Porous HKUST-1 Research Articles

Eco-friendly and cost-effective synthesis of hierarchical porous HKUST-1 from thin waste electric cables for enhanced cationic dye removal

HKUST-1, as a type of metal-organic framework (MOF), has attracted significant interest for various applications. However, its use for adsorption applications is hindered by its microporous structure, which negatively impacts the diffusion and mass transfer of large particles (> 2 nm). Concurrently, waste electric cables from discarded vehicles and electronic equipment pose significant environmental challenges. To address these issues, we developed a novel recycling method using copper hydroxide recovered from waste-thin electric cables as the metal source for synthesizing hierarchical porous HKUST-1 (W) using a green approach at a low temperature. The resulting HKUST-1 (W) exhibited interesting properties compared to the typical HKUST-1 (C) synthesized from commercial precursors, showing a microporous-mesoporous structure with enhanced molecular mass transport, while HKUST-1 (C) exhibited only micropores. Moreover, the waste-derived HKUST-1 (W) formed interconnected small particles with enhanced methylene blue (MB) removal properties compared to HKUST-1 (C), mainly due to its hierarchical porous structure facilitating easy mass transfer of MB. To evaluate the industrial potential of our adsorbent, we conducted a fixed-bed adsorption column (FBAC) experiment, which showed that HKUST-1 (W) achieved a high removal efficiency of 99 %, confirming its effectiveness as a dye adsorbent in both batch experiments and a FBAC. This approach opens new perspectives in applying upcycled waste-based materials in synthesizing hierarchical porous MOFs.

Construction of the Z-Scheme Heterogeneous HKUST-1/BiVO4 Nanorod Composite for Enhanced Piezo-Photocatalytic Reduction Performance of Cr(VI).

In recent years, piezo-photocatalysis has become a promising strategy for solving environmental pollution problems by adding additional mechanical energy to the photocatalysis process. This work reported the effective synthesis of a variety of HKUST-1/BiVO4 heterogeneous materials by combining monoclinic BiVO4 and porous HKUST-1 semiconductors. The piezo-photocatalytic properties of HKUST-1/BiVO4 were studied by the reduction of hexavalent chromium (Cr(VI)) under visible-light irradiation and ultrasonic waves. In the piezo-photocatalysis process, the best reduction rates among as-prepared HKUST-1/BiVO4 composites were up to 96.20% of 10 ppm Cr(VI) solution, which was approximately 1.80 times that under visible light and about 4.13 times that under ultrasound. Under the action of the piezoelectric potential, the availability of free radicals increased the reduction rate of Cr(VI) and reached a synergistic effect of 1.14-fold.

Spray synthesis of hierarchical porous metal-organic framework HKUST-1 with soft templates and methylene blue adsorption performance

We synthesize hierarchical porous HKUST-1 (HP-HKUST-1) with micropores, mesopores, and macropores using the spray synthesis and soft template methods. We utilize two types of structure-directing agents (SDAs), namely cetyltrimethylammonium bromide and citric acid for C-HKUST-1 and triblock copolymer P123 for P-HKUST-1. Paq-HKUST-1 is successfully synthesized using only water as the solvent. The volumes of the mesopores and macropores are changed by the amounts of SDAs. The highest values are: 0.78 and 0.30 cm3/g for C-HKUST-1; 0.44 and 0.38 cm3/g for P-HKUST-1; and 0.30 and 0.23 cm3/g for Paq-HKUST-1, respectively. HP-HKUST-1 shows high methylene blue (MB) adsorption rates and capacities of over 700 mg/g owing to its HP structure. In particular, C-HKUST-1 exhibits a rate constant of 19.7 mg/mg min for MB adsorption based on the pseudo-second-order adsorption kinetic model. This rate constant is 10 times higher than that of batch-synthesized HKUST-1. Furthermore, HP-HKUST-1 exhibits good stability for reuse as an MB adsorbent.

