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In a world where capture and separation processes represent above 10% of global energy consumption, novel porous materials, such as Metal-Organic Frameworks (MOFs) used in adsorption-based processes are a promising alternative to dethrone the high-energy-demanding distillation. Shape and size tailor-made pores in combination with Lewis acidic sites can enhance the adsorbate-adsorbent interactions. Understanding the underlying mechanisms of adsorption is essential to designing and optimizing capture and separation processes. Herein, we analyze the adsorption behaviour of light hydrocarbons (methane, ethane, ethylene, propane, and propylene) in two synthesized copper-based MOFs, Cu-MOF-74 and URJC-1. The experimental and computational adsorption curves reveal a limited effect of the exposed metal centers on the olefins. The lower interaction Cu-olefin is also reflected in the calculated enthalpy of adsorption and binding geometries. Moreover, the diamond-shaped pores' deformation upon external stimuli is first reported in URJC-1. This phenomenon is highlighted as the key to understanding the adsorbent's responsive mechanisms and potential in future industrial applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Highly porous composites were synthesized via facile crystallization of a metal-organic framework (MOF) in mesopores of a three-dimensional (3D) graphene (MG). First, MG was prepared via facile thermal exfoliation of graphite oxide in air, which enabled sufficient separation of graphene sheets in the form of an interconnected 3D structure. Next, aluminum-based MOF [MOF520: Al 8 (OH) 8 (BTB) 4 (HCOO) 4 , BTB = 4,4′,4"-benzene-1,3,5-tryil-tribenzoate] was predominantly crystallized in mesopores of 3D structure having a large pore volume. The resulting MG-MOF composites possessed specific surface areas and pore volumes between those of MG (640 m2/g and 3.0 cm3/g) and MOF (3160 m2/g and 1.3 cm3/g). The composite consisting of MG and MOF with a weight ratio of 1:2 showed almost twice-larger benzene adsorption capacity, i.e., 24.5 mmol/g at 20 °C and relative pressure close to unity, in comparison to that of pure MOF. Although at the same conditions the pure MG captured an ultrahigh amount of benzene, i.e., 33.6 mmol/g, adsorption of this adsorbate at low and moderate relative pressures was much lower than that on pure MOF. Thus, the MG-MOF composites featured much better benzene adsorption performance in a wide range of relative pressures as compared to pure MG and MOF, respectively. Additionally, the composites featured better thermal stability in comparison to the pristine MOF. The use of MG in this synthesis method afforded the well-dispersed, small crystals of MOF, which is essential for the design of MOF-based composites. Graphical abstract Image 1 Highlights • Crystallization of MOF in mesopores of a three-dimensional graphene. • Enhancement of C 6 H 6 adsorption by adding mesoporous graphene to MOF. • Ultrahigh C 6 H 6 adsorption of 24.5 mmol/g on graphene-MOF composite at 20 °C. [ABSTRACT FROM AUTHOR]

This work constitutes a guide towards the preparation of metal-organic framework materials (MOF) supported and/or confined in activated carbon monoliths (ACM). The resulting hybrid porous materials exhibit improved physico-chemical properties as compared with their parent constituents. The different hybrids were obtained exploring several experimental approaches, which were thoroughly discussed. All hybrids were characterized by N 2 adsorption isotherms, SEM, TGA and XRD techniques. The characterization studies pointed out that the preparation conditions are of paramount importance in defining the nucleation and growth of HKUST-1, either outside of the carbon grains (surface coating), and/or in the internal pores (bulk confinement). While the surface coating was achieved by directly synthesizing the MOF in presence of the ACM (i.e. in-situ synthesis), bulk confinement is favored after applying an additional step that involves a pre-nucleation at low temperatures (5 °C). The hybrid material with the best performance, sample A5(1), shows enhanced mechanical properties compared to its parent counterparts, combined with high apparent surface area (up to 1300 m 2 /g), an improved crushing strength (about 8 times superior to ACM) and a geometrical density of around 0.45 cm 3 /g, which almost duplicates that of ACM. Last but not least, the adsorption behavior of the hybrid was tested for CO 2 and CH 4 adsorption. Application of IAST equation to the single component adsorption isotherms at room temperature gives rise to a CO 2 /CH 4 selectivity factor of 5.5 in the hybrid material, larger than that on ACM (S = 3.5). [ABSTRACT FROM AUTHOR]

Methane adsorption was studied in microporous materials with differences in their pore geometry and surface chemistry in order to evaluate the characteristics that enhance methane storage in porous materials. The studied materials included metal-organic frameworks (Cu-BTC, MIL-53 and ZIF-8), zeolites (5A and 13X) and an activated carbon (Maxsorb). Textural properties such as pore volume and specific surface area were studied by nitrogen adsorption–desorption isotherms. Methane adsorption was analyzed by means of measurements at low and high pressures (0–5000 kPa) at various temperatures (278–323 K). The effect of the adsorbate–adsorbent interaction was evaluated by the determination of the Henry constant using the adsorption data of methane at low pressures and 298 K. In addition, the isosteric enthalpy of adsorption using data of adsorption at several temperatures was obtained. A linear trend was observed between the Henry constant, the enthalpy of adsorption and the pore size, indicating that the latter is the most influential factor in the interaction of a microporous adsorbent and methane at room temperature. Also, it was found that the textural properties (i.e. specific surface and micropore volume) are directly related with the methane storage capacity at 298 K and 3.5 MPa. However, we obtained a deviation of this behavior for ZIF-8 that is related to its geometry and pore size. [ABSTRACT FROM AUTHOR]

