Multiple Structural and Phase Transformations of MOF and Selective Hydrocarbon Gas Separation in its Amorphous, Glass Phase States

The first wide‐view image of multiple structural and phase transformations for MOFs from crystal state transformations further to the extreme limit approaching liquid/glass phase, was presented based on a square‐layer framework of [Co2(pybz)2(CH3COO)2]·DMF (Co2). The process involves i) an initial crystalline transformation brings to a 3‐fold interpenetrated and ordered vacancies contained framework [Co(pybz)2(CH3OH)2]·2CH3OH (CoM) due to in‐situ disassemble‐reassemble, ii) thermal induced departure of a pair of cis‐form coordinated methanol in CoM leads to amorphous framework (a‐dCoM), iii) glass transition (Tg = 566 K) to super‐cooled liquid (scl‐dCoM, spanning 38 K), iv) obtaining MOF glass g‐dCoM upon quenching the super‐cooled liquid, and v) re‐crystallization of super‐cooled liquid to six‐fold interpenetrated dia‐net framework [Co(pybz)2]6n (rec‐dCoM) under heating above 604 K. The access to glass from CoM, provides a new self‐perturbation strategy to create more MOF glasses without melting. The wider pore size distribution in amorphous/glassy MOFs than crystalline precursor realized the first time selective hydrocarbon gas separation by breakthrough experiments, which bring efficient separation of 1:99 C2H2/C2H4 by either a‐dCoM or g‐dCoM and produce polymer grade C2H4 with purity ≥ 99.5% after a single adsorption process. Furthermore, the mixture of 50:50 C3H6/C3H8 can be separated by a‐dCoM.