6-ndc (4), and bpdc (5), have been engineered. MOFs 1-5 feature twofold degrees of interpenetration and have open pores of 27.0, 33.6, 36.8, 52.5, and 62.1 %, respectively. Nitrogen adsorption isotherms of activated MOFs 1'-5' at 77 K all displayed type I adsorption behavior, suggesting their microporous nature. Although 1' and 3'-5' exhibited type I adsorption isotherms of CO₂ at 195 K, MOF 2' showed a two-step gate-opening sorption isotherm of CO₂ . Furthermore, MOF 3' also had a significant influence of amine functions on CO₂ uptake at high temperature due to the CO₂ -framework interactions. MOFs 1-5 revealed solvent-dependent fluorescence properties; their strong blue-light emissions in aqueous suspensions were efficiently quenched by trace amounts of nitrobenzene (NB), with limits of detection of 4.54, 5.73, 1.88, 2.30, and 2.26 μm, respectively, and Stern-Volmer quenching constants (K_sv ) of 2.93×10³ , 1.79×10³ , 3.78×10³ , 4.04×10³ , and 3.21×10³  m^-1 , respectively. Of particular note, the NB-included framework, NB@3, provided direct evidence of the binding sites, which showed strong host-guest π-π and hydrogen-bonding interactions beneficial for donor-acceptor electron transfer and resulting in fluorescence quenching.

A new electrochemical sensor for the detection of fentanyl lethal drug by a screen-printed carbon electrode modified with the open-ended channels of Zn(ii)-MOF

An electrochemical fentanyl sensor based on modified screen-printed carbon electrode by Zn(ii)-MOF.

From lamellar net to bilayered-lamella and to porous pillared-bilayer: reversible crystal-to-crystal transformation, CO2 adsorption, and fluorescence detection of Fe3+, Al3+, Cr3+, MnO4−, and Cr2O72− in water

Layered coordination polymers of different network topologies have showed reversible structural transformations and fluorescence detection toward Fe³⁺, Al³⁺, Cr³⁺, MnO₄^–, and Cr₂O₇^2– in water.

Spectroelectrochemical studies of the redox active tris[4-(triazol-1-yl)phenyl]amine linker and redox state manipulation of Mn(ii)/Cu(ii) coordination frameworks

In situ spectroelectrochemical methods were conducted to investigate the redox active tris(4-(1H-1,2,4-triazol-1-yl)phenyl)amine (TTPA) ligand and its incorporation into the solid state of Mn(ii) and Cu(ii) frameworks.

Paddlewheel SBU based Zn MOFs: Syntheses, Structural Diversity, and CO₂ Adsorption Properties

Four Zn metal⁻organic frameworks (MOFs), {[Zn₂(2,6-ndc)₂(2-Pn)]·DMF}n (1), {[Zn₂(cca)₂(2-Pn)]·DMF}n (2), {[Zn₂(thdc)₂(2-Pn)]·3DMF}n (3), and {[Zn₂(1,4-ndc)₂(2-Pn)]·1.5DMF}n (4), were synthesized from zinc nitrate and N,N'-bis(pyridin-2-yl)benzene-1,4-diamine (2-Pn) with naphthalene-2,6-dicarboxylic acid (2,6-H₂ndc), 4-carboxycinnamic acid (H₂cca), 2,5-thiophenedicarboxylic acid (H₂thdc), and naphthalene-1,4-dicarboxylic acid (1,4-H₂ndc), respectively. MOFs 1⁻4 were all constructed from similar dinuclear paddlewheel {Zn₂(COO)₄} clusters and resulted in the formation of three kinds of uninodal 6-connected non-interpenetrated frameworks. MOFs 1 and 2 suit a topologic 4⁸·6⁷-net with 17.6% and 16.8% extra-framework voids, respectively, 3 adopts a pillared-layer open framework of 4⁸·6⁶·8-topology with sufficient free voids of 39.9%, and 4 features a pcu-type pillared-layer framework of 412·6³-topology with sufficient free voids of 30.9%. CO₂ sorption studies exhibited typical reversible type I isotherms with CO₂ uptakes of 55.1, 84.6, and 64.3 cm³ g-1 at 195 K and P/P₀ =1 for the activated materials 1', 2', and 4', respectively. The coverage-dependent isosteric heat of CO₂ adsorption (Qst) gave commonly decreased Qst traces with increasing CO₂ uptake for all the three materials and showed an adsorption enthalpy of 32.5 kJ mol-1 for 1', 38.3 kJ mol-1 for 2', and 23.5 kJ mol-1 for 4' at zero coverage.

