posted on 2024-02-01, 17:44authored byShao-Min Wang, Mohana Shivanna, Su-Tao Zheng, Tony Pham, Katherine A. Forrest, Qing-Yuan Yang, Qingqing Guan, Brian Space, Susumu Kitagawa, Michael J. Zaworotko
Separating
ethane (C2H6) from ethylene
(C2H4) is an essential and energy-intensive
process
in the chemical industry. Here, we report two flexible diamondoid
coordination networks, X-dia-1-Ni and X-dia-1-Ni0.89Co0.11, that exhibit gate-opening between narrow-pore (NP) and large-pore
(LP) phases for C2H6, but not for C2H4. X-dia-1-Ni0.89Co0.11 thereby exhibited a type
F–IV isotherm at 273 K with no C2H6 uptake
and a high uptake (111 cm3 g–1, 1 atm)
for the NP and LP phases, respectively. Conversely, the LP phase exhibited
a low uptake of C2H4 (12.2 cm3 g–1). This C2H6/C2H4 uptake ratio of 9.1 for X-dia-1-Ni0.89Co0.11 far
surpassed those of previously reported physisorbents, many of which
are C2H4-selective. In situ variable-pressure X-ray diffraction and modeling studies provided
insight into the abrupt C2H6-induced structural
NP to LP transformation. The promise of pure gas isotherms and, more
generally, flexible coordination networks for gas separations was
validated by dynamic breakthrough studies, which afforded high-purity
(99.9%) C2H4 in one step.