Construction of S-scheme heterogeneous HKUST-1/g-C3N4 with the piezoelectric effect for enhanced piezo-photocatalytic performance

In recent years, using external mechanical energy to solve environmental pollution problems has gradually become a promising strategy, such as piezoelectric catalysis and piezoelectric photocatalysis. In this paper, a series of HKUST-1/g-C3N4 composite materials were successfully synthesized by the combination of g-C3N4 with S-vacancy and porous HKUST-1 semiconductor. Under visible light irradiation and ultrasonic action, the catalytic activity of HKUST-1/g-C3N4 on RhB degradation was investigated. When the mass ratio of HKUST-1 to g-C3N4 is 1:0.3 during the process of piezoelectric photocatalysis, the as-prepared HKUST-1/g-C3N4 composite had the best RhB degradation performance up to 94.42%, which is about 2.83 times that of visible light and 3.56 times that of ultrasonic waves. According to the result of the trapping experiment, the process of piezo-photocatalytic reaction could produce the number of reactive oxygen species (ROS), and the hydroxyl radical (•OH) was crucial in the breakdown of pollutants.

Encapsulation of Imazalil in HKUST-1 with Versatile Antimicrobial Activity.

Based on high surface areas, adjustable porosity and microbicide activity, metal-organic frameworks (MOFs) HKUST-1 are widely used as drug release carriers for their slow degradation characteristics under slightly acidic conditions. In this work, porous HKUST-1 was reacted rapidly by cholinium salt (as the deprotonation agent and template) in an aqueous solution at room temperature. A novel antimicrobial system based on an imazalil encapsulated metal organic framework (imazalil IL-3@HKUST-1) was established. Imazalil IL-3@HKUST-1 could achieve synergism in inhibiting pathogenic fungi and bacteria. Moreover, six days after treatment, the slow and constant release of imazalil from imazalil IL@HKUST-1 exhibited better sustainability and microbicidal activity than imazalil. We believe that the method may provide a new strategy for related plant diseases caused by bacteria or fungi.

(Digital Presentation)Cu Coordination Environment Modification Via Atomic Layer Infiltration As High Selective CO2RR Catalyst

Carbon dioxide (CO2) is the most notorious greenhouse gas, released by both natural and artificial processes. In an ideal scenario, the production and consumption of CO2 should be balanced so that the concentration of CO2 in atmosphere remains constant to maintain environmental stability. Unfortunately, with the intensification of human industrial activities, this balance has gradually been disrupted, leading to more CO2 production and making global warming a pressing issue. With carbon neutrality gaining increasing attention, electrochemical CO2 reduction reaction (CO2RR) has emerged as a research orientation which converts CO2 to value-added products while storing renewable energy. Cu-based electrocatalysts have been studied extensively for the CO2RR into hydrocarbons in aqueous solutions under environmental conditions. However, they frequently endure low Faradaic Efficiency (FE) and selectivity of specific single product. Particularly, precise construction of Cu micro-environment is of great challenge for the design and fabrication of excellent Cu-based CO2RR catalysts.Atomic layer infiltration (ALI) allows gas phase precursors to penetrate and diffuse into porous substrates through their nanoporous structures and to grow within the subsurface. Aiming at systematically regulating the Cu metal site micro-environment, porous HKUST-1 containing paddle-wheel Cu coordination nodes was chosen as a template and modified with ALI technique in this work. Various metals were introduced into HKUST-1 using ALI method to construct bimetallic sites which tended to produce CO, HCOOH and other products with high FEs. Density Functional Theory (DFT) calculations prove the modification with metals by ALI enhances the adsorption enthalpy of CO2 and alters the bonding interaction between reaction intermediates and adsorption center, thereby changing the reaction pathways. MOF conversion technique based on atomic layer deposition (ALD) will be utilized to fabricate HKUST-1 thin film in our future work, which allows nanometer precision of catalyst loading to balance active-site density with mass/charge transfer. The proposed ALI and ALD techniques elucidate the reliance of CO2RR selectivity on the Cu micro-environment and provide a platform for regulating Cu or other metal-base electrocatalyst coordination environment to facilitate high selectivity of CO2RR in the future

