Unravelling co-catalyst integration methods in Ti-based metal-organic gels for photocatalytic H2 production.

The synthesis, characterization and photocatalytic hydrogen evolution reaction (HER) performance of a series of metal-organic gels (MOGs) constructed from titanium(IV)-oxo clusters and dicarboxylato linkers (benzene-1,4-dicarboxylato and 2-aminobenzene-1,4-dicarboxylato) are described. All the MOGs exhibit a microstructure comprised of metal-organic nanoparticles intertwined into a highly meso-/macroporous structure, as demonstrated by cryogenic transmission electron microscopy and gas adsorption isotherms. Comprehensive chemical characterization enabled the estimation of the complex formula for these defective materials, which exhibit low crystallinity and linker vacancies. To gain deeper insights into the local structure, X-ray absorption fine structure (XAFS) spectroscopy experiments were performed and compared to that of the analogous crystalline metal-organic framework. Additionally, the ultraviolet-visible absorption properties and optical band gaps were determined from diffuse reflectance spectroscopy data. The MOGs were studied as light absorbers for the sacrificial photocatalytic HER under simulated solar light irradiation using a platinum co-catalyst by either (1) in situ photodeposition or (2) ex situ doping process, through a post-synthetic metalation of the MOG structure. The chemical analysis of the metalation, along with high-angle annular dark-field scanning transmission electron microscopy, revealed that although the in situ addition of the co-catalyst led to greater HER rates (227 vs. 110 µmolH2 gMOG-1 h-1 for in situ and ex situ, respectively), the ex situ modification provided a finer distribution of platinum nanoparticles along the porous microstructure and, as a result, it led to a more efficient utilization of the co-catalyst (45 vs. 110 mmolH2 gPt-1 h-1).

Isoreticular Chemistry and Applications of Supramolecularly Assembled Copper-Adenine Porous Materials.

The useful concepts of reticular chemistry, rigid and predictable metal nodes together with strong and manageable covalent interactions between metal centers and organic linkers, have made the so-called metal-organic frameworks (MOFs) a flourishing area of enormous applicability. In this work, the extension of similar strategies to supramolecularly assembled metal-organic materials has allowed us to obtain a family of isoreticular compounds of the general formula [Cu7(µ-adeninato-κN3:κN9)6(µ3-OH)6(µ-OH2)6](OOC-R-COO)·nH2O (R: ethylene-, acetylene-, naphthalene-, or biphenyl-group) in which the rigid copper-adeninato entities and the organic dicarboxylate anions are held together not by covalent interactions but by a robust and flexible network of synergic hydrogen bonds and π-π stacking interactions based on well-known supramolecular synthons (SMOFs). All compounds are isoreticular, highly insoluble, and water-stable and show a porous crystalline structure with a pcu topology containing a two-dimensional (2D) network of channels, whose dimensions and degree of porosity of the supramolecular network are tailored by the length of the dicarboxylate anion. The partial loss of the crystallization water molecules upon removal from the mother liquor produces a shrinkage of the unit cell and porosity, which leads to a color change of the compounds (from blue to olive green) if complete dehydration is achieved by means of gentle heating or vacuuming. However, the supramolecular network of noncovalent interactions is robust and flexible enough to reverse to the expanded unit cell and color after exposure to a humid atmosphere. This humidity-driven breathing behavior has been used to design a sensor in which the electrical resistance varies reversibly with the degree of humidity, very similar to the water vapor adsorption isotherm of the SMOF. The in-solution adsorption properties were explored for the uptake and release of the widely employed 5-fluorouracil, 4-aminosalycilic acid, 5-aminosalycilic acid, and allopurinol drugs. In addition, cytotoxicity activity assays were completed for the pristine and 5-fluorouracil-loaded samples.

Thermochemical CO2 Reduction Catalyzed by Homometallic and Heterometallic Nanoparticles Generated from the Thermolysis of Supramolecularly Assembled Porous Metal-Adenine Precursors.

