Self-Assembly of 2D Host-Guest Pore Networks via Entropy Compartmentalization

On the atomic scale, open host–guest (HG) structures (where one guest atom or molecule is enveloped by a cage of host atoms) are common. Zeolites are one example where a porous host structure traps and orients guest molecules. To instead use HG mechanisms on the colloidal scale to assemble useful structures for applications like photonics and particle adsorption, a deeper understanding of why HG structures assemble is needed. In this work, we show that athermal binary mixtures of simple concave star particles and convex polygon guest particles form HG networks. We show the reason for this assembly is due to entropy compartmentalization. In these systems the host particles are orientationally locked and trade a decrease in entropy to increase the entropy of the guest particles which rotate freely, thereby maximizing the system entropy. We also show that these pore networks are robust to small perturbations of the host shape, and that adsorption of hard polygons onto the porous 2D host network follows classical adsorption theory. Our results elucidate the thermodynamics of host-guest systems that are robust to shape perturbation and can be used in hard particle adsorption onto the 2D surface.