Membrane adsorber with hierarchically porous HKUST-1 immobilized in membrane pores by flowing synthesis

A membrane adsorber with hierarchically porous HKUST-1 (HP-HKUST-1) immobilized in membrane pores has been fabricated by flowing synthesis. The X-ray diffraction (XRD) characteristics indicate that the structural integrity of the HP-HKUST-1 immobilized in the membrane pores can be kept after template agents are removed. Other characteristics prove the effective immobilization of HP-HKUST-1 in membrane pores. As a concept-of-proof, the adsorption for Congo red (CR) and Methylene blue (MB) is carried out to evaluate the adsorption performance of the membrane adsorber. The adsorption capacity for CR with 458 mg g-1 and MB with 241 mg g-1 can be obtained by HP-HKUST-1 powder, which is 2–3 times higher than those by HKUST-1 powder, owing to the mesopores with rich active adsorption sites. When the solution flows through the membrane adsorber, the adsorption rate for these adsorbates in the range of 0.049 g mg-1 h-1 and 0.129 g mg-1 h-1 can be obtained, which is 4–5 times higher than that by HP-HKUST-1 powder, owing to the enhanced mass transfer in the confined space of the membrane pores with micro or nano scale. After going through seven adsorption-desorption experiments, the membrane adsorber with HP-HKUST-1 immobilized shows remarkable repeatability.

Hierarchical porous HKUST-1 fabricated by microwave-assisted synthesis with CTAB for enhanced adsorptive removal of benzothiophene from fuel

• Hierarchical porous defective HKUST-1 rapidly obtained by microwave-assisted method. • Enhanced benzothiophene removal from fuel by defective HKUST-1 over HKUST-1. • Defective HKUST-1 exposes more active sites and facilitates adsorbates diffusion. • CTAB-H-0.5 shows excellent adsorption and regeneration performance for BT removal. Ultra-deep removal of thiophene sulfides from transportation fuel via adsorption has aroused great attention under the pressure of gradually demanding environmental regulations. The development of high-efficiency adsorbents is the key to adsorptive desulfurization for producing clean transportation fuels. In this work, a microwave-assisted synthesis method was applied to rapidly fabricate hierarchical porous defective HKUST-1 (DEHKUST-1) towards removing benzothiophene from model fuel by selective adsorption. The effects of cetyltrimethylammonium bromide (CTAB) dosage, adsorption temperature and adsorption contact time on the DEHKUST-1 desulfurization performance were systematically investigated. The characterization results proved that both metal clusters and linker defects were generated in the as-prepared DEHKUST-1. CTAB as template could modulate the pore distribution and introduce reasonable defects in the framework of HKUST-1. At CTAB: Cu 2+ = 0.5 by mole ratio, a regular mesoporous distribution of 25–30 nm could be obtained with DEHKUST-1; it exhibited an impressive enhancement in adsorptive desulphurization performance. The maximum adsorption capacity of the adsorbent attained 14.4 mg S/g adsorbent at 20 °C in 4 h. Even after CTAB-H-0.5 was regenerated six times, its adsorption capacity remained 93% as that of the as-prepared adsorbent. An adsorption mechanism was proposed to illustrate the promoting desulfurization performance by introduction of hierarchical porous in HKUST-1. By virtue of the rapid synthesis and remarkable benzothiophene removal capacity, the DEHKUST-1 could be a potential adsorbent in desulfurization from real fuels.

Synthesis of composite material HKUST-1/LiCl with high water uptake for water extraction from atmospheric air

As the global water shortage problems become more serious, vigorously developing water extraction from atmospheric air is significant and broad prospects. In order to improve water vapor uptake, a new type of composite material was fabricated by impregnating porous HKUST-1 with the aqueous solution of hygroscopic salt LiCl. The effect of impregnation salt concentration on hygroscopicity of HKUST-1/LiCl was discussed. The crystalline phase and morphology of the composites were characterized by Scanning Electron Microscopy and X-ray diffraction. The experimental results indicated that the composites obtained by dipping HKUST-1 with the solution of 20% LiCl, exhibiting excellent adsorption capacities and fast adsorption rates. Its amount adsorbed at 25 ℃ and 50% RH reached 1.09 g/g, which were much higher than the pristine HKUST-1. Additionally, the composite material with a high water uptakes at low relative humidity (25 ℃, 30% RH, 0.50 g/g) suggested that the compositehad excellent adsorption properties. All the results indicated that the novel composite materialHKUST-1/LiCl are expected to be a promising candidate for water generation from atmospheric air by natural sunlight.

