Cascaded Compression of the Size Distribution of Nanopores in Monolayer Graphene

Abstract

Nanoporous graphene has shown great promise for membrane separations. Its atomic thickness, remarkable mechanical, chemical, and thermal robustness could enable ultrahigh-flux membrane processes addressing persistent challenges in a wide range of separation needs. On the other hand, molecular separations across nanoporous graphene rely dominantly on size-based mechanisms (e.g, size exclusion) that is highly sensitive to the nanopore size and size distribution of nanopore ensemble created on the graphene. However, among existing nanopore creation methods, the process of nanopore nucleation is often coupled with nanopore expansion, which results in a lognormal nanopore size distribution with a long tail. It remains a challenge to obtain both high density and narrow size distribution of nanopores in graphene. Here, we report a cascaded compression approach to engineering nanopores in monolayer graphene for molecular separations with the assistance of electrical control of chemical vapor deposition of graphene[1]. The formation of nanopores is split into many small steps, in each of which the size distribution of all the existing nanopores is compressed by a combination of shrinkage and expansion, and at the same time of expansion, a new batch of nanopores is created, leading to increased nanopore density by each cycle. As a result, high-density nanopores with a short-tail size distribution are obtained by the cascaded compression that show high rejection and ultrafast organic solvent nanofiltration exceeding the state-of-the-art.Reference[1] Wang J, Park J H, Lu A Y, et al. Electrical Control of Chemical Vapor Deposition of Graphene. Journal of the American Chemical Society, 20