Pristine MOF Research Articles

MOF-aminoclay composites for superior CO2 capture, separation and enhanced catalytic activity in chemical fixation of CO2.

We delineate the growth and stabilization of ultra-small (2-3 nm) {Cu3(BTC)2(H2O)2·xH2O} MOF nanoparticles on a 2D layered aminoclay template. The composite shows significant CO2 uptake (5.35 mmol g-1 at 298 K, 1 bar; 46% higher than pristine bulk MOF), superior CO2 separation efficiency from CO2/N2 and CO2/CH4 mixtures and higher catalytic proficiency for chemical fixation of CO2 into cyclic carbonates.

In-situ observation for growth of hierarchical metal-organic frameworks and their self-sequestering mechanism for gas storage.

Although structures with the single functional constructions and micropores were demonstrated to capture many different molecules such as carbon dioxide, methane, and hydrogen with high capacities at low temperatures, their feeble interactions still limit practical applications at room temperature. Herein, we report in-situ growth observation of hierarchical pores in pomegranate metal-organic frameworks (pmg-MOFs) and their self-sequestering storage mechanism, not observed for pristine MOFs. Direct observation of hierarchical pores inside the pmg-MOF was evident by in-situ growth X-ray measurements while self-sequestering storage mechanism was revealed by in-situ gas sorption X-ray analysis and molecular dynamics simulations. The results show that meso/macropores are created at the early stage of crystal growth and then enclosed by micropore crystalline shells, where hierarchical pores are networking under self-sequestering mechanism to give enhanced gas storage. This pmg-MOF gives higher CO2 (39%) and CH4 (14%) storage capacity than pristine MOF at room temperature, in addition to fast kinetics with robust capacity retention during gas sorption cycles, thus giving the clue to control dynamic behaviors of gas adsorption.

Ionized Zr-MOFs for highly efficient post-combustion CO2 capture

In this study, a previously reported Zr-MOF UiO-66(Zr)-(COOH)2 with optimal features for CO2 capture was ionized by neutralization with aqueous MOH solutions (M=Li+, Na+, K+). This post-synthetic modification route has endowed some of the resulting MOFs with higher CO2 uptake capacity. The CO2/N2 selectivity of UiO-66(Zr)-(COOK)2 calculated by Ideal Adsorption Solution Theory (IAST) demonstrates a significant enhancement of 83% compared with the pristine MOF. In addition, dynamic column breakthrough experiments were performed using a binary CO2/N2 mixed gas with a molar ratio of 15:85 to mimic the flue gas composition. The CO2/N2 selectivity of UiO-66(Zr)-(COONa)2 calculated based on breakthrough data is 99.6, which is among the highest CO2/N2 selectivities obtained experimentally using binary mixed gas breakthrough/co-adsorption experiments. Our results strongly confirm that ionization is an effective way of introducing strong CO2 adsorption sites into MOFs for higher CO2-MOF interactions and better CO2 separation performance.

New copper/GO based material as an efficient oxygen reduction catalyst in an alkaline medium: The role of unique Cu/rGO architecture

A new hybrid Cu/rGO catalyst obtained by a thermal treatment of the composite of a copper-based MOF with graphite oxide exhibited a marked catalytic activity for oxygen reduction reaction (ORR) in an alkaline medium, high tolerance to methanol oxidation and superior long-term stability over 20h. The unique architecture of the copper atoms in the 3D framework of the pristine MOF coupled with the excellent electron transfer properties of rGO lead to materials with a homogenous distribution of copper nanoparticles of specific chemistry assembled within the graphene sheets. Fast O2 adsorption and charge transfer owing to the strong interactions between copper atoms and graphite oxide resulted in highly stable and active Cu/rGO electrodes, compared to the carbonized MOF. The synergistic effect of copper and rGO in the composite leads to a superior ORR activity in terms of long-term stability and high current densities, close to the best performance reported for Pt and other metal-free electrocatalysts.

Tuning of gate adsorption: modification of a flexible metal-organic framework by secondary organic ligands.

For realizing selective adsorption of targeted molecules, a flexible metal-organic framework (MOF) was modified with monodentate secondary ligands. Although the modified MOF retains CO2 adsorptivities with a vertical adsorption uptake, the material also shows gate adsorptivities of a specific gas molecule that the pristine MOF does not adsorb.

Growth of 2D sheets of a MOF on graphene surfaces to yield composites with novel gas adsorption characteristics

Homogeneous graphene-MOF composites based on a 2D pillared-bilayer MOF (Cd-PBM), {[Cd4(azpy)2(pyrdc)4(H2O)2]·9H2O}n (azpy = 4,4'-azopyridine, pyrdc = pyridine-2,3-dicarboxylate), have been synthesized, using both graphene oxide (GO) and benzoic acid functionalized graphene (BFG). The composites GO@Cd-PBM and BFG@Cd-PBM demonstrate growth of the 2D nano-sheets of MOF on the graphene surface. While the pristine MOF, Cd-PBM shows selective CO2 uptake with a single-step type-I adsorption profile, the composites show stepwise CO2 uptake with a large hysteresis. With H2O and MeOH, on the other hand, the composites show a single-step adsorption unlike the parent MOF.

Magnesium Nanocrystals Embedded in a Metal–Organic Framework: Hybrid Hydrogen Storage with Synergistic Effect on Physi‐ and Chemisorption

Hexagonal-disk-shaped magnesium nanocrystals (MgNCs) are fabricated within a porous metal-organic framework (MOF, see picture). The MgNCs@MOF stores hydrogen by both physi- and chemisorptions, exhibiting synergistic effects to decrease the isosteric heat of H(2) physisorption compared with that of pristine MOF, and decrease the H(2) chemisorption/desorption temperatures by 200 K compared with those of bare Mg powder.

Electrochemistry nanometric patterning of MOF particles: Anisotropic metal electrodeposition in Cu/MOF

Electrodeposition of copper from Cu/MOF immersed into acetate buffer produces a quasi-periodic series of 10–20 nm sized laminae sandwiched within the pristine MOF lattice as monitored by voltammetry of microparticles/atomic force microscopy. This anisotropic patterning can be qualitatively described in terms of a highly orientation-dependent diffusion of electrons and charge-balancing electrolyte counterions in the MOF network.