Selective nitrogen adsorption via backbonding in a metal-organic framework with exposed vanadium sites. # These authors contributed equally to this work Industrial processes prominently feature π-acidic gases, and an adsorbent capable of selectively interacting with these molecules could enable a number of important chemical separations 1-4 . In nature, enzymes, and correspondingly their synthetic analogues, use accessible, reducing metal centers to bind and even activate weakly π-acidic species such as N 2 through backbonding interactions 5-7 , and incorporation of similar moieties into a porous material should give rise to a new mechanism of adsorption for these gaseous substrates 8 .However, synthetic challenges have prevented realization of such a material. Here, we report a metal-organic framework featuring exposed vanadium(II) centers with an electronic configuration and 3d-orbital energies conducive to the back-donation of electron density to weak π-acids, thereby enabling highly selective adsorption. This new adsorption mechanism, together with the presence of a high concentration of available adsorption sites, results in record N 2 capacities and selectivities for the removal of N 2 from mixtures with CH 4 , while further enabling the separation of olefins from paraffins at elevated temperatures.Ultimately, incorporating such π-basic metal centers into tunable porous materials offers a new handle for capturing and activating key molecular species within next-generation adsorbents.The implementation of adsorbent-based technology stands as a promising route toward mitigating the high energy and emission costs associated with current industrial chemical The synthesis of V 2 Cl 2.8 (

Exchange bias is a property of widespread technological utility, but whose underlying mechanism remains elusive, in part because it is rooted in the interaction of coexisting order parameters in the presence of complex magnetic disorder. Here, we show that a giant exchange bias housed within a spin-glass phase arises in a disordered antiferromagnet. The magnitude and robustness of the exchange bias emerges from a convolution of two energetic landscapes-the highly degenerate landscape of the spin-glass biased by the sublattice spin-configuration of the antiferromagnet. The former provides a source of uncompensated moment, while the latter provides a mechanism for its pinning, leading to the exchange bias. Tuning the relative strength of the spin-glass and antiferromagnet order parameters reveals a principle for tailoring the exchange bias, with potential applications to spintronic technologies.

Co 3 Sn 2 S 2 is a ferromagnetic Weyl semimetal that has been the subject of intense scientific interest due to its large anomalous Hall effect. We show that the coupling of this material's topological properties to its magnetic texture leads to a strongly exchange biased anomalous Hall effect. We argue that this is likely caused by the coexistence of ferromagnetism and spin glass phases, the latter being driven by the geometric frustration intrinsic to the Kagome network of magnetic ions.

Process development work to provide an efficient, robust, and cost-effective manufacturing route to avibactam, a β-lactamase inhibitor is presented herewith. Aspects of this optimization work include the counterintuitive introduction of a protecting group to effect a difficult urea formation and the use of controlled feed hydrogenation conditions to facilitate an elegant one pot debenzylation and sulfation reaction. Overall, the commercial process delivers avibactam in much improved yield with significant reduction in the environmental footprint.

Developing O 2 -selective adsorbents that can produce high-purity oxygen from air remains a significant challenge. Here, we show that chemically reduced metal−organic framework materials of the type A x Fe 2 (bdp) 3 (A = Na + , K + ; bdp 2− = 1,4benzenedipyrazolate; 0 < x ≤ 2), which feature coordinatively saturated iron centers, are capable of strong and selective adsorption of O 2 over N 2 at ambient (25 °C) or even elevated (200 °C) temperature. A combination of gas adsorption analysis, singlecrystal X-ray diffraction, magnetic susceptibility measurements, and a range of spectroscopic methods, including 23 Na solid-state NMR, Mossbauer, and X-ray photoelectron spectroscopies, are employed as probes of O 2 uptake. Significantly, the results support a selective adsorption mechanism involving outer-sphere electron transfer from the framework to form superoxide species, which are subsequently stabilized by intercalated alkali metal cations that reside in the one-dimensional triangular pores of the structure. We further demonstrate O 2 uptake behavior similar to that of A x Fe 2 (bdp) 3 in an expanded-pore framework analogue and thereby gain additional insight into the O 2 adsorption mechanism. The chemical reduction of a robust metal−organic framework to render it capable of binding O 2 through such an outer-sphere electron transfer mechanism represents a promising and underexplored strategy for the design of next-generation O 2 adsorbents.