A nanoporous two-dimensional polymer by single-crystal-to-single-crystal photopolymerization

Abstract

In contrast to the wide number and variety of available synthetic routes to conventional linear polymers, the synthesis of two-dimensional polymers and unambiguous proof of their structure remains a challenge. Two-dimensional polymers-single-layered polymers that form a tiling network in exactly two dimensions-have potential for use in nanoporous membranes and other applications. Here, we report the preparation of a fluorinated hydrocarbon two-dimensional polymer that can be exfoliated into single sheets, and its characterization by high-resolution single-crystal X-ray diffraction analysis. The procedure involves three steps: preorganization in a lamellar crystal of a rigid monomer bearing three photoreactive arms, photopolymerization of the crystalline monomers by [4 + 4] cycloaddition, and isolation of individual two-dimensional polymer sheets. This polymer is a molecularly thin (~1 nm) material that combines precisely defined monodisperse pores of ~9 Å with a high pore density of 3.3 × 10(13) pores cm(-2). Atomic-resolution single-crystal X-ray structures of the monomer, an intermediate dimer and the final crystalline two-dimensional polymer were obtained and prove the single-crystal-to-single-crystal nature and molecular precision of the two-dimensional photopolymerization.

Probing Carrier Transport and Structure-Property Relationship of Highly Ordered Organic Semiconductors at the Two-Dimensional Limit

“…These challenges may be alleviated if molecular crystals are processed into large-area, highly crystalline monolayers. Such 2D form factor will also bring about new applications such as nanoporous membranes and insulating dielectrics [12,13].Several recent breakthroughs in various types of 2D organic materials such as polymers [14,15], oligomers [16] and covalent organic frameworks [17] have already shown great promises along this direction. However, one of the most fundamental questions regarding the nature of charge transport at the 2D limit has not been addressed.…”

Interplay Between Mechanochemistry and Sonochemistry

“…If all-carbon graphene has so far attracted enormous attention in mass media, the fact that polymerized organic crystals can also be exfoliated to create two-dimensional sheets should likewise open a new age of innovation in materials design. The subject is in its infancy, but two recent papers in Nature Chemistry will pave the way for these exciting 2D-polymers [72,73]. Both studies exploit the photopolymerization of single crystals, in particular anthracene-based monomers, where photochemical dimerization is facilitated by aromatic unit stacking.…”

The plastics revolution: how chemists are pushing polymers to new limits

“…Using the same approach, Schlüter and Benjamin King, head of the chemistry department at the University of Nevada, Reno, have independently produced different types of 2D polymer 9,10 . Now collaborators, the two researchers hope that they will soon be able to make these sheets in kilogram batches, easily enough to distribute samples to research groups around the world.…”