Steric hindrance regulation in hydrogen-bonded organic frameworks: from nonporous to microporous

Steric hindrance regulation is key for adjusting the pore environment of crystalline porous materials, yet few cases show notable structural changes affecting porosity in hydrogen-bonded organic frameworks (HOFs). Herein, we report two HOFs, UPC-HOF-15 and UPC-HOF-16, constructed with methyl- and methoxy-modified isoreticular tricarboxylic acids, respectively. Due to the distinct steric hindrance, UPC-HOF-15 with hydrogen-bonding between carboxyl groups in two peripheral phenyl rings is nonporous, whereas the hydrogen-bonding in microporous UPC-HOF-16 exists between carboxyl groups in the central phenyl ring and one peripheral phenyl ring, both leaving the remaining carboxyl group forming hydrogen-bonding with solvent molecules. In addition, UPC-HOF-16 exhibits potential for methane purification. This work can provide insights into the discovery of new HOFs via steric hindrance regulation, boosting the diversification of structures and functions.