MIL-53金屬-有機架構物之特性鑑定及儲氫機制之研究

Recently, titanium dioxide has been recognized as an excellent photocatalyst material applied on many field especially for environmental science or engineering. Titanium dioxide nanotubes (TDNs)/titanate nanotubes (TNTs) with high specific surface area have been also studied due to its excellent catalytic activities, long-term stability, non-toxicity, and low cost. Therefore, the main objectives of the present study were to prepare TDNs/TNTs in large quantities by hydrothermal routes and to characterize the photocatalytic properties, fine structures, formation mechanism, adsorption abilities of TDNs or removal efficiency of dye pollutants in wastewaters by TDNs/TNTs. In addition, via Langmuir-Hinshelwood model and pseudo-second-order equation determining the photocatalytic kinetic parameter and adsorption kinetic parameter was also investigated. Experimentally, anatase TiO2 nanoparticle was used as a precursor for TDNs/TNTs synthesis. The TNTs characterized by FE-SEM and TEM microphotos were fabricated in different reaction temperatures of 110 ~ 270 ℃. The results showed that the length and diameter of TNTs ranged of 50 ~ 100 nm and 10 ~ 15 nm, respectively. The XRPD patterns showed that TNTs are sodium/hydrogen titanate structures (e.g. (H,Na)2Ti3O7 xH2O). The EDX data indicated that TNTs consist of Ti, O, and Na atoms. In addition, the results showed that the length and diameter of TDNs ranged of 50 ~ 100 nm and 10 ~ 15 nm, respectively. The XRPD patterns showed TDNs are anatase-typed and titanate structures. The EDX data indicated that TDNs were composed of Ti and O atoms. The BET surface area (pore volume) of TDNs and TNTs are 292 m2/g (1.02 cm3/g) and 277 m2/g (1.145 cm3/g), respectively. X-ray absorption near edge structure (XANES) or extended X-ray absorption fine structure (EXAFS) spectroscopy was performed to identify the oxidative station and fine structures of TDNs and TNTs. By using XANES spectra, the valency and framework of TDNs (TNTs) are Ti(IV) with octahedral (similar anatase) structures. The EXAFS data revealed that TDNs (TNTs) have a first shell of Ti-O bonding with bond distances of 1.95 A (1.94 A) and coordination numbers were 2 (2). Furthermore, investigation of the formation mechanism of these TDNs/TNTs was also conducted. The results revealed that the TiO2 anatase nanoparticles can be solved into layer under strong alkaline. The layer may further curl itself to reduce the energetics and form these TDNs/TNTs. FTIR and ESCA spectra showed that the existence of moisture with H-O-H, Ti-O or Ti-O-H bonding on the surface of TDNs. The UV/Vis spectra revealed that the critical wavelength of TDNs and TNTs are 385 nm and 378 nm, respectively. RAMAN spectra showed that form of TNTs (TDNs) consist of titanate structure and anatase structure (titanate structure). The TGA curves of TDNs oxidation showed that the tubular structures transform to particle nanophases ranged of 400 ~ 600℃. The adsorption mechanisms of BG5 and BV10 onto TDNs/TNTs are examined with an aid of the DKR equation for ion-exchange mechanism, in which the sorption energy lies within 8-16 kJ/mol. The heats of adsorption, calculated from the van't Hoff equation and the adsorption is an exothermic process. Via Boyd kinetic model, implying external mass transport mainly governs the rate-limiting process. From the experimental data of the dye wastewaters removal under ultraviolet light irradiation, the photodegradative efficiencies of four kind of dyes solutions on TDNs/TNTs were Basic Violet 10>Basic Green 5>Methylene Blue>Acid Blue 9. Finally, a simple Langmuir-Hinshelwood was used and calculated by the relationship of ln(C0/Ca) versus time to describe the reactions of the dye wastewaters. Basic Violet 10 photodecomposion rate was the highest photocatalytic efficiency with K of 0.00894/min.

