Room temperature synthesis of a luminescent crystalline Cu-BTC coordination polymer and metal-organic framework

Coexistence of Redox-Active Metal and Ligand Sites in Copper-Based Two-Dimensional Conjugated Metal-Organic Frameworks as Active Materials for Battery-Supercapacitor Hybrid Systems

Two-dimensional (2D) conjugated metal-organic frameworks (c-MOFs) are promising materials for supercapacitor (SC) electrodes due to their high electrochemically accessible surface area coupled with superior electrical conductivity compared to traditional MOFs. In this work, porous and non-porous HHB-Cu (HHB=hexahydroxybenzene), derived through surfactant-assisted synthesis are studied as representative 2D c-MOF models with different characteristics, showing diverse reversible redox reactions with Na+ and Li+ in aqueous (10 M NaNO3) and organic (1.0 M LiPF6 in ethylene carbonate and dimethyl carbonate) electrolytes, respectively. These redox activities were here deployed to design negative electrodes for hybrid SCs (HSCs), combining the battery-like property of HHB-Cu at the negative electrode and the high capacitance and robust cyclic stability of activated carbon (AC) at the positive electrodes. In the organic electrolyte, porous HHB-Cu-based HSC achieves a maximum cell specific capacity (Cs) of 22.1 mAh g-1 at 0.1 A g-1, specific energy (Es) of 15.55 Wh kg-1 at specific power (Ps) of 70.49 W kg-1, and 77 % cyclic stability after 3000 gravimetric charge-discharge (GCD) cycles at 1 A g-1 (specific metrics calculated on the mass of both electrode materials). In the aqueous electrolyte, porous HHB-Cu-based HSC displays a Cs of 13.9 mAh g-1 at 0.1 A g-1, Es of 6.13 Wh kg-1 at 44.05 W kg-1, and 72.3 % Cs retention after 3000 GCD cycles. The non-porous sample, interesting for its superior electrical conductivity despite its limited surface area compared to its porous counterpart, shows lower Es performance but better rate capability compared to the porous one. This study indicates the potential of assembling a battery-SC hybrid system by rationally exploiting the battery-like behavior of 2D c-MOFs and the electrochemical double-layer capacitance of AC.

Bioinspired 1D Anisotropic Double-Spiral Metal Wires for Efficient Fog Harvesting

Innovative design strategies of fog harvesting devices (FHDs) demonstrate promising remedy for water crisis in arid areas. 1D FHDs ensure unimpeded wind circulation and can be manufactured more cost-effectively for extensive regions. Inspired by cactus thorns, desert beetles, and spider silk, two metal organic frameworks (MOFs) functionalized Cu wires with opposite wettability are double-twisted by a mechanical twisting machine, forming 1D double-spiral Cu wires with alternating superhydrophobic/superhydrophilic dual-MOF patterns. The biomimic integration design, namely conical microneedle, stripe-patterned contrasting wettability, and double-spiral geometry, allows for efficient fog water collection due to a collaborative process. Based on such multi-cooperation theory, the optimal fog collection efficiency of dual-MOF functionalized double-spiral Cu wires can reach 0.293 ± 0.013 g cm-2 min-1 by investigating the effect of the composition, the diameter ratio and twisting wavelength λ of the two constituent wires. The double-spiral metal wires with discrepant wettability not only propose a facile and cost-effective method for fog harvesting, but also share new physical insight to inspire novel design concepts for efficient fog collection devices, benefitting the fight against the global water crisis.

Exploring metal carbamates as precursors for the synthesis of metal-organic frameworks

