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Magnetic sustentation experiments are employed to monitor the adsorption process of a supramolecularly assembled MOF in solution.

The sol–gel method provides a simple and versatile synthesis route to prepare low temperature curable metal-organic coatings photocatalytically active by visible light.

The synergistic combination of a zirconium metal–organic cluster and a Keggin type polyoxotungstate led to a chemically stable and photoactive porous material.

UiO-66, reported in 2008, inspired the ongoing chemistry of group 4 metal-organic frameworks and it is still one of the most studied MOFs due to its exceptional stability. The tightness of their building blocks and bond strength make it tough to access new topologies, unless the building blocks are changed or defect engineering is employed, which in turn lead to different nominal stoichiometries. However, well selected structure directing agents and harsh synthesis conditions allowed the isolation of the first polymorph of UiO-66, named EHU-30. Herein, we provide evidence for the generalization of the synthetic approach with four new EHU-30 isoreticular compounds, based on amino-functionalized linkers and zirconium and hafnium as metal centres: EHU-30-NH2(M) and EHU-30-NHR(M) (M: Zr, Hf; R: 2-carboxypropyl). The crystal structure analysis reveals that their framework is more porous than that of their polymorphic counterpart. Furthermore, due to the current relevance of MOFs in greenhouse gas capture and in water harvesting methodologies, we have explored CO2 and water vapour adsorption on the new polymorphic phases, by means of experimental and computational resources, and compared to the parent EHU-30. The amino functionalization makes the EHU-30 series more prone to CO2 and water vapour adsorption. Besides, the water adsorption isotherms show an interesting crossing sensitive to temperature, sorption cycles and functionalization of the linker, which has been attributed to a localized structural transformation from EHU-30 to UiO-66. Finally, time-of-flight (TOF) powder neutron diffraction experiments were also conducted to locate the preferred adsorption sites for water in functionalized and parent EHU-30 structures.

Metal-organic frameworks (MOFs) imply an appealing source of photocatalysts as they combine porosity with tailorable electronic properties and surface chemistry. Herein, we report a series of unprecedented metal-organic aerogels (MOAs) comprised by Ti(IV) oxo-clusters and aromatic dicarboxylic linkers as an alternative to microporous MIL-125 and MIL-125-NH2 MOFs. Discrete titanium oxo-clusters polymerized upon the addition of the dicarboxylic linkers to give rise to a metal-organic gel. Their supercritical drying led to aerogels comprised by nanoscopic particles (ca. 5-10 nm) cross-linked into a meso/macroporous microstructure with surface area ranging from 453 to 617 m2 center dot g-1, which are comparatively lower than the surface area of the microporous counterparts (1336 and 1145 m2 center dot g-1, respectively). However, the meso/macroporous microstructure of MOAs can provide a more fluent diffusion of reagents and products than the intrinsic porosity of MOFs, whose narrower channels are expected to imply a more sluggish mass transport. In fact, the assessment of the continuous visible-light-driven photocatalytic CO2 reduction into methanol shows that MOAs (221-786 mmol center dot g-1 center dot h-1) far exceed not only the performance of their microporous counterparts (49-65 mmol center dot g-1 center dot h-1) but also surpass the production rates provided by up-to-date reported photocatalysts. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Oscar Castillo and Jonathan Albo report financial support was provided by Basque Government. Oscar Castillo and Estibaliz Aranzabe report financial support was provided by Spanish Ministry of Science and Innovation. Estibaliz Aranzabe reports financial support was provided by European Union. The authors gratefully acknowledge the financial support from the European Union's Horizon 2020 research and innovation program (grant agreement No.101037428), the Basque Government (KK-2016/00095-LISOL IT1291-19 and IT1722-22) and the Spanish Ministry of Science and Innovation (TED2021-129810B-C21 and TED2021-129810B-C22 funded by MCIN/AEI/10.13039/501100011033 and Next Generation EU/PRTR, PID2019-108028GB-C21 and PID2019-104050RA-I00 funded by MCIN/AEI/10.13039/501100011033). Technical and human support provided by SGIker (UPV/EHU, MICINN, GV/EJ, and ESF) is also acknowledged.

Clustering chemistry is a key point in the design and synthesis of the secondary building units that comprise metal-organic frameworks (MOFs) based on group IV metals. In this work, the first stages of the zirconium-carboxylate clustering process in alcohol/water mixtures are studied in detail using the monocarboxylic benzoic and hydroxybenzoic acids to avoid the polymerization. Mass spectroscopy measurements performed on the reactions revealed the presence of hexa- and pentanuclear species even at low pH values and also evidenced the acid-base nature and pH dependence of the transformation between both species. The control on the chemistry governing the equilibria between these species has allowed us to isolate six new compounds in the solid state. The single-crystal X-ray diffraction analysis revealed that they are closely related to the well-known [Zr