Conventional storage of large amounts of hydrogen in its molecular form is difficult and expensive because it requires employing either extremely high pressure gas or very low temperature liquid. Because of the importance of hydrogen as a fuel, the DOE has set system targets for hydrogen storage of gravimetric (5.5 wt%) and volumetric (40 g L-1) densities to be achieved by 2015. Given that these are system goals, a practical material will need to have higher capacity when the weight of the tank and associated cooling or regeneration system is considered. The size and weight of these components will vary substantially depending on whether the material operates by a chemisorption or physisorption mechanism. In the latter case, metal-organic frameworks (MOFs) have recently been identified as promising adsorbents for hydrogen storage, although little data is available for their sorption behavior. This grant was focused on the study of MOFs with these specific objectives. (1) To examine the effects of functionalization, catenation, and variation of the metal oxide and organic linkers on the low-pressure hydrogen adsorption properties of MOFs. (2) To develop a strategy for producing MOFs with high surface area and porosity to reduce the dead space and increase the hydrogen storage capacity per unit volume. (3) To functionalize MOFs by post synthetic functionalization with metals to improve the adsorption enthalpy of hydrogen for the room temperature hydrogen storage. This effort demonstrated the importance of open metal sites to improve the adsorption enthalpy by the systematic study, and this is also the origin of the new strategy, which termed isoreticular functionalization and metalation. However, a large pore volume is still a prerequisite feature. Based on our principle to design highly porous MOFs, guest-free MOFs with ultrahigh porosity have been experimentally synthesized. MOF-210, whose BET surface area is 6240 m2 g-1 (the highest among porous solids), takes up 15 wt% of total H2 uptake at 80 bar and 77 K. More importantly, the total H2 uptake by MOF-210 was 2.7 wt% at 80 bar and 298 K, which is the highest number reported for physisorptive materials.

Advancing hydrogen storage predictions in metal-organic frameworks: A comparative study of LightGBM and random forest models with data enhancement

The strategy of utilizing mechanochemical synthesis to obtain metal−organic frameworks (MOFs) with high surface areas is demonstrated for two model systems. The compounds HKUST-1 (Cu3(BTC)2, BTC = 1,3,5-benzenetricarboxylate) and MOF-14 (Cu3(BTB)2, BTB = 4,4′,4′′-benzenetribenzoate) were synthesized by ball milling and characterized by powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and thermal analysis (DTA/DTG/MS). The specific surface area (SSA) of both compounds was characterized by nitrogen adsorption. To verify these results and to understand how the synthetic conditions influence the pore structure and the surface area, additional small-angle X-ray scattering (SAXS) experiments were carried out. Our investigations confirm that this synthesis approach is a promising alternative method for distinct MOFs. This facile method leads to materials with surface areas of 1713 m2/g, which is comparable to the highest given values in the literature for the respective comp...

Effective adsorption of sulfamethoxazole, bisphenol A and methyl orange on nanoporous carbon derived from metal-organic frameworks

Enhanced hydrogen sorption in single walled carbon nanotube incorporated MIL-101 composite metal–organic framework

Owing to their high surface area, excellent electrolyte permeability and ample diffusion pathways for charge transport, porous and hollow-structured electrochemically active materials attract more attention as the electrodes. In general, the process of template preparation method is used to achieve hollow structured materials over the last few decades. However, the complicated preparation process including removal of template and surface modification often results in poor uniformity, low reproducibility, and high cost of porous structure. Moreover, it incorporates functional chemicals with specific homogeneity and dispersity into the hollow porous intercrystalline structure. These problems hinder the development and application in energy storage and conversion devices of the diversified porous and hollow-structured materials. The metal-organic frameworks (MOFs), consisting of organic linkers and coordinated inorganic clusters, appear as an excellent collection of porous crystal material series with high surface areas, high porosity, and tunable structures. However, their low conductivity and electrolyte instability limit the further use of MOFs in the field of LIBs. Recently, how electrode materials for Lithium–ion batteries (LIBs) are designed and prepare using MOFs has attracted more attention. The composite materials derived from MOFs including nanostructured porous carbons and metal oxide uaing self-sacrificial template synthetic route not only solves the problem of low conductivity but also maintains the high surface area and porous structure of MOFs, providing abundant active sites for insertion/deinsertion or adsorption/desorption; Furthermore, composite materials derived from MOFs increase the complexity of nanostructures in terms of structural units and chemical components. In particular, large pore volume and open pore structure are critical to loading guest species, accommodating mechanical strains and facilitating mass transport. In this paper, we briefly examined the production of MOF-derived materials for applications in LIBs. The optimization and modification of an MOFs morphology were implemented according to the electrode material requirement for LIBs. Moreover, the preparation of MOFs-derived electrode materials with porous, hollow, or complicated construction and their effects on electrochemical performance were described. Finally, the challenge and trend in production of electrode materials derived from MOFs were analyzed.

