Computation-informed optimization of Ni(PyC)2 functionalization for noble gas separations

Abstract

Our objective is to tune a “lead” metal-organic framework, Ni(PyC) 2 (pyridine-4-carboxylate [PyC]), by functionalizing its PyC ligands to maximize its adsorptive selectivity for xenon over krypton at room temperature. To guide experiments, we (1) construct a library of Ni(PyC-X) 2 (X = functional group) crystal structure models then (2) use molecular simulations to predict their noble gas adsorption and selectivity at room temperature. Motivated by our virtual screening, we synthesize Ni(PyC- m -NH 2 ) 2 , determine its crystal structure by X-ray powder diffraction, measure its Xe, Kr, and Ar adsorption isotherms (298 K), and indeed find that its dilute Xe/Kr selectivity at 298 K (20) exceeds that of its parent Ni(PyC) 2 (17). Corroborated by molecular models, in situ X-ray diffraction shows that Ni(PyC- m -NH 2 ) 2 organizes well-defined, Xe-tailored binding pockets along its one-dimensional channels. Our study illustrates the computation-informed optimization of a “lead” metal-organic framework. • Virtual screening of Ni(PyC-X) 2 MOFs for Xe/Kr separations at room temperature • Synthesize, determine structure of, and measure Xe, Kr, Ar adsorption in Ni(PyC- m -NH 2 ) 2 • Ni(PyC- m -NH 2 ) 2 exhibits a dilute Xe/Kr selectivity (298 K) higher than Ni(PyC) 2 • The channels of Ni(PyC- m -NH 2 ) 2 present well-defined Xe binding pockets Gantzler et al. find that virtual screening of functionalized Ni(PyC) 2 analogs for Xe/Kr separations at room temperature highlights Ni(PyC- m -NH 2 ) 2 . They synthesize Ni(PyC- m -NH 2 ) 2 , determine its structure, and measure its noble gas adsorption isotherms, confirming that Ni(PyC- m -NH 2 ) 2 exhibits a higher Xe/Kr selectivity than Ni(PyC) 2.