A family of unprecedented supramolecularly assembled porous metal-organic compounds (SMOFs), based on [Cu6M(µ-adeninato)6(µ3-OH)6(µ-H2O)6]2+ cations (MII: Cu, Co, Ni, and Zn) and different dicarboxylate anions (fumarate, benzoate, and naphthalene-2,6-dicarboxylate), have been employed as precursors of catalysts for the thermocatalytic reduction of CO2. The selected metal-organic cation allows us to tune the composition of the SMOFs and, therefore, the features and performance of the final homometallic and bimetallic catalysts. These catalysts were obtained by thermolysis at 600 °C under a N2 atmosphere and consist of big metal particles (10-20 µm) placed on the surface of the carbonaceous matrix and very tiny metal aggregates (<10 nm) within this carbonaceous matrix. The latter are the most active catalytic sites for the CO2 thermocatalytic reduction. The amount of this carbonaceous matrix correlates with the organic content present in the metal-organic precursor. In this sense, CO2 thermocatalytic reduction experiments performed over the homometallic, copper only, catalysts with different carbon contents indicate that above a certain value, the increase of the carbonaceous matrix reduces the overall performance by encapsulating the nanoparticles within this matrix and isolating them from interacting with CO2. In fact, the best performing homometallic catalyst is that obtained from the precursor containing a small fumarate counterion. On the other hand, the structural features of these precursors also provide a facile route to work with a solid solution of nanoparticles as many of these metal-organic compounds can replace up to 1/7 of the copper atoms by zinc, cobalt, or nickel. Among these heterometallic catalysts, the best performing one is that of copper and zinc, which provides the higher conversion and selectivity toward CO. XPS spectroscopy and EDX mappings of the latter catalyst clearly indicate the presence of Cu1-xZnx nanoparticles covered by small ZnO aggregates that provide a better CO2 adsorption and easier CO release sites.

Consecutive Single-Crystal-to-Single-Crystal Isomerization of Novel Octamolybdate Anions within a Microporous Hybrid Framework with Robust Water Sorption Properties.

The 3D hybrid framework [{Cu(cyclam)}3 (κ-Mo8 O27 )] ⋅ 14H2 O (1) (cyclam=1,4,8,11-tetraazacyclotetradecane) undergoes sequential single-crystal-to-single-crystal transformations upon heating to afford two different anhydrous phases (2 a and 3 a). These transitions modify the framework dimensionality and enable the isomerization of κ-octamolybdate (κ-Mo8 ) anions into λ (2 a) and µ (3 a) forms through metal migration. Hydration of 3 a involves condensation of one water molecule to the cluster to afford the γ-Mo8 isomer in 4, which dehydrates back into 3 a through the 6 a intermediate. In contrast, 2 a reversibly hydrates to form 5, exhibiting the same Mo8 cluster as that of 1. It is remarkable that three of the Mo8 clusters (κ, λ and µ) are new and that up to three different microporous phases can be isolated from 1 (2 a, 3 a, and 6 a). Water vapor sorption analyses show high recyclability and the highest uptake values for POM-based systems. The isotherms display an abrupt step at low humidity level desirable for humidity control devices or water harvesting in drylands.

Magnetic sustentation as an adsorption characterization technique for paramagnetic metal-organic frameworks.

Nowadays, there are many reliable characterization techniques for the study of adsorption properties in gas phase. However, the techniques available for the study of adsorption processes in solution, rely on indirect characterization techniques that measure the adsorbate concentration remaining in solution. In this work, we present a sensing method based on the magnetic properties of metal-organic frameworks (MOFs) containing paramagnetic metal centres, which stands out for the rapidity, low cost and in situ direct measurement of the incorporated adsorbate within the porous material. To illustrate this sensing technique, the adsorption in solution of four MOFs have been characterized: MIL-88A(Fe), MOF-74(Cu, Co) and ZIF-67(Co). Our simple and efficient method allows the direct determination of the adsorbed mass, as well as the measurement of adsorption isotherm curves, which we hope will greatly advance the study of adsorption processes in solution, since this method is independent of the chemical nature of the adsorbate that often makes its quantification difficult.

Multifunctional Lanthanide-Based Metal-Organic Frameworks Derived from 3-Amino-4-hydroxybenzoate: Single-Molecule Magnet Behavior, Luminescent Properties for Thermometry, and CO2 Adsorptive Capacity.

Herein, we describe and study a new family of isostructural multifunctional metal-organic frameworks (MOFs) with the formula {[Ln5L6(OH)3(DMF)3]·5H2O}n (where (H2L) is 3-amino-4-hydroxybenzoic acid ligand) for magnetism and photoluminescence. Interestingly, three of the materials (Dy-, Er-, and Yb-based MOFs) present single-molecule magnet (SMM) behavior derived from the magnetic anisotropy of the lanthanide ions as a consequence of the adequate electronic distribution of the coordination environment. Additionally, photoluminescence properties of the ligand in combination with Eu and Tb counterparts were studied, including the heterometallic Eu-Tb mixed MOF that shows potential as ratiometric luminescent thermometers. Finally, the porous nature of the framework allowed showing the CO2 sorption capacity.