Ultrasound-assisted synthesis of nano-structured Zinc(II)-based metal-organic frameworks as precursors for the synthesis of ZnO nano-structures

A 3D, porous Zn(II)-based metal-organic framework {[Zn₂(oba)₂(4-bpmn)]·(DMF)_1.5}_n (TMU-21), (4-bpmn=N,N'-Bis-pyridin-4-ylmethylene-naphtalene-1,5-diamine, H₂oba=4,4'-oxybis(benzoic acid)) with nano-rods morphology under ultrasonic irradiation at ambient temperature and atmospheric pressure was prepared and characterized by scanning electron microscopy. Sonication time and concentration of initial reagents effects on the size and morphology of nano-structured MOFs were studied. Also {[Zn₂(oba)₂(4-bpmn)] (TMU-21) and {[Zn₂(oba)₂(4-bpmb)] (TMU-6), 4-bpmb=N,N'-(1,4-phenylene)bis(1-(pyridin-4-yl)methanimine) were easily prepared by mechanochemical synthesis. Nanostructures of Zinc(II) oxide were obtained by calcination of these compounds and their de-solvated analogue as activated MOFs, at 550°C under air atmosphere. As a result of that, different Nanostructures of Zinc(II) oxide were obtained. The ZnO nanoparticles were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR spectroscopy.

Design of a Peripheral Building Block for H-Bonded Dendritic Frameworks and Analysis of the Void Space in the Bulk Dendrimers

Three dendrimers, (t-Bu-G 2 N) 2 , CC(t-Bu-G 1 N) 3 and (t-Bu-G 1 N) 2 , with 3,5-di-tert-butyl amidobenzene as a common peripheral moiety were prepared in 64-83% yields and characterized. The bulk solids had high BET surface areas of 136-138 m2/g, which were similar for the three dendrimers in spite of their different molecular weight (ranging from 1791 to 2890). It was concluded that the peripheral amide groups do not imbed in the interstitial space of neighbouring dendrimer molecules but rather build a supramolecular architecture through strong intermolecular H-bonds. This mode of assembly generates voids in the bulk dendrimers responsible for sorption properties. The X-ray crystal structure analysis of a compound representing the peripheral moiety of the dendrimers and the FT-IR and powder-XRD data for (t-Bu-G 1 N) 2 suggest the proposed supramolecular structure. The isosteric heats of CO2 sorption (Q st) for (t-Bu-G 2 N) 2 were significantly higher than those for the other two dendrimers, which is consistent with the formation of a different type of voids within the interstitial space of the molecule. It is suggested that the interstitial void space can be designed and tuned to adjust its properties to a particular task, such as the separation of gases or a catalytic reaction facilitated by the dendrimer.

Insights into the pores of microwave-assisted metal–imidazolate frameworks showing enhanced gas sorption

Microwave assisted synthesized materials have an inherent ability to trap extra linkers, thereby reducing the pore sizes of CE- heating materials to ultra/micropores. These ultramicropores are responsible for high gas sorption.

Syntheses, structural diversities and characterization of a series of coordination polymers with two isomeric oxadiazol-pyridine ligands

In this work two positional-isomeric oxadiazol-pyridine ligands 3-(5-methyl-1,3,4-oxadiazol-2-yl)pyridine (L₁) and 4-(5-methyl-1,3,4-oxadiazol-2-yl)pyridine (L₂) have been designed and synthesized.