Structuring Metal-Organic Framework Materials into Hierarchically Porous Composites through One-Pot Fabrication Strategy.

Controlled synthesis of metal-organic framework (MOF)-based materials with multiple levels of porous structures across different length scales is of great interest in various applications but it still remains challenging. Most of the current strategies are time consuming and labor intensive, and not readily scaled-up. In this work, we introduce a straightforward one-pot fabrication strategy to prepare a robust and flexible hierarchically macro-meso-micro porous HKUST-1/polyvinylidene fluoride (PVDF) composite through solvent evaporation, in which MOF crystallization and polymer precipitation are combined together. The effect of the MOF precursor and the polymer initial amount on the morphology of the final composite was thoroughly studied. The interaction between the MOF and the polymer during the evaporation process is the key factor, which would limit the mobility of the polymer chains and cause instability in the MOF growth, thus endowing the composite with a hierarchically macro-meso-micro porous structure. This "all-in-one" porous structure could enhance the mass transport property of molecules within the composite. The obtained HKUST-1/PVDF composite showed an enhanced CO2 adsorption rate constant of 0.821 min-1 (298 K, 1 bar), which was 3.5 times higher than that of the pristine MOF. In addition, the composite showed an equivalent gas adsorption capacity under all tested pressures and greatly improved water stability.

Acetic acid as a solvent for the synthesis of metal–organic frameworks based on trimesic acid

Nowadays, there is a great interest in the design of new metal–organic frameworks (MOFs) synthetized by routes that can be transferred to industrial scale with low environmental impact. In this context, this work explores the use of a soft method for the synthesis of MOFs, in which neat acetic acid is used as the reaction media. Trimesic acid (H3BTC) was chosen as the organic linker source and combined with different metal acetates, all these precursor being moderately soluble in hot acetic acid. The metal acetate provides both the metallic cation and a base, the acetate, necessary to deprotonate the H3BTC. Three first row transition metals, Cu, Co and Ni, and one heavy metal, Bi, were chosen for the study. Results denoted that the metal acetate was determinant to direct the nature of the precipitated material. For instance, the precipitation of the well-known porous HKUST-1 was observed from Cu acetate and H3BTC in neat acetic acid, giving systems with hierarchical porosity. Contrarily, for Co and Bi the use of acetic acid as a solvent yielded two 2D non porous coordination polymers, [Co6(BTC)2(Ac)6(HAc)3] (1) and [Bi(HBTC)(Ac)] (3), respectively. These new compounds were structurally elucidated. Moreover, the magnetic behaviour was analysed for the Co compound (1). Finally, an amorphous phase was precipitated for Ni. In the latter case, the use of propionic acid, with a higher boiling point than acetic acid, led to the precipitation of a crystalline material.

A polydopamine-modified reduced graphene oxide (RGO)/MOFs nanocomposite with fast rejection capacity for organic dye

A nanocomposite of metal-organic frameworks (MOFs)-HKUST-1 based on graphene oxide (GO) was modified by polydopamine (PDA). These nanomaterials formed the PDA/RGO/HKUST-1 membrane over the surface of the commercial cellulose acetate membrane support layer to treat dye wastewater. The membranes were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results showed enhanced membrane separation performance because of improved surface flatness and layer spacing. With the insertion of porous HKUST-1 and the cross-linking modification of PDA, the PDA/RGO/HKUST-1 membranes exhibited excellent flux, rejection, hydrophilic, and anti-fouling performance. The composite membrane could effectively reject methylene blue and Congo red, with removal rates of 99.8% and 89.2%, respectively. In addition, the flux of the PDA/RGO/HKUST-1 membrane increased 31-fold with the addition of HKUST-1 and PDA. Overall, the prepared high-flux composite membrane can be used as an excellent material in a variety of environmental applications.