Scientific reports 12(1), 8505 (2022). doi:10.1038/s41598-022-11846-w, The doping of zirconium based EHU-30 and EHU-30-NH$_2$ metal–organic frameworks with copper(II) yielded a homogeneous distribution of the dopant with a copper/zirconium ratio of 0.04–0.05. The doping mechanism is analysed by chemical analysis, microstructural analysis and pair distribution function (PDF) analysis of synchrotron total scattering data in order to get deeper insight into the local structure. According to these data, the Cu(II) atoms are assembled within the secondary building unit by a transmetalation reaction, contrarily to UiO-66 series in which the post-synthetic metalation of the MOF takes place through chemical anchorage. The resulting materials doubled the overall performance of the parent compounds for the CO$_2$ electroreduction, while retained stable the performance during continuous transformation reaction., Published by Macmillan Publishers Limited, part of Springer Nature, [London]

Correction for ‘An in solution adsorption characterization technique based on the response to an external magnetic field of porous paramagnetic materials: application on supramolecular metal–adenine frameworks containing heterometallic heptameric clusters’ by Jon Pascual-Colino et al., Inorg. Chem. Front., 2023, https://doi.org/10.1039/d2qi01994a.

Reactions of N-methylated adenine (9-methyladenine and 3-methyladenine) with water-soluble oxalato complexes in the presence of potassium oxalate yields a series of oxalato-bridged complexes with the nucleobases as pendant ligands whose crystal structures and magnetic properties are reported herein. The complexes [M2(µ-ox)2(9Meade)3]n [M(II) = Zn (1), Cu (2); where ox = oxalato and 9Meade = 9-methyladenine] are composed of infinite corrugated one-dimensional chains in which two types of metal(II) centres are sequentially bridged by asymmetric bis-bidentate oxalato ligands and their coordination polyhedra are filled by N7-coordinated 9-methyladenine molecules giving rise to two different chromophores: an octahedral N2O4 donor set with the nucleobase moieties in trans-arrangement, and square based pyramidal NO4 coordination polyhedra. The cohesiveness of their supramolecular 3D architectures is achieved by means of an extensive network of non-covalent interactions including a short contact between the minor groove N3 site of the model 9-methyladenine and the oxalato bridging ligand from a neighbouring chain. This unconventional interaction between the lone pair of the pyrimidinic nitrogen atom of the nucleobase and the π-system of the oxalate anion has been analysed and discussed in the light of available structural data for analogous systems. The compounds {[M(µ-ox)(H2O)(3Meade)]·H2O}n [M(II) = Zn (3), Co (4) and Mn (5); where 3Meade = 3-methyladenine], and {[Cu(µ-ox)(3Meade)2]·4H2O}n (6) are comprised of zig–zag metal-oxalato chains, with the oxalato adopting a symmetric bis-bidentate coordination mode. The octahedral environment of the metals is completed in a cis-arrangement by one water molecule and the imidazole N7 donor site of a 3-methyladenine ligand for 3–5, and by two N7-coordinated nucleobases for 6. The crystal packing of the chains leads to the presence of channels with dimensions of 5 × 10 A for 6, and 4 × 6 A for 3–5 which are occupied by crystallization water molecules. The non-covalent interactions of the nucleobases among them and with the metal-oxalato framework have been studied in detail as well as the magnetic interactions mediated by the bridging oxalato ligand.

Herein, we report on the synthesis, structural analysis, physicochemical characterization and photoluminescence performance of two ternary compounds based on dicarboxylate and bispyridyl-like ligands and metal ions of group 12, namely [Zn2(μ4-bdc)(μ-pbptz)(DMF)2(NO3)2]n (1-Zn) and {[Cd(μ3-bdc)(μ-pbptz)]·DMF}n (2-Cd) (where bdc = benzene-1,4-dicarboxylate, pbptz = 3,6-bis(4-pyridyl)-1,2,4,5-tetrazine, and DMF = N,N-dimethylformamide). 1-Zn, consisting of a 2D-layered framework, can be considered as the lower-dimensional analogue of the previously reported {[Zn2(μ4-bdc)2(μ-pbptz)]·2DMF·3H2O}n 3D MOF (1′-Zn), which is shown to recrystallize into 1-Zn undergoing a kind of exfoliation. 2-Cd presents a 3D doubly interpenetrated framework whose porosity is reduced to approximately half of the available solvent-accessible voids contained in the non-interpenetrated homologue reported so far, {[Cd(μ3-bdc)(μ-pbptz)]·3DMF}n (2′-Cd). Structural factors leading to each of the alternative frameworks are detailed by analysing the building units with a perusal of the Cambridge Structural Database and providing a comparative description of the structures. The photoluminescence properties of herein reported compounds (1-Zn and 2-Cd) are also measured and the processes governing the spectra are described using time-dependent density-functional theory (TD-DFT), which allows establishing some structural correspondences by comparing these results with those of the 1′-Zn and 2′-Cd analogues.

