Molecular States of O₂ Confined in a Carbon Nanospace from the Low-Temperature Magnetic Susceptibility

Abstract

The magnetic susceptibility of O2 adsorbed in micropores of activated carbon fibers (ACFs) having different micropore widths was measured at a wide temperature range of 1.7-100 K. The micropore structure of ACF was determined by the analysis of the N2 adsorption isotherm at 77 K. The adsorption isotherm of O2 on ACF at 77 K was determined and it was shown that O2 is adsorbed in the micropore in a similar way to N2 from the Dubinin-Radushkevich analysis of O2 and N2 adsorption isotherms. The -T relation suggested the presence of three kinds of O2 molecular states in the micropore, that is, the isolated, the cluster, and condensed states; their stable region changes with the fractional filling and the temperature. Although the potential energy difference of the O2-surface interaction of different pore systems is only 150 K by the potential calculation, the magnetic susceptibility measurement can sufficiently evidence distinctly the presence of different states of O2 molecules in the micropore.

Functional Porous Coordination Polymers

“…128, 229, 292, 310, 318, 398 O 2 and NO are among the smallest stable paramagnetic molecules under ambient conditions and have the potential to form new molecular‐based magnetic and dielectric materials. However, many attempts to form 1D arrays of these paramagnetic gas molecules through confinement of the molecules in porous coordination polymers399 as well as carbon materials400, 401 were not successful. Unlike aromatic and polar molecules which can take part in intermolecular interactions, such as π–π stacking and hydrogen bonding, these simple molecules can only enter into weak van der Waals force interactions which are not strong enough to form 1D assemblies.…”

Funktionale poröse Koordinationspolymere

“…[391] neue molekulare magnetische und dielektrische Materialien. Allerdings sind viele Ansätze, 1D-Aggregate dieser Moleküle in porösen Koordinationspolymeren [399] und Kohlenstoffmaterialien [400,401] ). Die antiferromagnetische Wechselwirkung wird zu J/k B % À50 K bestimmt; der Wert ist größer als der der a-Phase mit J/k B % À30 K (H = À2 J S 1 S 2 ).…”

Formation of a One-Dimensional Array of Oxygen in a Microporous Metal-Organic Solid

“…In spite of many ex-perimental and theoretical investigations, the adsorption mechanism and ordering state of adsorbed O 2 molecules that form a specific array in nanochannels are not yet clear (3,4). In the past decade, various novel nanochannel structures constructed with metal-organic frameworks have been produced and studied with regard to their adsorption performance with various gas molecules (5)(6)(7)(8).…”