Hydrogen is a clean and high-energy fuel, yet its safe and efficient storage remains a key obstacle to widespread adoption. Metal-organic frameworks (MOFs), with their high surface area and tunable porosity, have emerged as promising candidates for solid-state hydrogen storage. In this work, we introduce a graph-based machine learning framework for predicting hydrogen uptake in MOFs by integrating spectral graph theory with data-driven modeling. Molecular structures are represented as weighted graphs from which we extract 20 graph-based descriptors─including Laplacian spectral features, degree statistics, and Zagreb indices─that capture both topological and geometric characteristics of the framework. These interpretable descriptors are used to train multiple regression models on a data set of 3300 MOFs from the Cambridge Structural Database. The XGBoost regressor achieved the highest performance in predicting hydrogen uptake, with a coefficient of determination (R2) of 0.737, RMSE of 0.850% wt, and MAE of 0.433% wt for gravimetric uptake (UG); and a coefficient of determination (R2) of 0.698, RMSE of 4.467 g H2/L, and MAE of 3.045 g H2/L for volumetric uptake (UV). Beyond accurate prediction, the framework enables inverse materials design by identifying graph-based motifs that contribute to improved storage capacity. This integration of chemical graph theory with machine learning provides a scalable, interpretable, and computationally efficient pathway for the discovery of next-generation MOFs tailored for hydrogen storage and other clean energy applications.

Limited conventional energy resources and serious environmental calamities have motivated researchers to find new and efficient sources of energy. The considerable efforts devoted to this end include the development of bio-diesel, solar cells, coal liq-uefaction/gasification technologies, and fuel cells. Hydrogen is considered by many an ideal energy source owing to its renewable and clean energy characteristics. In addition, it mostly produces water, which is eco-friendly compared to the byproducts of many other energy sources [1-6]. To use hydrogen as an energy source, various hydrogen stor -age methods such as the use of metal hydrides, liquefied hydrogen, and adsorption of hydrogen in porous materials have been studied [7-14]. The adsorption of hydrogen in porous materials is particularly suitable for hydrogen storage, which is critical for suit -ably utilizing hydrogen energy, owing to the reversibility and stability of this method. To date, the wide ranging attempts to develop hydrogen storage mechanisms include studies on carbon materials [15-17], metal-organic frameworks, and zeolites [18-21]. Carbon materials offer many advantages for hydrogen storage, such as easy preparation, suitable surface functional groups, low mass density, thermal stability, and hydropho -bicity [22-24]. Carbon aerogels (CAs) in particular have been recognized as potential hydrogen storage materials because of their suitable structural properties, controllable mass densities, high specific surface areas, and mesopore volumes. However, it is neces -sary to modify the surfaces of carbon materials in order to reach the hydrogen storage capacities determined by the US Department of Energy (DOE).Carbon materials containing transition metals such as platinum, copper, vanadium, and nickel exhibit attractive hydrogen storage properties [10,22,25]. Nickel is particularly prom -ising since it is easily obtained on Earth, and it is inexpensive compared to other metals and enhances hydrogen storage properties. Improved hydrogen storage capacities have been obtained with nickel-plated porous carbon nanofibers owing to the spillover of hydrogen molecules onto the metal-carbon interfaces. In general, the presence of nickel particles on carbon materials has been shown to enhance the hydrogen storage capacity [3,9,19].In this work, CAs were chemically activated by KOH to produce well-developed pore structures and ultimately increase the hydrogen storage capacities. Nickel-loaded activated carbon aerogels (ACAs/Ni hybrid materials) with various nickel content were prepared. Ni particles were loaded onto ACAs to introduce hydrogen-favorable active sites onto the ACA surfaces and improve the hydrogen storage capacities.The CAs were prepared using resorcinol as the carbon precursor and formaldehyde as the initiator. Resorcinol (7.5 g) was dissolved in a solution of distilled water (75 mL) and formaldehyde (25 g). Sodium carbonate was then added to this solution, and the mixture was stirred for 3 h in an open container and dried for 3 h at room temperature. Subsequently, the wet gel was dried at 80°C for 48 h and then immersed in an acetone solution for 24 h without stirring. The aerogels were obtained after drying at 80°C for 24 h. Prior to use, the aerogels were carbonized in a furnace with a heating rate of 2°Cmin

Comparative studies of methyl orange adsorption in various metal-organic frameworks by nitrogen adsorption and positron annihilation lifetime spectroscopy

