Simulation of nanoporous carbons: A chemically constrained structure

Abstract

Nanoporous carbons (NPCs) are useful in adsorptive separations and catalysis, owing to their ability to discriminate between molecules on the basis of size and shape. This property arises from their narrow pore size distribution, which is typically centred at a size corresponding to 0.5 nm. Despite this level of nanoregularity. there is no long-range order within these materials. Structural coherence dissipates to extinction at distances longer than 1–1.2 nm. For this reason, these nanoporous materials are complex solids and offer an intriguing problem in structural simulation and modelling. We show that modelling the spatial complexity of NPCs can be overcome by their chemical simplicity. Recognizing that the structures are comprised of trigonal sp² carbon and imposing chemical and physical constraints on the possible outcomes of the simulation provide a means to surmounting the modelling problem presented by the intrinsic disorder. By this approach, models of the solid can be arrived at that match the density, hydrogen to carbon ratio and neutron diffraction patterns of actual NPCs quite well. Thus, by using chemical logic and experimentally grounded constraints, good three-dimensional structures for NPC can be obtained by simulation.