Copper(II) invigorated EHU-30 for continuous electroreduction of CO2 into value-added chemicals.

The doping of zirconium based EHU-30 and EHU-30-NH2 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 CO2 electroreduction, while retained stable the performance during continuous transformation reaction.

The Chemistry of Zirconium/Carboxylate Clustering Process: Acidic Conditions to Promote Carboxylate-Unsaturated Octahedral Hexamers and Pentanuclear Species.

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 [Zr6(O)4(OH)4(OOC)12] secondary building unit found in many MOFs by removing carboxylic ligands in the case of the hexameric species ([Zr6(O)4(OH)4(OOC)8(H2O)8]4+) or by additionally removing one of the metal centers in the case of the pentameric entities ([Zr5(O)2(OH)6(OOC)4(H2O)11(alcohol)]6+). Going in detail, the unsaturated hexameric clusters exhibit different dispositions of their eight carboxylate ligands in such a way that the remaining four carboxylate-free positions are arranged according to a square planar or tetrahedral symmetry. It should be highlighted that the pentameric complexes imply an unprecedented core nuclearity in zirconium clusters and thus their isolation provides a novel building block for the design of metal-organic materials.

Innovative Microstructural Transformation upon CO2 Supercritical Conditions on Metal-Nucleobase Aerogel and Its Use as Effective Filler for HPLC Biomolecules Separation.

This work contributes to enlightening the opportunities of the anisotropic scheme of non-covalent interactions present in supramolecular materials. It provides a top-down approach based on their selective disruption that herein has been employed to process a conventional microcrystalline material to a nanofibrillar porous material. The developed bulk microcrystalline material contains uracil-1-propionic acid (UPrOH) nucleobase as a molecular recognition capable building block. Its crystal structure consists of discrete [Cu(UPrO)2 (4,4'-bipy)2 (H2 O)] (4,4'-bipy=4,4'-bipyridine) entities held together through a highly anisotropic scheme of non-covalent interactions in which strong hydrogen bonds involving coordinated water molecules provide 1D supramolecular chains interacting between them by weaker interactions. The sonication of this microcrystalline material and heating at 45 °C in acetic acid-methanol allows partial reversible solubilization/recrystallization processes that promote the cross-linking of particles into an interlocked platelet-like micro-particles metal-organic gel, but during CO2 supercritical drying, the microcrystalline particles undergo a complete morphological change towards highly anisotropic nanofibers. This unprecedented top-down microstructural conversion provides a nanofibrillar material bearing the same crystal structure but with a highly increased surface area. Its usefulness has been tested for HPLC separation purposes observing the expected nucleobase complementarity-based separation.

Single-Crystal-to-Single-Crystal Cluster Transformation in a Microporous Molybdoarsenate(V)-Metalorganic Framework.

The hybrid compound [Cu(cyclam)(H2O)2]0.5[{Cu(cyclam)}1.5{B-H2As2Mo6O26(H2O)}]·9H2O (1) (cyclam = 1,4,8,11-tetraazacyclotetradecane) was synthesized in aqueous solution by reacting the {Cu(cyclam)}2+ complex with a mixture of heptamolybdate and an arsenate(V) source. Crystal packing of 1 exhibits a supramolecular open-framework built of discrete covalent molybdoarsenate/metalorganic units and additional [Cu(cyclam)(H2O)2]2+ cations, the stacking of which generates squarelike channels parallel to the z axis with an approximate cross section of 10 × 11 Å2 where all the hydration water molecules are hosted. Thermal evacuation of solvent molecules yields a new anhydrous crystalline phase, but compound 1 does not preserve its single-crystalline nature upon heating. However, when crystals are dehydrated under vacuum, they undergo a structural transformation that proceeds via a single-crystal-to-single-crystal pathway, leading to the anhydrous phase [{Cu(cyclam)}2(A-H2As2Mo6O26)] (2). Total dehydration results in important modifications within the inorganic cluster skeleton which reveals an unprecedented solid-state B to A isomerization of the polyoxoanion. This transition also involves changes in the CuII bonding scheme that lead to covalent cluster/metalorganic layers by retaining the open-framework nature of 1. Compound 2 adsorbs ambient moisture upon air exposure, but it does not revert back to 1, and the hydrated phase [{Cu(cyclam)}2(A-H2As2Mo6O26)]·6H2O (2h) is obtained instead. Structural variations between 1 and 2 are reflected in electron paramagnetic resonance spectroscopy measurements, and the permanent microporosity of 2 provides interesting functionalities to the system such as the selective adsorption of gaseous CO2 over N2.