Amides Do Not Always Work: Observation of Guest Binding in an Amide-Functionalized Porous Metal-Organic Framework

An amide-functionalized metal organic framework (MOF) material, MFM-136, shows a high CO₂ uptake of 12.6 mmol g^–1 at 20 bar and 298 K. MFM-136 is the first example of an acylamide pyrimidyl isophthalate MOF without open metal sites and, thus, provides a unique platform to study guest binding, particularly the role of free amides. Neutron diffraction reveals that, surprisingly, there is no direct binding between the adsorbed CO₂/CH₄ molecules and the pendant amide group in the pore. This observation has been confirmed unambiguously by inelastic neutron spectroscopy. This suggests that introduction of functional groups solely may not necessarily induce specific guest–host binding in porous materials, but it is a combination of pore size, geometry, and functional group that leads to enhanced gas adsorption properties.

A series of pyridyl-amide-based ZnII/CdII coordination polymers and their polypyrrole-functionalized composite materials for tuning their photocatalytic properties

Six pyridyl-amide-based Zn^II/Cd^II coordination polymers have been solvothermally synthesized and decorated by polypyrrole for tuning their photocatalytic properties under visible irradiation.

The assembly of thiophene-based bis-pyridyl-bis-amide CoII coordination polymers and their polypyrrole-functionalized hybrid materials for boosting their photocatalytic performances

A series of thiophene-based bis-pyridyl-bis-amide coordination polymers have been synthesized and decorated with polypyrrole for boosting their photocatalytic properties under visible light irradiation.

Sonochemical synthesis of a nano-structured zinc(II) amidic pillar metal-organic framework

A facile and environmentally friendly nano-scale synthesis of a Zn(II) metal-organic framework (MOF), {[Zn4(BDC)4(bpta)4]·5DMF·3H2O}n (1) (bpta=N,N'-bis(4-pyridinyl)-1,4-benzenedicarboxamide, BDC=1,4-dicarboxylate, DMF=N,N-dimethylformamide), with nanorods morphology under ultrasonic irradiation at ambient temperature and atmospheric pressure has been explored. This MOF has been characterized by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD) and IR spectroscopy. Some parameters such as concentration of initial reagents, power ultrasound irradiation and time effects on size and morphology of nano-structured compound 1 have been studied.

Amide-containing zinc(ii) metal–organic layered networks: a structure–CO2 capture relationship

An intimate interrelationship between the structural characteristics and their CO₂ adsorption behavior has been demonstrated in this study.

Structure-directing factors when introducing hydrogen bond functionality to metal–organic frameworks

Introduction of functional groups into an isoreticular series of MOFs may be complicated by noncovalent interactions between interpenetrated nets inducing differing topologies.

Aminopyridine derivatives controlled the assembly and various properties of Cu–BTC metal–organic frameworks

Three Cu(ii) MOFs based on three aminopyridine derivatives and 1,3,5-benzenetricarboxylic acid have been synthesized and characterized. The electrocatalytic and photocatalytic properties of complexes 1–3 have been investigated in detail.

Selective carbon dioxide adsorption by mixed-ligand porous coordination polymers

Mixed ligand metal–organic frameworks (MOFs) have resolutely established themselves as a class of excellent solid state sorbents for carbon dioxide (CO₂) and a proper design of such MOF can potentially improve not only the amount of CO₂ adsorption, but also the selectivity of CO₂ uptake over other gases and volatiles.

A huge diamondoid metal–organic framework with a neo-mode of tenfold interpenetration

A huge diamondoid framework with edge distances of the adamantane cages of up to 25.95 Å, is reported. This MOF displays a tenfold interpenetration, which is constructed from bulky and elongated aromatic-rigid dicarboxylate scaffolds, exhibits a self-catenated net with a point symbol of {(6².8⁴)(6⁴.8.10)₂}.

Assembly, structures, photophysical properties and photocatalytic activities of a series of coordination polymers constructed from semi-rigid bis-pyridyl-bis-amide and benzenetricarboxylic acid

Ten metal–organic coordination polymers 1–10 based on semi-rigid bis-pyridyl-bis-amide ligands have been synthesized. The fluorescence sensing and photocatalytic properties of 1–10 have been investigated.