Fine Tuning and Specific Binding Sites with a Porous Hydrogen-Bonded Metal-Complex Framework for Gas Selective Separations

Research on hydrogen-bonded
organic frameworks (HOFs) has been
developed for quite a long time; however, those with both established
permanent porosities and functional properties are extremely rare
due to weak hydrogen-bonding interactions among molecular organic
linkers, which are much more fragile and difficult to stabilize. Herein,
through judiciously combining the superiority of both the moderately
stable coordination bonds in metal–organic frameworks and hydrogen
bonds, we have realized a microporous hydrogen-bonded metal-complex
or metallotecton framework HOF-21, which not only shows permanent
porosity, but also exhibits highly selective separation performance
of C2H2/C2H4 at room temperature.
The outstanding separation performance can be ascribed to sieving
effect confined by the fine-tuning pores and the superimposed hydrogen-bonding
interaction between C2H2 and SiF62– on both ends as validated by both modeling and
neutron powder diffraction experiments. More importantly, the collapsed
HOF-21 can be restored by simply immersing it into water or salt solution.
To the best of our knowledge, such extraordinary water stability and
restorability of HOF-21 were observed for the first time in HOFs,
underlying the bright perspective of such new HOF materials for their
industrial usage.