Optimized synthesis of nano-scale high quality HKUST-1 under mild conditions and its application in CO2 capture

This study was focused on the development of an optimized method for the rapid synthesis of nano-scale HKUST-1 with high yield, high surface area and high CO2 uptake capacity but under mild conditions. A series of HKUST-1 were synthesized under different conditions, such as preparation time, temperature, activation method, etc. It was found that the nano-scale HKUST-1 MOFs (T85-3-Pm4-120) was successfully synthesized at a high yield (87%) under low temperature (85 °C) using a mixture of Triethylamine (TEA), Cu2+ and trimesic acid (TMA) with a molar ratio of 6:3:2. The highest porosity was achieved via this pristine HKUST-1 being activated (powder activation, drying at 120 °C) four times using methanol to remove impurities trapped in the pores. The best HKUST-1 MOFs (T85-3-Pm4-120) hereby prepared was then tested in CO2 adsorption and exhibited an adsorption capacity of 2.5 mmol/g. It is therefore demonstrated that the new approach proposed in this study is a rapid and effective way to synthesize highly porous HKUST-1 MOFs under mild conditions, which is of comparable surface area and CO2 uptake capacity with those MOFs prepared under harsh conditions.

Porous HKUST-1 derived CuO/Cu2O shell wrapped Cu(OH)2 derived CuO/Cu2O core nanowire arrays for electrochemical nonenzymatic glucose sensors with ultrahigh sensitivity

Self-supported CuO/Cu2O@CuO/Cu2O core–shell nanowire arrays (NWAs) are successfully fabricated by a simple and efficient method in this paper. Anodized Cu(OH)2 NWAs could in-situ convert to HKUST-1 at room temperature easily. Cu(OH)2 NWAs cores and HKUST-1 shells transform into CuO/Cu2O simultaneously after calcinations and form CuO/Cu2O@CuO/Cu2O core–shell NWAs. This smart configuration of the core–shell structure not only avoids the agglomeration of the traditional MOF-derived materials in particle-shape, but also facilitates the ion diffusion and increases the active sites. This novel structure is employed as substrate to construct nonenzymatic glucose sensors. The results indicate that glucose sensor based on CuO/Cu2O@CuO/Cu2O core–shell NWAs presents ultrahigh sensitivity (10,090 μA mM−1 cm−2), low detection limit (0.48 μM) and wide linear range (0.99–1,330 μM). In addition, it also shows excellent anti-interference ability toward uric acid, ascorbic acid and L-Cysteine co-existing with glucose, good reproducibility and superior ability of real sample analysis.

Hierarchically porous metal-organic frameworks: rapid synthesis and enhanced gas storage.

Large pore sizes, high pore volumes, facile synthesis conditions, and high space-time yields are recognized as four crucial criteria in the fabrication of metal-organic frameworks (MOFs). However, these four objectives are rarely realized together. Herein, we have developed a simple and versatile method that employs 1,4-butanediamine (BTDM) as a template for rapidly fabricating four stable hierarchically porous MOFs (H-MOFs), including HKUST-1, ZIF-8, ZIF-67, and ZIF-90. The synthesis conditions are simple and facile at room temperature and ambient pressure, and the synthesis time can be shortened to 1 min. The resultant H-MOFs exhibit multimodal hierarchically porous structures with meso- and macropores interconnected with micropores, as well as high pore volumes (0.76 cm3 g-1). The maximum space-time yield for the hierarchically porous HKUST-1 reaches 7.4 × 104 kg m-3 d-1, at least one order of magnitude higher than previous reported yields. Notably, the additive BTDM not only facilitates crystal growth but also guides the formation of meso- and macropores. The synthesis route is highly versatile, as analogues (e.g., tetramethyl-1,3-diaminopropane and tetramethyldiaminomethane) can also be employed as templates to prepare diverse H-MOFs. Furthermore, the porosities of the H-MOFs are readily tuned by controlling the metal source, template amount and type of template. The as-synthesized H-MOFs act as adsorbents with significantly improved performances relative to those of microporous MOFs used for CH4 and CO2 gas storage. This strategy may aid in the large-scale industrial synthesis of desirable H-MOFs for gas storage.