Against the backdrop of rising emissions of greenhouse gasses and the need for sustainable fuel, hydrogen storage has recently become a popular energy storage option due to its many benefits, such as high energy capacity, low concentrations of side products, and relative ease of access. However, hydrogen storage is not perfect and possesses some critical flaws that prevent it from reaching its full potential, which include volatility and flammability. There are many candidates for hydrogen storage and also extant technologies to target hydrogen storage. Among all the ways proposed to store hydrogen, metal-organic frameworks (MOFs) have become increasingly popular because of their exemplary high surface area and adaptable pore structure. This research explores the various developments of MOFs in the field of hydrogen storage and how they may be improved and compared to one another. It will discuss the issues with current MOFs and design procedures and elements, such as making use of void spaces in MOFs. Then it will proceed to explore how MOFs have been enhanced through impregnation, catenation, and open metal sites. Lastly, this review will feature some breakthrough MOFs that have been promising for hydrogen storage.

Synchronous boosting adsorption and desorption efficiency is a great challenge for CO2 adsorption capture, especially for metal–organic frameworks (MOFs) having high adsorption uptakes. Herein, a novel “self‐supporting foam” strategy is proposed to fabricate a thermally conductive MOFs@boron nitride nanosheets (BNNS) composite foam (MOFs@BNNS‐PEI) via polyethyleneimine (PEI) cross‐linkage. The “rebar” BNNS and the “aggregate” MOFs are packed against each other to form a self‐supporting structure, effectively reducing the reliance on polymers to maintain high MOFs loading. Furthermore, this approach enables the successful fabrication of three different types of typical MOFs, including HKUST‐1, MIL‐100(Fe), and ZIF‐8. This unique design maintains a high specific surface area (SSA) of the MOFs foam and generates nitrogen‐rich microporosity contributing to CO2 adsorption. Additionally, PEI serves as a thermal bridge to reduce the interfacial thermal resistance between BNNS and MOFs, accelerating the thermal desorption of CO2 within the MOFs foam. Benefiting from these advantages, the MOFs@BNNS‐PEI exhibits a higher CO2 adsorption capacity (1.35–1.42 times that of pure MOFs) and a significant increase in the desorption rate for CO2 (5.0–5.7 times that of pure MOFs). Thus, the thermally conductive MOFs foam can be a viable option for efficient CO2 capture in practical applications.

NaN3, as a kind of rich-nitrogen energetic material, engaged in the synthesis of hierarchical transition metal (Co/Ni) organic framework materials (MOFs) through a facile hydrothermal reaction, during which aqueous N3 − function groups being as an unique ligand in preparation of novel coordination polymer with the existence of Co2+ (or Ni2+) salts and dicyandiamide. The obtained compounds (Co-eMOF, Ni-eMOF, NiCo-eMOF) were characterized by structure and composition analysis, specific surface area, thermogravimetric analysis (TGA) and crystal X-ray diffraction. The prepared products regardless of the metal cautions (Co, Ni, or coexist Co and Ni), perform a well three-dimensions (3D) nanostructures with spherical shaped monoliths, known as organic framework materials. The as-prepared products with developed porosity demonstrate a high surface area in range of 80∼130 m2/g. XRD patterns for these three examples show similar lattice crystalline, which to an extent matches well with the simulated MOF-74 materials, suggesting profound formation of oriented crystal growth. XPS reveals the compounds all equipped with high nitrogen content (54∼60 at%), which is largely hinging on the contribution from N3 − function groups, suggesting the superiority of NaN3 serving as the rich nitrogen precursor. Accounting for extensive application, we will apply this as-prepared (Co/Ni) MOF materials as one kind of nitrogen-rich precursor and conduct them for further calcination treatment for preparation of graphite-based transition metal carbides (TMC), and it is highly anticipated to achieve efficient activity towards electrocatalysis in our follow-up actions.

Dendritic fibrous nano metal organic framework: A magnetic core-shell structure as high performance material for electrochemical capacitors

Metal-organic frameworks (MOFs) are newly emerging porous materials. Owing to their large surface area and tunable pore size and geometry, they have been studied for applications in gas storage and separation, especially in hydrogen and methane storage and carbon dioxide capture. It has been well established that the high-pressure gravimetric hydrogen-adsorption capacity of an MOF is directly proportional to its surface area. However, MOFs of high surface areas tend to decompose upon activation. In our previous work, we described an approach toward stable MOFs with high surface areas by incorporating mesocavities with microwindows. To extend this work, we now present an isoreticular series of (3,24)-connected MOFs made from dendritic hexacarboxylate ligands, one of which has a Langmuir surface area as high as 6033 m2 g-1. In addition, the gas-adsorption properties of this new isoreticular MOF series have been studied.