Quantification of residual organic bases in an active pharmaceutical ingredient using mixed-mode chromatography and UV detection.

The use of organic bases is ubiquitous in chemical synthesis, yet quantifying these compounds with traditional HPLC methodologies is often hampered by poor peak shape, low retention, and limited UV absorption. When employed in the manufacture of an active pharmaceutical ingredient (API), these compounds must be controlled to levels that are safe for human consumption, requiring robust analytical methods with sufficiently low quantification limits. This work describes the development of an HPLC method for the quantification of imidazole and 1,8-Diazabicyclo[5.

Transient Catenation in a Zirconium-Based Metal-Organic Framework and Its Effect on Mechanical Stability and Sorption Properties.

Interpenetration of two or more sublattices is common among many metal-organic frameworks (MOFs). Herein, we study the evolution of one zirconium cluster-based, 3,8-connected MOF from its non-interpenetrated (NU-1200) to interpenetrated (STA-26) isomer. We observe this transient catenation process indirectly using ensemble methods, such as nitrogen porosimetry and X-ray diffraction, and directly, using high-resolution transmission electron microscopy.

Proton Conductivity via Trapped Water in Phosphonate-Based Metal-Organic Frameworks Synthesized in Aqueous Media.

Metal-organic frameworks (MOFs) are promising candidates for proton-conducting applications. Herein, we report the aqueous synthesis of two new phosphonate-based MOFs comprising glyphosate linkers, [Mg(dpmp)]·2HO (Mg-NU-225) and [Fe(dpmp)]·2HO (Fe-NU-225), (dpmp = ,'-diphosphonomethyl-2,5-piperazinedione), and explore their proton conductivities. Single crystal X-ray diffraction measurements revealed that both frameworks display a two-dimensional layered structure with a cyclic ring ligand which forms from the condensation of two glyphosate molecules.

Enhancing Four-Carbon Olefin Production from Acetylene over Copper Nanoparticles in Metal-Organic Frameworks.

Four-carbon olefins, such as 1-butene and 1,3-butadiene, are important chemical feedstocks for the production of adhesives and synthetic rubber. These compounds are found in the C fraction of "green oil" products that can arise during the hydrogenation of acetylene. Here, we demonstrate that control of the catalyst structure increases the yield and productivity of these important olefins with a family of catalyst materials comprising Cu nanoparticles (CuNPs) bound within the pores of Zr-based metal-organic frameworks.

Balancing volumetric and gravimetric uptake in highly porous materials for clean energy.

A huge challenge facing scientists is the development of adsorbent materials that exhibit ultrahigh porosity but maintain balance between gravimetric and volumetric surface areas for the onboard storage of hydrogen and methane gas-alternatives to conventional fossil fuels. Here we report the simulation-motivated synthesis of ultraporous metal-organic frameworks (MOFs) based on metal trinuclear clusters, namely, NU-1501-M (M = Al or Fe). Relative to other ultraporous MOFs, NU-1501-Al exhibits concurrently a high gravimetric Brunauer-Emmett-Teller (BET) area of 7310 m g and a volumetric BET area of 2060 m cm while satisfying the four BET consistency criteria.

Mechanical properties of metal-organic frameworks.

As the field of metal-organic frameworks (MOFs) continues to grow, the physical stability and mechanical properties of these porous materials has become a topic of great interest. While strategies for synthesizing MOFs with desirable chemical functionalities or pore sizes have been established over the past twenty years, design principles to modulate the response of MOFs to mechanical stress are still underdeveloped. The inherent porosity of these frameworks results in many interesting and sometimes unexpected phenomena upon exposure to elevated pressures and other physical stimuli.

A Flexible Interpenetrated Zirconium-Based Metal-Organic Framework with High Affinity toward Ammonia.

Flexible metal-organic frameworks (MOFs) are highly attractive porous crystalline materials presenting structural changes when exposed to external stimuli, the mechanism of which is often difficult to glean, owing to their complex and dynamic nature. Herein, a flexible interpenetrated Zr-MOF, NU-1401, composed of rare 4-connected Zr nodes and tetratopic naphthalenediimide (NDI)-based carboxylate linkers, was designed. The intra-framework pore opening deformation and inter-framework motions, when subjected to different solvent molecules, were investigated by single-crystal XRD.

Porosity Dependence of Compression and Lattice Rigidity in Metal-Organic Framework Series.

Porous materials, including metal-organic frameworks (MOFs), are known to undergo structural changes when subjected to applied hydrostatic pressures that are both fundamentally interesting and practically relevant. With the rich structural diversity of MOFs, the development of design rules to better understand and enhance the mechanical stability of MOFs is of paramount importance. In this work, the compressibilities of seven MOFs belonging to two topological families (representing the most comprehensive study of this type to date) were evaluated using in situ synchrotron X-ray powder diffraction of samples within a diamond anvil cell.

A Flexible Metal-Organic Framework with 4-Connected Zr Nodes.

Zr-based metal-organic frameworks (MOFs) have been known for their excellent stability; however, due to the high connectivity of the Zr nodes, it is challenging to introduce flexibility into Zr-MOFs. Here we present a flexible Zr-MOF named NU-1400 comprising 4-connected Zr nodes and tetratopic linkers. It exhibits guest-dependent structural flexibility with up to 48% contraction in the unit cell volume as evidenced by single-crystal X-ray diffraction studies.

Calcium(ii)-catalyzed enantioselective conjugate additions of amines.

The direct enantioselective chiral calcium(ii)·phosphate complex (Ca[CPA])-catalyzed conjugate addition of unprotected alkyl amines to maleimides was developed. This mild catalytic system represents a significant advance towards the general convergent asymmetric amination of α,β-unsaturated electrophiles, providing medicinally relevant chiral aminosuccinimide products in high yields and enantioselectivities. Furthermore, the catalyst can be reused directly from a previously chromatographed reaction and still maintain both high yield and selectivity.