Two complementary design strategies, isomorphous ligand replacement and heterocycle doping, have been applied to iteratively enhance the proton conductivity of a metal-organic framework, β-PCMOF2. The resulting materials, PCMOF2/(Pz) and PCMOF2/(Tz) (Pz = 1H-pyrazole, Tz = 1H-1,2,4-triazole), have their proton conduction raised almost 2 orders of magnitude compared to β-PCMOF2. The bulk conductivities of these materials are over 10 S cm at 85 °C and 90% relative humidity (RH), while maintaining the parent MOF structure. A solid state synthetic route for doping 1-D channels is also presented.

From the outset of the study of MOFs as proton conductors, both conductivity and hydrolytic robustness of the materials have needed to be improved. Here, we report a layered magnesium carboxyphosphonate framework, PCMOF10, that shows an extremely high proton conductivity value of 3.55 × 10(-2) S·cm(-1) at 70 °C and 95% RH. Moreover, PCMOF10 is water stable owing to strong Mg phosphonate bonding. The 2,5-dicarboxy-1,4-benzenediphosphonic acid (H6L) linker anchors a robust backbone and has hydrogen phosphonate groups that interact with the lattice water to form an efficient proton transfer pathway.

Using the concept of isomorphous replacement applied to entire ligands, a C(3)-symmetric trisulfonate ligand was substituted with a C(3)-symmetric tris(hydrogen phosphonate) ligand in a proton conducting metal-organic framework (MOF). The resulting material, PCMOF2½, has its proton conduction raised 1.5 orders of magnitude compared to the parent material, to 2.1 × 10(-2) S cm(-1) at 90% relative humidity and 85 °C, while maintaining the parent MOF structure.

Seven isomorphous lanthanide metal-organic frameworks in the PCMOF-5 family, [Ln(HL)(HO)n](HO) (L = 1,2,4,5-tetrakis(phosphonomethyl)benzene, Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) have been synthesized and characterized. This family contains 1-D water-filled channels lined with free hydrogen phosphonate groups and gives a very low activation energy pathway for proton transfer. The lanthanide contraction was employed to systematically vary the unit cell dimensions and tune the proton conducting pathways. LeBail fitting of the crystalline series shows that the crystallographic a-axis, along the channel, can be varied in increments less than 0.02 Å correspondingly shortening the proton transfer pathway. The proton conductivities for the La and Pr complexes were roughly an order of magnitude higher than other members of the series (10 S cm versus 10 S cm). Single crystal structures of the high and low conducting members of the series (La, Pr for high and Ce for low) affirm the structural similarities extend beyond the unit cell parameters to positions of free acid groups and included water molecules. Scanning electron microscopy reveals marked differences in particle size of the different members of the Ln series owing to lattice strain effects induced by changing the lanthanide. Notably, the high conducting La and Pr complexes have the largest particle sizes. This result contradicts any notion that degradation of the MOF at grain boundaries is enabling the observed conductivity as proton conduction dominated by extrinsic pathways would be enabled by small particles (i.e., the La and Pr complexes would be the worst conductors). Proton conductivity measurements of a ball milled sample of the La complex corroborate this result.

Metal-organic frameworks (MOFs) are a class of porous solid, which have a variety of potential applications. Unfortunately, MOFs often lack hydrolytic stability, which hinders their use as viable materials for large scale applications. Though there have been an increasing number of reports proving water stability, this aspect is often ignored and negative results often remain unpublished. As a result, this report has been produced to offer common benchmarks for stability of MOFs to moisture. This will be done by discussing what water stability means--both with regards to the exposure methods and the means of assessing the MOF after exposure. Based on these two criteria, definitions are proposed in order to allow MOFs to be discussed more consistently. The purpose of this report is not to rank existing MOFs based on water stability or for potential application but to promote and facilitate discussion about hydrolytic stability of MOFs.

The alcohol and water-based processing of a perylene diimide (PDI) organic semiconductor into large area and solvent resistant films is reported. The compound, PDIN-H, is an N-annulated PDI dye with...

Current methods for the preparation of heterobifunctional pomalidomide-conjugates rely on methods that are often low yielding and produce intractable byproducts. Herein we describe our strategy for the reliable and succinct...

A crystalline and permanently porous copper phosphonate monoester framework has been synthesized from a tetraaryl trigonal phosphonate monoester linker. This material has a surface area over 1000 m g , as measured by N sorption, the highest reported for a phosphonate-based metal-organic framework (MOF). The monoesters result in hydrophobic pore surfaces that give a low heat of adsorption for CO and low calculated selectivity for CO over N and CH in binary mixtures. By careful manipulation of synthetic conditions, it is possible to selectively remove some of the monoesters lining the pore to form a hydrogen phosphonate while giving an isomorphous structure. This increases the affinity of the framework for CO giving higher ambient uptake, higher heat of adsorption, and much higher calculated selectivity for CO over both N and CH . Formation of the acid groups is noteworthy as complexation with the parent acid gives a different structure.