Porous TiO2 thin film-based photocatalytic windows for an enhanced operation of optofluidic microreactors in CO2 conversion.

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.

Macroscopic Ultralight Aerogel Monoliths of Imine-based Covalent Organic Frameworks.

The use of covalent organic frameworks (COFs) in practical applications demands shaping them into macroscopic objects, which remains challenging. Herein, we report a simple three-step method to produce COF aerogels, based on sol-gel transition, solvent-exchange, and supercritical CO2 drying, in which 2D imine-based COF sheets link together to form hierarchical porous structures. The resultant COF aerogel monoliths have extremely low densities (ca. 0.02 g cm-3 ), high porosity (total porosity values of ca. 99 %), and mechanically behave as elastic materials under a moderate strain (<25-35 %) but become plastic under greater strain. Moreover, these COF aerogels maintain the micro- and meso-porosity of their constituent COFs, and show excellent absorption capacity (e.g. toluene uptake: 32 g g-1 ), with high removal efficiency (ca. 99 %). The same three-step method can be used to create functional composites of these COF aerogels with nanomaterials.

Crystal structure, magneto-structural correlation, thermal and electrical studies of an imidazolium halometallate molten salt: (trimim)[FeCl4].

A novel imidazolium halometallate molten salt with formula (trimim)[FeCl4] (trimim: 1,2,3-trimethylimidazolium) was synthetized and studied with structural and physico-chemical characterization. Variable-temperature synchrotron X-ray powder diffraction (SXPD) from 100 to 400 K revealed two structural transitions at 200 and 300 K. Three different crystal structures were determined combining single crystal X-ray diffraction (SCXD), neutron powder diffraction (NPD), and SXPD. From 100 to 200 K, the compound exhibits a monoclinic crystal structure with space group P21/c. At 200 K, the former crystal system and space group are retained, but a disorder in the organic cations is introduced. Above 300 K, the structure transits to the orthorhombic space group Pbcn, retaining the crystallinity up to 400 K. The study of the thermal expansion process in this temperature range showed anisotropically evolving cell parameters with an axial negative thermal expansion. Such an induction occurs immediately after the crystal phase transition due to the translational and reorientational dynamic displacements of the imidazolium cation within the crystal building. Electrochemical impedance spectroscopy (EIS) demonstrated that this motion implies a high and stable solid-state ionic conduction (range from 4 × 10-6 S cm-1 at room temperature to 5.5 × 10-5 S cm-1 at 400 K). In addition, magnetization and heat capacity measurements proved the presence of a three-dimensional antiferromagnetic ordering below 3 K. The magnetic structure, determined by neutron powder diffraction, corresponds to ferromagnetic chains along the a-axis, which are antiferromagnetically coupled to the nearest neighboring chains through an intricate network of superexchange pathways, in agreement with the magnetometry measurements.

Correction: Crystal structure, magneto-structural correlation, thermal and electrical studies of an imidazolium halometallate molten salt: (trimim)[FeCl4].

[This corrects the article DOI: 10.1039/D0RA00245C.].

Adenine nucleobase directed supramolecular architectures based on ferrimagnetic heptanuclear copper(II) entities and benzenecarboxylate anions.

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.

[Zr6O4(OH)4(benzene-1,4-dicarboxylato)6]n: a hexagonal polymorph of UiO-66.

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.

Magnetic Structure, Single-Crystal to Single-Crystal Transition, and Thermal Expansion Study of the (Edimim)[FeCl4] Halometalate Compound.

