Formation of Porosity toward Acetylene upon Vitrification of Non-porous Photochromic Coordination Polymer Crystals

Abstract

Designing permanent microporosity in a glassy state of coordination polymer (CP) and metal–organic framework (MOF) has been challenging due to densification of the structures upon vitrification. Here, we propose a new approach to create porosity in CP/MOF glasses derived from nonporous 1D crystal structures. Glassy states of two dense 1D crystal structures [Ag2(cis-dbe) (CF3SO3)2] and [Ag2(cis-dbe) (CF3CO2)2], where cis-dbe = cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene, were prepared by ball milling. Glass structures and dynamics were characterized by synchrotron X-ray, solid-state NMR, and thermal analyses. Loosened assembly of 1D chains through glass formation enabled representation of permanent microporosity and resulted in selective gas sorption behaviors of acetylene over CO2. It elucidated that the property of gas uptake is affected by the glass dynamics and interaction with anions. Reversible photochromism of cis-dbe is preserved in the glasses, leading to multi-functional glass materials.

Functional metal–organic liquids

“…Although melting and vitrification are common in many material families, they remain exotic within the context of CPs/MOFs since most tend to decompose upon heating due to the irreversible decomposition prior to reaching the T m . This led to the exploration of alternative methods that circumvent the need for melting, including mechanical vitrification, 68–72 direct synthesis, 73,74 and dehydration. 75,76 Since the first observation of stable liquid states 34 and vitrification, 31,54,67 examples of CPs/MOFs exhibiting crystal melting have recently expanded beyond d 10 metal ions to include a broader range of transition metals and a more comprehensive selection of linkers (Fig.…”