Rational Synthesis of a Hierarchical Supramolecular Porous Material Created via Self-Assembly of Metal-Organic Framework Nanosheets.

ABSTRACT

Hierarchically porous materials with high stability and tailorable pore characters have potential for mass transfer applications, including bulky molecule capture and separation, heterogeneous catalysis, and drug delivery. The scope of functionalities can be notably broadened by employing metal-organic framework (MOF) sheets with tunable thickness as giant molecular building blocks for self-assembly into hierarchical supramolecular porous coordination materials. However, synthesizing MOF sheets with controllable bulkiness has proved challenging for scientists. We present a rational yet unprecedented bottom-up strategy to prepare a novel two-dimensional MOF sheet [Zn(BPDI)(Py)2] (BPDI = N,N'-bis(glycinyl)pyromellitic diimide; Py = pyridine) with unusual and highly desired tunable thickness. These sheets self-organize into a unique three-dimensional supramolecular coordination material (NEU-1) with tailorable porosity. To assess its technological relevance, NEU-1c is tested as a support of amine sorbent for CO2 capture. Multichannel porous NEU-1c solves the conventional trade-off suffered by supported amine carbon dioxide adsorbents between increasing amine content and decreasing access to amine sites. Our synthesis process opens the door to novel MOF nanosheets and unique hierarchical supramolecular porous materials with tailorable porosity.