The slot-die process is an appealing technology for the fabrication of coatings on large-area substrates. However, its application on the production of photocatalytic coatings based on sol–gel formulations remains virtually unexplored. Thus, assessing the suitable formulation of the sol and operational parameters that allow one to yield high-efficacy photocatalyst coatings is a current challenge. This work aims to analyze the transferability of titania sol formulation optimized for dip-coating processes to slot-die technology. In this sense, firstly, the sol formulation is optimized by analyzing the influence of several types of surfactants on the microstructural features and photoactivity of TiO2 coatings’ growth on glass substrates. All formulations rendered a meaningful porosity and nanoscopic anatase crystallites (11–15 nm) with optical band gap values close to the expectation (3.25–3.31 eV). Accordingly, the performance of the photocatalytic dye degradation was closely related to the porosity and crystallite size led by each titania sol, and no meaningful differences were found between the results provided by the coatings developed by dip-coating and the slot-die method, which demonstrates the capability of the latter for its application on a large-scale fabrication of photocatalytic coatings. This research was funded by the Basque Government (IT1291-19), the Spanish Ministry of Science and Innovation (MICINN project: PID2019-108028GB-C21), and the European Union’s Horizon 2020 research and innovation program (grant agreement N° 792103 SOLWARIS).

Summary Using a photocatalytic window can simplify the design of an optofluidic microreactor, providing also a more straightforward operation. Therefore, the development of TiO2 coatings on glass substrates seems appealing, although a priori they would imply a reduced accessible area compared with supported nanoparticle systems. Considering this potential drawback, we have developed an endurable photocatalytic window consisting on an inner protective SiO2 layer and an outer mesoporous anatase layer with enhanced surface area and nanoscopic crystallite size (9–16 nm) supported on a glass substrate. The designed photocatalytic windows are active in the CO2-to-methanol photocatalytic transformation, with maximum methanol yield (0.52 μmol·h−1·cm−2) for greatest porosity values and minimum crystallite size. Compared with benchmark supported nanoparticle systems, the nanoscopic thickness of the coatings allowed to save photoactive material using only 11–22 μg·cm−2, while its robustness prevented the leaching of active material, thus avoiding the decay of performance at long working periods., Graphical abstract, Highlights • Photocatalytic windows provide enhanced operation of optofluidic microreactors • Use of TiO2 nanometric coatings reduces the required photocatalyst amount • The robustness of the coating implies stability upon long-working periods • CO2-to-CH3OH conversion performance is related to the porosity and crystallite size, Chemistry; Catalysis; Engineering

Capture and sensing of emerging pollutants is one of the increasing environmental concerns due to the adverse ecological and human health effects. Here, we report the synthesis of a supramolecular metal-organic framework (SMOF) [CrCu6(m-H2O)6(m3-OH)6(m-adeninato-kN33:kN9)6](SO4)1.5 which is able to capture anionic drugs and exhibits magnetic properties useful for sensing purposes. The features of the nucleobase decorated CrCu6 building block allow the incorporation of up to 9 drug molecules (i.e., ibuprofen and naproxen in this work) per heptameric entity. In addition, we provide a simple way to quantify the incorporated number of drug molecules through a magnetic sustentation experiment in which the field required to keep the particles attached to the electromagnet pole is linearly related to the total mass of the anionic counterion. In this way, it also provides an easy way to determine the amount of entrapped drug molecules, making this SMOF a promising candidate for environmental remediation technologies. This work has been funded by the Universidad del País Vasco/Euskal Herriko Unibertsitatea (GIU17/50), the Gobierno Vasco/Eusko Jaurlaritza (PIBA18/14; IT1291-19), the Ministerio de Economía y Competitividad (MAT2016-75883-C2-1-P), the Ministerio de Ciencia e Innovación (PID2019-108028GB-C21), and FEDER funds. Technical and human support provided by SGIker (UPV/EHU, MICINN, GV/EJ, and ESF) is also acknowledged.

Six novel coordination polymers (CPs) based on alkaline-earth (AE) metal ions and two sorts of aminonicotinate ligands, namely [M(μ-2ani)(μ3-2ani)(μ-DMF)]n [MII = Sr (1) and Ba (2)], {[M(μ-6ani)2(H2O)2]·3H2O}n [MII = Ca (3) and Sr (4)], {[Ca(μ-6ani)2(H2O)2]}n (5) and {[Ba(6ani)2(H2O)3]·7H2O}n (6) [where 2ani = 2-aminonicotinate and 6ani = 6-aminonicotinate] have been synthesized and well characterized. All compounds are firstly built up with AE-carboxylate infinite rods that provide compact 2D-layered structures in 1 and 2 but open architectures containing microchannels in an AE-6ani system. Interestingly, the architecture of 3 behaves as a flexible platform which undergoes spontaneous dehydration to yield compound 5. Structural transition occurring from 3 to 5 has been supported by periodic density functional theory (DFT) calculations and X-ray diffraction data. In this regard, compound 6 contains a high amount of solvent molecules which suggests the existence of pores in its structure. A deep study of the optical properties including a detailed experimental characterization and DFT based computational calculations of these compounds supports a fascinating photoluminescence performance which entails a bright blue emission accompanied by persistent green afterglows at low temperature, especially for compound 5 as reflected by its lifetime (τ ≈ 1.4 s). In addition to its strong room temperature emission properties, we took advantage of the open yet stable structure of compound 4, to check its viability as a new material sensitive to the presence of solvents and/or transition metal ions, via significant quenching of the luminescence of 4. Remarkably, 4 is shown to be a particularly efficient sensor for some water soluble pollutants.