In the synthesis of metal-organic frameworks (MOFs), the choice of the metal precursor plays a key role because of the influence that it can exert on the crystallization kinetics. The present work explores the use of metal-carbamato complexes for the synthesis of benchmark MOFs, namely HKUST-1 and UiO-66. Cu2(O2CNEt2)4·2NHEt2 and Zr(O2CNEt2)4, prepared using straightforward CO2 fixation reactions starting from the corresponding metal chlorides and diethylamine, were employed as metal precursors for MOF formation. The synthesis conditions, including the solvent, temperature, and ligand protonation degree, were systematically investigated, revealing metal carbamates as highly reactive precursors due to their prompt release of CO2 and amine upon reaction with protic species, i.e., the polycarboxylic linkers. This property of metal carbamates allowed us to identify room temperature protocols to achieve MOFs with comparable properties to those obtained using traditional metal precursors. Subsequent optimization of the reaction conditions led to the design of a one-pot synthetic strategy for HKUST-1, starting directly from copper(II) chloride and diethylamine under a CO2 atmosphere. The MOFs were characterized using various techniques, including powder X-ray diffraction, N2 sorption analysis, 1H nuclear magnetic resonance spectroscopy, and CHN elemental analysis, and compared to reference samples prepared according to literature procedures.

Highly efficient ultrasound-driven Cu-MOF/ZnWO4 heterostructure: An efficient visible-light photocatalyst with robust stability for complete degradation of tetracycline

Metal-organic frameworks (MOFs) are a significant class of porous, crystalline materials composed of metal ions (clusters) and organic ligands. The potential use of copper MOF (Cu-BTC) for the sonophotocatalytic degradation of Tetracycline (TC) antibiotic was investigated in this study. To enhance its catalytic efficiency, S-scheme heterojunction was created by combining Cu-BTC with Zinc tungstate (ZnWO4), employing an ultrasound-assisted hydrothermal method. The results demonstrated that the Cu-BTC/ZnWO4 heterojunction exhibited complete removal of TC within 60 min under simultaneous irradiation of visible light and ultrasound. Interestingly, the sonophotocatalytic degradation of TC using the Cu-BTC/ZnWO4 heterojunction showed superior efficiency (with a synergy index of ∼0.70) compared to individual sonocatalytic and photocatalytic degradation processes using the same heterojunction. This enhancement in sonophotocatalytic activity can be attributed to the formation of an S-scheme heterojunction between Cu-BTC and ZnWO4. Within this heterojunction, electrons migrated from Cu-BTC to ZnWO4, facilitated by the interface between the two materials. Under visible light irradiation, the built-in electric field, band edge bending, and coulomb interaction synergistically inhibited the recombination of electron-hole pairs. Consequently, the accumulated electrons in Cu-BTC and holes in ZnWO4 actively participated in the redox reactions, generating free radicals that effectively attacked the TC molecules. This study offers valuable perspectives on the application of a newly developed S-scheme heterojunction photocatalyst, demonstrating its effectiveness in efficiently eliminating diverse recalcitrant pollutants via sonophotocatalytic degradation.

Cu-HKUST-1 and Hydroxyapatite-The Interface of Two Worlds toward the Design of Functional Materials Dedicated to Bone Tissue Regeneration

A novel composite based on biocompatible hydroxyapatite (HA) nanoparticles and Cu-HKUST-1 (Cu-HKUST-1@HA) has been prepared following a layer-by-layer strategy. Cu-HKUST-1 was carefully selected from a group of four Cu-based metal-organic frameworks as the material with the most promising antimicrobial activity. The formation of a colloidal Cu-HKUST-1 layer on HA nanoparticles was confirmed by various techniques, e.g., infrared spectroscopy, powder X-ray diffraction, N2 sorption, transmission electron microscopy imaging, electron paramagnetic resonance, and X-ray absorption spectroscopy. Importantly, such a Cu-HKUST-1 layer significantly improved the nanomechanical properties of the composite, with Young's modulus equal to that of human cortical bone (13.76 GPa). At the same time, Cu-HKUST-1@HA has maintained the negative zeta potential (-16.3 mV in pH 7.4) and revealed biocompatibility toward human dermal fibroblasts up to a concentration of 1000 μg/mL, without inducing ex vivo hemolysis. Chemical stability studies of the composite over 21 days in a buffer-simulated physiological fluid allowed a detailed understanding of the transformations that the Cu-HKUST-1@HA undergoes over time. Finally, it has been confirmed that the Cu-HKUST-1 layer provides antibacterial properties to HA, and the synergism reached in this way makes it promising for bone tissue regeneration.