In this study, the possible applications of Cr-doped UiO-66 in adsorption heat transformation (AHT) were investigated. Four different Cr-doped UiO-66 samples were prepared to examine their structures and water adsorption properties. Results showed that Cr-doped UiO-66 samples have higher pore volume and specific surface area than pure UiO-66 samples. In particular, 0.2Cr-UiO-66 has the highest BET specific surface area (993 m2/g) and micropore volume (0.50 cm3/g), which are 31.6% and 29.6% higher than those of unmodified UiO-66, respectively. Water adsorption tests revealed that Cr doping can improve the water adsorption performances of UiO-66. At 25 °C and P/P 0 = 0.9, the saturated water uptake of 1.0Cr-UiO-66 is 0.69 g/g, which is 64.3% higher than that of pure UiO-66. After 10 adsorption/desorption cycles, the water adsorption capacity of pure UiO-66 and 0.5Cr-UiO-66 samples has decreased by 3.4% and 5.7%, respectively, indicating their good cycle stability. All these results indicate that Cr doping is beneficial to UiO-66 application in AHT. [Display omitted] • Metal-organic framework UiO-66 were modified with Cr by solvothermal method. • Cr-doped UiO-66 showed enhanced saturated water adsorption capacity and water uptake at low water pressure. • The BET specific surface area of UiO-66 was increased by 31.5% with the addition of Cr. • Water adsorption capacity of 0.5Cr-UiO-66 remains most constant after cycling. [ABSTRACT FROM AUTHOR]

Abstract: High pressure excess adsorption isotherms of sulfur hexafluoride (SF6) and tetrafluoromethane (CF4) on metal–organic frameworks Cu3(btc)2 (HKUST-1, btc – benzene-1,3,5-tricarboxylate), Fe3FO(H2O)2(btc)3 (MIL-100), Cr3F(H2O)2O(1,4-bdc)3 (MIL-101, 1,4-bdc – 1,4-benzenedicarboxylate), Co2(1,4-bdc)2(dabco) (dabco-1,4-diazabicyclo[2.2.2]octane), Ni2(2,6-ndc)2(dabco) (DUT-8, 2,6-ndc – 2,6-naphthalenedicarboxylate), Ni2O5(btb)2 (DUT-9, btb – benzene-1,3,5-tribenzoate), Zn4O(btb), and (Zn4O(dmcpz)3) (dmcpz – 3,5-dimethyl-4-carboxypyrazolato) at 298K were investigated using volumetric methods. Up to 1bar pressure (at 298K), microporous MOF with open metal sites HKUST-1 shows the best performance in SF6 adsorption and microporous Zn4O(dmcpz)3 in CF4 adsorption. At high pressure, mesoporous MIL-101 and DUT-9 have the highest storage capacities for both gases among the MOFs investigated. [Copyright &y& Elsevier]

Abstract: Hydrogen and deuterium adsorption sites in the crystalline MOF copper(II) benzene-1,3,5-tricarboxylate, Cu–BTC were studied by low-temperature thermal desorption spectroscopy. For a maximum loading of 218 D2 molecules per unit cell of Cu–BTC three desorption maxima were observed. The maxima could be separated by either interrupted desorption or partial loading. By comparing to neutron diffraction studies from the literature the maxima could be assigned to three different adsorption sites, i.e. coordinatively-unsaturated Cu2+ sites, tetrahedral side pockets and the large pores. [Copyright &y& Elsevier]

A review of the synthesis, structure, and properties of metal–organic frameworks (MOFs) is presented, highlighting the important advances in their research over the past decade. This new class of porous materials is attracting attention due to demonstrations of their large pore sizes, high apparent surface areas, selective uptake of small molecules, and optical or magnetic responses to the inclusion of guests. More importantly, their synthesis from molecular building blocks holds the potential for directed tailoring of these properties. [Copyright &y& Elsevier]

Hf- and Zr-based metal-organic frameworks are highly stable and porous materials that have been attracted in many applications, especially in biomedicine. The materials are commonly synthesized via solvothermal reaction between Hf or Zr salts and organic linkers, however this method requires elongated reaction time as well as results in heterogeneous particles and low yield, which leads to the difficulty for nano MOF synthesis. To overcome these disadvantages, we applied microwave method to enhance the synthetic efficiency and control particle homogeneity of nano UiO-66 framework. The nano MOFs, named Hf-UiO-66 and Zr-UiO-66, with highly homogeneous nanoparticles, very small sizes and high yields could be formed under microwave irradiation within a few minutes. According to the results from XRD, SEM, N 2 isotherm sorption, and TGA characterizations, the materials exhibited similar porosity and structure compared to the original framework. Additionally, Hf-UiO-66 and Zr-UiO-66 showed high efficiency for the treatment of curcumin's overdose by adsorbing the drug from aqueous solution with a maximum adsorption capacity up to 463.02 and 466.39 mg g−1, respectively, higher than reported Zr-UiO-66 (393.22 mg g−1). Moreover, the adsorption mechanisms were revealed that the adsorption of curcumin (CUR) by UiO-66 was influenced by defect sites in the MOF structure. UiO-66 (Hf and Zr) frameworks synthesized under microwave irradiation for curcumin adsorption. Image 1 • Microwave method is developed for effective and fast synthesis of nano metal-organic frameworks (named Hf- and Zr-UiO-66). • Particle sizes of these materials could be less than 50 nm. • The materials show higher efficiency for curcumin adsorption. • Kinetics and thermodynamics of curcumin adsorption on the MOFs were studied. • Adsorption mechanism was demonstrated by quantum mechanical calculations. [ABSTRACT FROM AUTHOR]