Since its discovery in 2008, the paradigmatic UiO-66 has behaved as the germ that has prompted the chemistry of group-4 metal based metal–organic frameworks, all of them featuring outstanding thermal and chemical stability. Herein we present the first polymorph of UiO-66 and the key conditions that led to its formation.

This work is aimed at the analysis of the interactions that drive the assembling of coordination metal-organic polymers based on biological molecules. Single-crystal X-ray diffraction data show that the compound 1D-{[Cu2(μ-ade)4(H2O)2]·2[Cu(theoph)2]·∼10H2O}n (1) contains neutral rhomboid shaped chains sustained by the tridentate μ3-κN3:κN7:κN9 coordination mode of the adenine nucleobase. These chains are formed by dimeric copper/adeninato (ade) cores doubly bridged by monomeric copper/theophyllinato (theoph) entities with the alkaloid acting as peripheral ligand. The lack of direct intermolecular nucleobase···nucleobase interactions, due to their disruption by the crystallization water molecules, does not provide a highly porous material, but the irregular shape of the polymeric chain hinders their packing and allows the presence of a moderate amount of voids (16% of the unit cell volume) in good accordance with its adsorption capacity of 0.38 mmol CO2/g at 273 K. Thermogravimetric and variable temperature X-ray diffraction analyses show that the compound retains its structure up to 110 °C whereas above this temperature the release of the coordination water molecules produces a significant loss of crystallinity. Magnetic measurements indicate an overall antiferromagnetic behavior with a J value of −267 cm−1 within the dimeric entity.

This work is aimed at the analysis of the π–π stacking interactions as the driving force to develop porous supramolecular metal–organic frameworks (SMOFs) as an alternative to more directional hydrogen bonding interactions. Four compounds based on the interaction between rigid copper/adenine entities and theobromine/caffeine molecules have been synthesized: [Cu7(μ-ade)6(μ3-OH)6(μ-H2O)6](theo)2·∼28H2O (1), [Cu2(μ-ade)4(H2O)2]·3Htheo·∼7H2O (2), [Cu2(μ-ade)4(H2O)2]·2Htheo·∼18H2O (3), and [Cu2(μ-ade)4(H2O)2]·(caf)·∼6H2O (4). The blue compound 1 is formed by wheel-shaped cationic heptameric units where the copper atoms are bridged by hydroxide anions, water molecules, and adeninato ligands with a μ-κN3:κN9 coordination mode. The assembly of the heptameric entities and the theobrominate anions takes place mainly through π–π stacking interactions involving the adeninato ligands and theobrominate moieties. Although compound 1 exhibits an open-framework with voids representing 37% of the unit cell, the plasticity ...

Two novel coordination polymers (CPs) based on zinc(II) and acyclic dicarboxylate linkers, i.e. [Zn2(μ3-IA)2(H2O)4]n (1-W) and {[Zn2(μ-IA)2(DMF)]·H2O}n (2-DMF) (where IA2− = itaconate) have been obtained as a result of a systematic study of some synthetic factors such as pH and solvents, which has allowed optimizing the conditions that render the best yields. 1-W is obtained as X-ray quality single crystals upon which diffraction analysis has been conducted, showing that it consists of a neutral 2D layered structure. Some structural details have been elucidated for 2-DMF based on a comparison of PXRD data with 1-W and in view of the similar composition of both crystalline phases. Photoluminescence (PL) measurements confirm that 2-DMF presents slightly different spectra from those of 1-W. Time-dependent density functional theory (TD-DFT) calculations of 1-W reveal that electronic transitions arise from both first excited singlet and triplet states involving ligand-centred emissions. Moreover, both compounds exhibit blue fluorescence and green phosphorescence that involves less frequent long-lasting phosphorescence (LLP) at 10 K. Exhaustive characterization of long-lasting phosphorescence by means of time-resolved spectroscopy reveals remarkably long lifetimes (τ) of ca. 352 ms (λem ≈ 550 nm) for 1-W and 547 ms (λem ≈ 500 nm) for 2-DMF.

Nucleobases are known as suitable builders of porous materials not only due to their high number of heteroatoms leading to different coordination modes, but also because they establish strong and predictable supramolecular interactions. In this contribution, nucleobases (adenine and guanine), functionalized nucleobases (9-methyladenine) and nucleobase derivatives (6-chloropurine) have been evaluated as ligands for the construction of metal–nucleobase building blocks which can afford supramolecular porous materials, analyzing in detail the requirements that these entities must fulfill and pointing out the relevance of accomplishing the suggested requisites. More concisely, we have evaluated a paddle-wheel shaped dimeric entity, [Cu2(μ-Hade)4Cl2]Cl2·8H2O (1) (where Hade: adenine), a trimeric unit, [Co3(μ-Hade)2(μ-Cl)4Cl2(H2O)4]·2H2O (2), a dimeric entity, [Cu2(Hgua)2(H2gua)2(μ-Cl)2Cl2(H2O)][CuCl4] (3) (where Hgua: guanine, H2gua: guaninium), a monomeric unit with 9-methyladenine as the pendant ligand, [Co(9-Meade)2(H2O)4]Cl2·2H2O (4), zigzag chains, [Cu2(μ-CH3COO)4(μ-9-Meade)]n·nCH3OH (5), and a monomeric unit with 6-chloropurinato ligands, [Co(6-Clpur)2(H2O)4]·4H2O (6).

