Combustible ice mimicking behavior of hydrogen-bonded organic framework at ambient condition.

Adsorption of guest molecules by porous materials proceeds in a spontaneous exothermic way, whereas desorption usually requires external energy input as an endothermic process. Reducing such energy consumption makes great sense in practice. Here we report the reversible and automatic methanol (MeOH) adsorption/release in an ionic hydrogen-bonded organic framework (iHOF) constructed from guanidinium cation and borate anion ([B(OCH3)4]3[C(NH2)3]4Cl•4CH3OH, termed Gd-B) at ambient condition. The metastable Gd-B automatically releases all sixteen MeOH molecules (63.4 wt%) via desorption and tetra-methyl borate hydrolysis at ambient atmosphere and the structure can be recovered when re-exposed to MeOH vapor or liquid, mimicking combustible ice behavior but at ambient condition. Reversible capture/release of four guest MeOH molecules is also realized without destroying its crystal structure. The combustible Gd-B paves a way for exploring metastable iHOF materials as carrier for alternative energy source and drug delivery etc. Porous materials function as sorbents for gas storage but release of guest molecules often needs extra energy. Here the authors report reversible methanol adsorption and release in a hydrogen-bonded organic framework, which mimics combustible ice behavior but under ambient condition.