Metal ion induced porous HKUST-1 nano/microcrystals with controllable morphology and size

Porous coordination polymer HKUST-1 [Cu3(BTC)2] (H3BTC = 1,3,5-benzenetricarbocylic acid) nano/microcrystals have been fabricated by an environment friendly facile direct precipitation method at room temperature using inorganic salts such as NaNO3, NaCl, NaBr, KNO3, KCl and KBr as additives. It is found that the concentration of the inorganic salt has an important impact on the morphology and size of the HKUST-1 crystals, and their morphology changed from cube to cuboctahedron and finally to octahedron by increasing the concentration of inorganic salts. Gas adsorption measurements reveal that HKUST-1 nano/microcrystals with different morphologies show high specific surface areas, and their gas sorption properties depend on the crystal morphology and size.

One-pot synthesis of a hierarchical microporous-mesoporous phosphotungstic acid-HKUST-1 catalyst and its application in the selective oxidation of cyclopentene to glutaraldehyde

A hierarchical microporous-mesoporous metal-organic framework of HKUST-1(Cu)-encapsulated phosphotungstic acid (HPW) material, referred to as HPWs@Meso-HKUST-1, is prepared by a one-pot synthesis method using cetyltrimethylammonium bromide as the supramolecular template. The addition of HPWs to the synthesis mixture of hierarchical porous HKUST-1 results in the direct encapsulation of HPWs inside the mesopores of the HKUST-1 structure, with a homogeneous distribution over the HKUST-1 crystals, which is confirmed by XRD, FT-IR, N2 adsorption, UV-Vis DRS, and TEM. FT-IR-CO adsorption experiments indicated that additional Lewis acid sites were present in the HPWs@Meso-HKUST-1 sample. The novel heterogeneous catalyst demonstrates excellent catalytic performance for the selective oxidation of cyclopentene (CPE) to glutaraldehyde (GA) using tert-butyl hydroperoxide and acetonitrile (MeCN) as the oxidant and solvent, respectively. The high activity of the catalyst is attributed to the mesostructure of the catalyst and the nature and appropriate abundance of the HPWs—being highly dispersed with the addition of Lewis sites. After a reaction for 36 h, the 30% wt% HPWs@Meso-HKUST-1 catalyst exhibits a CPE conversion of 92.5% and a high GA yield of 73%. Furthermore, the HPWs@Meso-HKUST-1 material is sufficiently stable to prevent the leaching of HPWs, and behaves as a true heterogeneous catalyst that can be repeatedly recycled without sustaining a loss of activity and selectivity in the selective oxidation of CPE.

Synthesis and characterization of porous HKUST-1 metal organic frameworks for hydrogen storage

Hydrogen storage capacity has been investigated on a copper-based metal organic framework named HKUST-1 with fine structural analyses. The crystalline structure of HKUST-1 MOF has been confirmed from the powder X-ray diffraction and the average particle diameter has been found about 15–20 μm identified by FE-SEM. Nitrogen adsorption isotherms show that HKUST-1 MOF has approximately type-I isotherm with a BET specific surface area of 1055 m2g−1. Hydrogen adsorption study shows that this material can store 0.47 wt.% of H2 at 303 K and 35 bar. The existence of Cu (II) in crystalline framework of HKUST-1 MOF has been confirmed by pre-edge XANES spectra. The sharp feature at 8985.8 eV in XANES spectra represents the dipole-allowed electron transition from 1s to 4pxy. In addition, EXAFS spectra indicate that HKUST-1 MOF structure has the Cu–O bond distance of 1.95 Å with a coordination number of 4.2.