The use of diazinedicarboxylate ligands in the construction of preconceived molecular entities and crystal structures deserves a good understanding of their coordination capacity in order to employ them for their rational design of functional materials. Therefore, the scope of the present review is to provide a comprehensive account of the architectures built up from these ligands rationalizing them through a conscientious analysis of their coordination modes in which the preponderance for establishing double chelating five-member rings holds a central role. The study covers the coordination features offered by transition, representative and lanthanide metal ions, with special emphasis on the coordination mode prevalence for each ligand. The structural rationalization is assessed during the examples along with their more relevant properties.

EnglishMetal-organic frameworks (MOFs) and supramolecular metal-organic frameworks (SMOFs) are porous crystalline materials which have become a very sub-stantial field of research over the last years. These materials consist of inorganic nodes (isolated metal atoms or metal clusters) which are linked by organic ligands (organic molecules). Nucleobases are suitable ligands since they provide porous metal-organic materials by means of coordination (MOF) or hydrogen-bonding interactions (SMOF). euskaraAzken urteotan konposatu metal-organiko porotsuek (MOFs, metal-or-ganic frameworks, eta SMOFs, supramolecular metal-organic frameworks ingelesez) hazkunde nabarmena izan dute. Konposatu horien egitura kristalinoak estekatzaile or-ganikoen (molekula organikoak) bidez lotutako nodo ez-organikoez (atomo edo kluster metalikoak) eraikita daude. Nukleobaseak gai dira estekatzaile organiko gisa aritu eta material metal-organiko porotsuak emateko, koordinazio- (MOF) zein hidrogeno-lotu-ren (SMOF) bitartez.

Detailed structural characterization and photoluminescence properties of four new metal–organic frameworks (MOFs) based on zinc(II) or cadmium(II) metal ions, di- or tricarboxylic aromatic ligands, and bipyridyl-like elongated ancillary linkers, namely, {[Zn2(μ4-bdc)2(μ-pbptz)]·2DMF·3H2O}n (1), {[Cd(μ3-bdc)(μ-pbptz)]·3DMF}n (2), {[Cd3(μ5-btc)2(μ-pbptz)]·2DMF}n (3), and {[Zn2(μ-dhbdc)2(μ-pbptz)(DMF)4]·2DMF·H2O}n (4) (where bdc = benzene-1,4-dicarboxylato, btc = benzene-1,3,5-tricarboxylato, dhbdc = 2,5-dihydroxobenzene-1,4-dicarboxylato, pbptz = 3,6-bis(4-pyridyl)-1,2,4,5-tetrazine, DMF = N,N-dimethylformamide) are reported. The occurrence of large accessible volumes and structural and topological diversity are a constant for crystal structures of these compounds, which is a result of the connectivity established among the metal-carboxylato building units formed in each case. Three-dimensional (3D) pcu frameworks of compounds 1 and 2 are built from the linkage of dimeric cores (established by the coordinat...

In this work, three isostructural metal-organic frameworks based on first row transition metal ions and 2-aminoisonicotinate (2ain) ligands, namely, {[M(μ-2ain)]·DMF} [M = Co (1), Ni (2), Zn (3)], are evaluated for their sensing capacity of various solvents and metal ions by monitoring the modulation of their magnetic and photoluminescence properties. The crystal structure consists of an open diamond-like topological 3D framework that leaves huge voids, which allows crystallizing two-fold interpenetrated architecture that still retains large porosity. Magnetic measurements performed on 1 reveal the occurrence of field-induced spin-glass behaviour characterized by a frequency-independent relaxation. Solvent-exchange experiments lead successfully to the replacement of lattice molecules by DMSO and MeOH, which, on its part, show dominating SIM behaviour with low blocking temperatures but substantially high energy barriers for the reversal of the magnetization. Photoluminescence studied at variable temperature on compound 3 show its capacity to provide bright blue emission under UV excitation, which proceeds through a ligand-centred charge transfer mechanism as confirmed by time-dependent DFT calculations. Turn-off and/or shift of the emission is observed for suspensions of 3 in different solvents and aqueous solutions containing metal ions., This work has been funded by Red Guipuzcoana de Ciencia, Tecnología e Innovación (OF218/2018), University of the Basque Country (GIU 17/13), Gobierno Vasco/Eusko Jaurlaritza (IT1005-16, IT1291-19, IT1310-19), Junta de Andalucía (FQM-394) and the Spanish Ministry of Science, Innovation and Universities (MCIU/AEI/FEDER, UE) (PGC2018-102052-A-C22, PGC2018-102052-B-C21, MAT2016-75883-C2-1-P). The authors thank for technical and human support provided by SGIker of UPV/EHU and European funding (ERDF and ESF). Dr. Iñigo López Arbeloa and Dr. Virginia Martínez Martínez are greatly acknowledged for their generous collaboration with quantum yield measurements.

