Microporosity of a Guanidinium Organodisulfonate Hydrogen-Bonded Framework

Abstract

Guanidinium organosulfonates (GSs) are a large and well-explored archetypal family of hydrogen-bonded organic host frameworks that have, over the past 25 years, been regarded as nonporous. Reported here is the only example to date of a conventionally microporous GS host phase, namely guanidinium 1,4-benzenedisulfonate (p-G₂ BDS). p-G₂ BDS is obtained from its acetone solvate, AcMe@G₂ BDS, by single-crystal-to-single-crystal (SC-SC) desolvation, and exhibits a Type I low-temperature/pressure N₂ sorption isotherm (SA_BET =408.7(2) m² g^-1 , 77 K). SC-SC sorption of N₂ , CO₂ , Xe, and AcMe by p-G₂ BDS is explored under various conditions and X-ray diffraction provides a measurement of the high-pressure, room temperature Xe and CO₂ sorption isotherms. Though p-G₂ BDS is formally metastable relative to the "collapsed", nonporous polymorph, np-G₂ BDS, a sample of p-G₂ BDS survived for almost two decades under ambient conditions. np-G₂ BDS reverts to zCO₂ @p-G₂ BDS or yXe@p-G₂ BDS (y,z=variable) when pressure of CO₂ or Xe, respectively, is applied.

Keywords: gas sorption; guanidinium sulfonates; hydrogen-bonded organic frameworks; porosity; porous molecular solids.