This contribution addresses standing questions about the nature and consequences of the ion self-assembly and magnetic structures, as well as the molecular motion of the crystalline structure as a function of the temperature, in halometalate materials based on imidazolium cation. We present the magnetic structure and magnetostructural correlations of 1-ethyl-2,3-dimethylimidazolium tetrachloridoferrate, (Edimim)[FeCl4], resolved by neutron diffraction studies. Single-crystal, synchrotron powder X-ray diffraction and powder neutron diffraction techniques have been combined to follow the temperature evolution on its crystallographic structure from 2 K close to its melting point (340 K). In this sense, slightly above room temperature (307 K) (Edimim)[FeCl4] presents a single-crystal to single-crystal transition (SCSC), from phase I (space group P21/n) to phase II (P21/m), accompanied by a notable increase in the disorder of the imidazolium cation, as well as in the metal complex anion. The temperature evolution and solid-phase transitions of the presented compound were followed in detail by synchrotron X-ray powder diffraction (SXPD), which confirms the occurrence of another phase transition at 330 K, phase III (P21/m), the crystal structure of which was elucidated from the SXPD pattern. Moreover, this material presents an anisotropic thermal expansion with a switch from axial positive to negative thermal expansion coefficients as the temperature is raised above the first phase transition, which has been correlated with the molecular motion of the imidazolium-based molecules, producing not only a shortening of the counterion···counterion distances but also the occurrence of different quasi-isoenergetic crystal structures as a function of the temperature.

Synthesis of heterometallic metal-organic frameworks and their performance as electrocatalyst for CO2 reduction.

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.

Thermally-Triggered Crystal Dynamics and Permanent Porosity in the First Heptatungstate-Metalorganic Three-Dimensional Hybrid Framework.

The hybrid compound [{Cu(cyclam)}3 (W7 O24 )]⋅15.5 H2 O (1) (cyclam=1,4,8,11-tetraaza-cyclotetradecane) was synthesized by reacting the {Cu(cyclam)}2+ complex with a tungstate source in water at pH 8. Compound 1 exhibits an unprecedented three-dimensional covalent structure built of heptatungstate clusters linked through metalorganic complexes in a POMOF-like framework that displays water-filled channels. This dynamic architecture undergoes two sequential single-crystal-to-single-crystal transformations upon thermal evacuation of water molecules to result in the partially dehydrated [{Cu(cyclam)}3 (W7 O24 )]⋅12 H2 O (2) and anhydrous [Cu(cyclam)]0.5 [{Cu(cyclam)}2.5 (W7 O24 )] (3) crystalline phases. These transitions are associated with cluster rotations and modifications in the CuII coordination geometries, which reduce the dimensionality of the original lattice to layered systems but preserving the porous nature. Phase 3 reverts to 2 upon exposure to ambient moisture, whereas the transition between 1 and 2 proved to be irreversible. The permanent microporosity of 3 was confirmed by gas sorption measurements (N2 , CO2 ), which reveal a system of parallel channels made of wide cavities connected through narrow necks that limit the adsorption process. This observation is in good agreement with Grand Canonical Monte Carlo simulations.

Copper-Based Metal-Organic Porous Materials for CO2 Electrocatalytic Reduction to Alcohols.

The electrocatalytic reduction of CO2 has been investigated using four Cu-based metal-organic porous materials supported on gas diffusion electrodes, namely, (1) HKUST-1 metal-organic framework (MOF), [Cu3 (µ6 -C9 H3 O6 )2 ]n ; (2) CuAdeAce MOF, [Cu3 (µ3 -C5 H4 N5 )2 ]n ; (3) CuDTA mesoporous metal-organic aerogel (MOA), [Cu(µ-C2 H2 N2 S2 )]n ; and (4) CuZnDTA MOA, [Cu0.6 Zn0.4 (µ-C2 H2 N2 S2 )]n . The electrodes show relatively high surface areas, accessibilities, and exposure of the Cu catalytic centers as well as favorable electrocatalytic CO2 reduction performance, that is, they have a high efficiency for the production of methanol and ethanol in the liquid phase. The maximum cumulative Faradaic efficiencies for CO2 conversion at HKUST-1-, CuAdeAce-, CuDTA-, and CuZnDTA-based electrodes are 15.9, 1.2, 6, and 9.9 %, respectively, at a current density of 10 mA cm-2 , an electrolyte-flow/area ratio of 3 mL min cm-2 , and a gas-flow/area ratio of 20 mL min cm-2 . We can correlate these observations with the structural features of the electrodes. Furthermore, HKUST-1- and CuZnDTA-based electrodes show stable electrocatalytic performance for 17 and 12 h, respectively.