Zirconium based metal-organic gels are obtained through a rapid method at room temperature, employing green solvents, in which the role of water is important. These porous materials, decorated with Brønsted acid sites, show outstanding thermal and chemical stability prompting them as stable catalyst in the continuous electroreduction of CO2. This research has been funded by Ministerio de Economía y Competitividad (MAT2016-75883–C2–1–P) and Universidad del País Vasco/Euskal Herriko Unibertsitatea (PPG17/37). J. Albo acknowledges the Ramón y Cajal programme (RYC-2015-17080). The authors thank for technical and human support provided by SGIKer of UPV/EHU and European funding (ERDF and ESF)

Two planar organic anions, benzoate and benzene-1,4-dicarboxylate (terephthalate), have been selected as potential π-stacking intercalators among ferrimagnetic [Cu7(μ-adeninato)6(μ3-OH)6(μ-H2O)6]2+ heptameric discrete entities. The resulting supramolecular architecture is highly dependent on the negative charge density distribution, mainly located in the carboxylate groups of the organic anions. In this sense, the benzoate anion, with just one carboxylate group, does not allow its intercalation between the adeninato ligands as it would imply a high steric hindrance among the heptameric entities. As a consequence, these benzoate anions are located inside the voids of the crystal structure reducing the accessible volume of compound [Cu7(μ-adeninato)6(μ3-OH)6(μ-H2O)6](benzoate)2·~17H2O (1). On the contrary, the terephthalate anion, containing two carboxylate groups at opposite sites, adopts a π-stacking sandwich arrangement between two adeninato ligands that affords the porous open structure of formula [Cu7(μ-adeninato)6(μ3-OH)6(μ-H2O)6](terephthalate)·nH2O (2a, 2b; n: 12 and 24, respectively). In addition to that, the less directional nature of the π-stacking interactions in comparison to the complementary hydrogen bonding based supramolecular metal-organic frameworks (SMOFs), suits them with a flexible architecture able to reversibly adsorb/desorb water (up to a 25–30% at 20 °C) altogether with the expansion/shrinkage of the crystal structure. The bridging adeninato and hydroxido ligands are effective magnetic exchange mediators to provide a ST = 5/2 ferrimagnetic state for the heptanuclear entity.

Since its discovery in 2008, the paradigmatic UiO-66 has behaved as the germ that has prompted the chemistry of group-4 metal based metal-organic frameworks, all of them featuring outstanding thermal and chemical stability. Herein we present the first polymorph of UiO-66 and the key conditions that led to its formation.

Five new compounds of cytosine with first-row transition metals, (H2Cyt)2[CoCl4]·2(HCyt) (1), [CoBr2(HCyt)2] (2), [ZnCl2(HCyt)2] (3), [CuCl2(HCyt)2] (4), and [CuBr2(HCyt)2] (5) (in which HCyt = cytosine, H2Cyt = cytosinium cation), are reported. In 1, the protonation of one of the cytosine molecules facilitates base pairing with the neutral cytosine, instead of the expected coordination to the metal center. In all other compounds, neutral cytosine molecules are coordinated to the MII centers through N3 positions, forming monomeric entities. The supramolecular crystal structure of 1 is sustained by the base-pairing interactions between the 1H,3H-cytosinium cation and the neutral 1H-cytosine molecule through their Watson–Crick and sugar edges, giving rise to zig-zag supramolecular ribbons, in which neutral and cationic cytosine molecules alternate. In the isostructural compounds 2 and 3, only one of the cytosine molecules establishes base pairing through sugar-edge-forming supramolecular dimers, and the 3D cohesiveness is achieved by means of noncomplementary hydrogen bonding, involving the sugar edge of the other cytosine with the amino group and the bromide anions of the adjacent dimer. Compounds 4 and 5 show similar supramolecular arrangements, with cytosine molecules self-assembling along the sugar edge into 1D chains.

We report herein the synthesis and structural and chemical characterization of six new compounds consisting of 6-aminonicotinate (6ani) ligands and first-row transition metal ions, namely, [Mn2(μ-6ani)2(H2O)8](6ani)2 (1), [Co(6ani)(bipy)2(H2O)3](6ani)·5H2O (2), [M(μ-6ani)(6ani)(H2O)3]·2H2O [MII = Co (3), Ni (4)], and [M(μ-6ani)2]·H2O [MII = Co (5), Cu (6)] (where bipy = 4,4′-bipyridine). Compounds 1 and 2 consist of isolated dimeric and monomeric entities held together by supramolecular interactions governed by 6ani free anions. The rigid and low symmetry of 6ani ligands, in addition to their coordination as terminal and bridging ligands to octahedral metal geometries, gives rise to chiral 1D chains of compounds 3 and 4. 2D sql layers are formed (5 and 6) when 6ani ligands act as ligands bridging the metal ions, which precludes the presence of water molecules in the framework. Despite the wide structural diversity observed, all architectures share the occurrence of magnetically isolated 3d metal ions, given the poor exchange achieved through 6ani bridges, as confirmed by dc susceptibility measurements and DFT calculations. Dynamic ac susceptibility measurements reveal best-in-class field-induced slow magnetic relaxation behaviour in Co-based compounds with easy-plane magnetic anisotropy. The effective energy barriers (Ueff) of 39.6 K and 18.7 K for 3 and 5, respectively, estimated using the Arrhenius law are remarkably high among CoII-SIM coordination polymers reported so far.

