8 research outputs found
Proton conduction in a phosphonate-based metal-organic framework mediated by intrinsic âfree diffusion inside a sphereâ
Understanding the molecular mechanism of proton conduction is crucial for the design of new materials with improved conductivity. Quasi-elastic neutron scattering (QENS) has been used to probe the mechanism of proton diffusion within a new phosphonate-based metalâorganic framework (MOF) material, MFM-500(Ni). QENS suggests that the proton conductivity (4.5 Ă 10â4 S/cm at 98% relative humidity and 25 °C) of MFM-500(Ni) is mediated by intrinsic âfree diffusion inside a sphereâ, representing the first example of such a mechanism observed in MOFs
Locating the Binding Domains in a Highly Selective Mixed Matrix Membrane via Synchrotron IR Microspectroscopy
The binding domains within a mixed matrix membrane (MMM) that is selective for CO2 comprising MFM-300(Al) and the polymer 6FDA-Durene-DABA have been established via in situ synchrotron IR microspectroscopy. The MOF crystals are fully accessible and play a critical role in the binding of CO2, creating a selective pathway to promote permeation of CO2 within and through the MMM. This study reveals directly the molecular mechanism for the overall enhanced performance of this MMM in terms of permeability, solubility and selectivity for CO2
Modulating proton diffusion and conductivity in metal-organic frameworks by incorporation of accessible free carboxylic acid groups
Three multi-carboxylic acid functionalised ligands have been designed, synthesised and utilised to prepare the new barium-based MOFs, MFM-510, -511, and -512, which show excellent stability to water-vapour. MFM-510 and MFM-511 show moderate proton conductivities (2.1 Ă 10â5 and 5.1 Ă 10â5 S cmâ1, respectively) at 99% RH and 298 K, attributed to the lack of free protons or hindered proton diffusion within the framework structures. In contrast, MFM-512, which incorporates a pendant carboxylic acid group directed into the pore of the framework, shows a two orders of magnitude enhancement in proton conductivity (2.9 Ă 10â3 S cmâ1). Quasi-elastic neutron scattering (QENS) suggests that the proton dynamics of MFM-512 are mediated by âfree diffusion inside a sphereâ confirming that incorporation of free carboxylic acid groups within the pores of MOFs is an efficient albeit synthetically challenging strategy to improve proton conductivity
Proton conduction in a phosphonate-based metal-organic framework mediated by intrinsic âfree diffusion inside a sphereâ
Understanding the molecular mechanism of proton conduction is crucial for the design of new materials with improved conductivity. Quasi-elastic neutron scattering (QENS) has been used to probe the mechanism of proton diffusion within a new phosphonate-based metalâorganic framework (MOF) material, MFM-500(Ni). QENS suggests that the proton conductivity (4.5 Ă 10â4 S/cm at 98% relative humidity and 25 °C) of MFM-500(Ni) is mediated by intrinsic âfree diffusion inside a sphereâ, representing the first example of such a mechanism observed in MOFs
CCDC 1450011: Experimental Crystal Structure Determination
An entry from the Cambridge Structural Database, the worldâs repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures
CCDC 1450010: Experimental Crystal Structure Determination
An entry from the Cambridge Structural Database, the worldâs repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures
Enhancement of Proton Conductivity in Nonporous Metal-Organic Frameworks:The Role of Framework Proton Density and Humidity
Owing
to their inherent pore structure, porous metalâorganic
frameworks (MOFs) can undergo postsynthetic modification, such as
loading extra-framework proton carriers. However, strategies for improving
the proton conductivity for nonporous MOFs are largely lacking, although
increasing numbers of nonporous MOFs exhibit promising proton conductivities.
Often, high humidity is required for nonporous MOFs to achieve high
conductivities, but to date no clear mechanisms have been experimentally
identified. Here we describe the new materials MFM-550Â(M), [MÂ(HL1)], (H4L1 = biphenyl-4,4âČ-diphosphonic
acid; M = La, Ce, Nd, Sm, Gd, Ho), MFM-550Â(Ba), [BaÂ(H2L1)], and MFM-555Â(M), [M(HL2)], (H4L2 = benzene-1,4-diphosphonic acid; M = La, Ce, Nd, Sm,
Gd, Ho), and report enhanced proton conductivities in these nonporous
materials by (i) replacing the metal ion to one with a lower oxidation
state, (ii) reducing the length of the organic ligand, and (iii) introducing
additional acidic protons on the MOF surface. Increased framework
proton density in these materials can lead to an enhancement in proton
conductivity of up to 4 orders of magnitude. Additionally, we report
a comprehensive investigation using in situ 2H NMR and
neutron spectroscopy, coupled with molecular dynamic modeling, to
elucidate the role of humidity in assembling interconnected networks
for proton hopping. This study constructs a relationship between framework
proton density and the corresponding proton conductivity in nonporous
MOFs, and directly explains the role of both surface protons and external
water in assembling the proton conduction pathways