Post-Synthetic Modification of a Metal–Organic Framework Glass

Abstract

Melt-quenched metal−organic framework (MOF) glasses have gained significant interest as the first new category of glass reported in 50 years. In this work, an amine-functionalized zeolitic imidazolate framework (ZIF), denoted ZIF-UC-6, was prepared and demonstrated to undergo both melting and glass formation. The presence of an amine group resulted in a lower melting temperature compared to other ZIFs, while also allowing material properties to be tuned by post-synthetic modification (PSM). As a prototypical example, the ZIF glass surface was functionalized with octyl isocyanate, changing its behavior from hydrophilic to hydrophobic. PSM therefore provides a promising strategy for tuning the surface properties of MOF glasses.

Investigating the chemical sensitivity of melting in zeolitic imidazolate frameworks

“…5, S37, S38), with the strong colour of these crystals supporting the inclusion of abIm within the framework. 60 PXRD supported crystallisation in a zni topology framework, with a reasonable Pawley fit obtained using ZIF-zni as a starting model i.e., using the I4 1 cd space group (Fig. S39, Table S6).…”

“…We speculate that abIm lowers T m here by weaking the Zn-N coordination bonds in the framework, i.e., the enthalpic contribution to melting, in line with previous studies. 60 The amine functionality on abIm also has the potential to form hydrogen bonds during the melting process. These dispersive interactions may stabilise the uncoordinated linkers that form during melting, reducing the energy barrier to dissociation and hence lowering the melting temperature.…”

“…18 It has also recently been reported that post-synthetically modifying a ZIF resulted in a change in its surface water contact angle by over 30°, despite only a 1% change in its linker chemistry. 60 Here, we wanted to investigate the chemical sensitivity of melting in ZIFs further by achieving a level of chemical doping of less than 1%.…”

“…5-aminobenzimidazolate (abIm -C 7 H 6 N 3 − ) was chosen as the second linker as it was recently reported to significantly reduce the melting temperature in a cag topology ZIF. 60 Briefly, zinc nitrate hexahydrate, imidazole and 5-aminobenzimidazole were mixed in DEF before heating at 130 °C for 48 h (Fig. S36 †).…”

Transport tuning strategies in MOF film synthesis – a perspective

“…For example, halogenated and amino functionalised ZIF-62 glass particles showed interesting properties for gas separation, and possibly other separation processes. 17,119 The intracrystalline transport of MOF glass can also be tuned by post-synthetic modication strategies as experienced by the widely studied MOF crystals as discussed. MOF glasses are promising candidates to be further explored in thin lms and membranes mainly for separation processes.…”