The nucleophilic attack of a series of nucleobase derivatives on the [(η6-p-cymene)RuCl(μ-Cl)]2 dinuclear entity has yielded four mononuclear complexes with the general formula [Ru(η6-p-cymene)(L)Cl2], in which L stands for cytosine (1), 2-thiouracil (2), hypoxanthine (3) and 5-aminouracil (4). Furthermore, the sieving of chlorido from compound 1, assisted by a mild base, has prompted the formation of a tetranuclear ruthenium cationic complex which crystallizes as [(η6-p-cymene)4Ru4(μ-cytosinato-κN1:κN3,O2)4](CF3SO3)4 (compound 5). The crystal structure analysis of compounds 1–4 reveals that the supramolecular packing is dominated by the self-assembly capabilities provided by the stabilized nucleobase-tautomer, which is at the same time dependent on the Ru/nucleobase coordination mode. In this regard, the assembly of the complex units is conducted through base-pairing interactions, and is also assisted by means of nucleobase/chloride hydrogen bonding. The stability of these monomeric entities in water and phosphate buffered solution is analysed by means of 1H- and 31P-NMR. The tetranuclear entity of compound 5 presents an available hydrogen-donor set (exocyclic amino group) but it lacks any available acceptor atom, which prevents the nucleobase mediated self-assembly of the complex units. Consequently, a doubly interpenetrated supramolecular network is woven by the hydrogen bonding between the triflate (CF3SO3−) anions and complex cationic entities.

The present work deals with the design and construction of supramolecular extended systems built up from paddle-wheel shaped metal–adeninate entities in which the deprotonation of the adenine affords a neutral [Cu2(μ-ade-κN3:κN9)4(H2O)2] (ade: adeninate anion) that would avoid the presence of counterions in the channels of the generated supramolecular architecture as happens for the cationic [Cu2(μ-Hade)4(X)2]2+ (Hade: adenine) entity. This strategy allows us to obtain a new compound of formula 3[Cu2(μ-ade-κN3:κN9)4(H2O)2]·2{(NHEt3)2(SO4)}·10H2O·2CH3OH (1) in which the assembly of the neutral dimeric entities gives rise to an open 3D supramolecular architecture with a 45% of void volume. However, such a great available space allows its interpenetration by a second, although different, network of the same neutral [Cu2(μ-ade-κN3:κN9)4(H2O)2] entities assembled into 1D linear chains. The remaining available space within the channels is occupied by triethylammonium cations, sulphate anions, crystallization water and methanol molecules. The resulting crystal structure has been rationalized in terms of the rigidity of the building block, the predictability and rigidity of the synthons and the arrangement of these synthons around the metal–nucleobase discrete entity. The thermal and magnetic characterization of the compound has been also accomplished.

The present work provides two new examples of supramolecular metal-organic frameworks consisting of three-dimensional extended noncovalent assemblies of wheel-shaped heptanuclear [Cu7(μ-H2O)6(μ3-OH)6(μ-adeninato-κN3:κN9)6](2+) entities. The heptanuclear entity consists of a central [Cu(OH)6](4-) core connected to six additional copper(II) metal centers in a radial and planar arrangement through the hydroxides. It generates a wheel-shaped entity in which water molecules and μ-κN3:κN9 adeninato ligands bridge the peripheral copper atoms. The magnetic characterization indicates the central copper(II) center is anti-ferromagnetically coupled to external copper(II) centers, which are ferromagnetically coupled among them leading to an S = 5/2 ground state. The packing of these entities is sustained by π-π stacking interactions between the adenine nucleobases and by hydrogen bonds established among the hydroxide ligands, sulfate anions, and adenine nucleobases. The sum of both types of supramolecular interactions creates a rigid synthon that in combination with the rigidity of the heptameric entity generates an open supramolecular structure (40-50% of available space) in which additional sulfate and triethylammonium ions are located altogether with solvent molecules. These compounds represent an interesting example of materials combining both porosity and magnetic relevant features.

Several synthetic approaches have been employed to obtain novel {[ScM(μ4-pmdc)2(H2O)2]·solv}n [EHU1(Sc,M)] (where M = Li, Na; pmdc = pyrimidine-4,6-dicarboxylate; solv = corresponding solvent) compounds. The synthesis method is crucial to determine the type of alkaline that could be hosted in the structure as well as the crystallinity, adsorption performance, and ionic conductivity of the resulting materials. Compared with other synthetic methods, a heat-assisted solvent-free procedure has proven to be the most effective route, giving materials with adsorption capacities close to those expected from GCMC (Grand Canonical Monte Carlo) calculations. Despite the presence of alkaline ions in the framework, the pristine materials exhibit rather low conductivity values of ca. 10–7 S cm–1. The concentration of charge carriers has been increased by means of a doping approach that incorporates divalent transition metal ions to the structure and forces an increase of the alkaline ions, thus raising the ionic conduc...

espanolThe use of nanotechnology has become a key tool for the development of an endless number of applications. The food sector is not an exception since the bene-fits of nanotechnology are expected to allow us to enjoy healthier, more resilient and long-lasting foods. In this work, we present the main advances related to the introduc-tion of nanotechnology in the food sector, focusing on three areas: nano-enriched foods, novel designs for food packaging and nanosensors. Finally, the controversy sur-rounding nanofood is analyzed, since although nanotechnology can contribute with lots of benefits, its use still causes fear and insecurity among the population. euskaraNanoteknologiaren erabilpena funtsezko erreminta bilakatu da apli-kazio askoren garapenean, eta elikagaien sektorea ez da alde batera geratu. Modu ho-rretan, nanoelikagaien garapenak osasuntsuagoak, erresistenteagoak eta iraupen luzea-goa duten elikagaiz gozatzea ahalbidetuko duela uste da. Lan honetan, nanoteknologia elikadura sektorean ezartzeak eragindako aurrerapen nagusiak aurkezten dira eta, be-reziki, honako hiru arlo hauetan jarri da arreta: nano-aberastutako elikagaiak, elikagai biltegiratzeko diseinu berriak eta nanosentsoreak. Amaitzeko, elikadura industrian na-noteknologiaren erabilpenak eragindako eztabaida aztertuko da; abantaila asko ekar di-tzakeen arren, egun gizartearengan beldurra eta kezkak eragiten baititu.

Invited for the cover of this issue is the group of Oscar Castillo at the University of the Basque Country (UPV/EHU) in Bilbao, Spain. The cover image shows the colors emitted by polycrystalline samples of a series of 3D coordination compounds comprising yttrium(III) metal ions and pyrimidine-4,6-dicarboxylato and oxalato ligands when they are doped with europium(III) and terbium(III) ions. The color of the emission can be tuned by changing the amount of doping, varying the excitation wavelength, and/or monitoring the dehydration/rehydration of the channels.

Herein we report the solventless synthesis and doping of the benchmark HKUST-1(Cu) as a facile route to afford heterometallic metal-organic frameworks (MOFs) having proficient behavior as electrocatalytic materials in the reduction of carbon dioxide. Zn(ii), Ru(iii) and Pd(ii) were selected as doping metals (M

Herein we report the solventless synthesis and doping of the benchmark HKUST-1(Cu) as a facile route to afford heterometallic metal?organic frameworks (MOFs) having proficient behavior as electrocatalytic materials in the reduction of carbon dioxide. Zn(II), Ru(III) and Pd(II) were selected as doping metals (MD) with the aim of partially replacing the Cu(II) atoms of the pristine structure to afford HKUST-1(Cu,MD) type materials. Apart from the high yield and good crystallinity of the obtained materials, the extremely high reagent concentration that the reaction conditions imply makes it feasible to control dopant loading in all cases. Prepared samples were processed as electrodes and assembled in a continuous flow filter-press electrochemical cell. Faraday efficiency to methanol and ethanol at Ru(III)-based electrodes resulted in activity as high as 47.2%, although the activity of the material decayed with time. The interplay of the dopant metal and copper(II), and the long-term performance are also discussed. This work has been funded by the Universidad del País Vasco/Euskal Herriko Unibertsitatea (GIU17/50 and PP617/37) and Ministerio de Economía y Competitividad (MAT2016-75883-C2-1-P and CTQ2016-76231-C2-1-R). J. Albo acknowledges the Ramón y Cajal programme (RYC-2015-17080). Technical and human support provided by SGIker (UPV/EHU, MICINN, GV/EJ, ESF) is also acknowledged.

The present work provides the basis to obtain three-dimensional (3D) extended porous supramolecular assemblies named supramolecular metal–organic frameworks (SMOFs). This goal can be achieved by considering three key factors: (i) the use of rigid building units, (ii) the establishment of predictable and rigid synthons between the building units, and (iii) the non-coplanarity of functional groups involved in the predictable synthons. Throughout this report we demonstrate the suitability of this synthetic strategy supported by six new SMOFs based on metal-nucleobase entities which fulfill the stated requirements: [Co(ThioG)3] (SMOF-4; ThioG = thioguaninato), [Co(Hade)2X2] (SMOF-5, SMOF-6; Hade = adenine and X = Cl–, Br–), [Cu8(μ3-OH)4(μ4-OH)4(ade)4(μ-ade)4(μ-Hade)2] (SMOF-7; ade = adeninato), [Cu4(μ3-ade)4(μ-ade)2(pentylNH2)2(CH3OH)2(CO3)2(H2O)2] (SMOF-8; pentylNH2 = 1-pentylamine), and [Cu2(μ-ade)2(ade)(μ-OH)(H2O)(CH3OH)]n (SMOF-9). SMOF-4 is built up from monomeric entities in which bidentate thioguaninat...

The present work summarizes the different approaches that can be applied to achieve porous materials based on metal–nucleobase systems. The rigidity and the multiple donor sites of the nucleobases make them suitable linkers to provide coordination bond sustained metal–organic frameworks (MOFs). Furthermore, the ability of the nucleobases to establish complementary hydrogen bonding interactions allows one to achieve similar metal–nucleobase porous materials but sustained by hydrogen bond pairing interactions between the nucleobases (supramolecular metal–organic frameworks, SMOFs).