https://phys.org/news/2019-01-defects-d-materials-amazing-properties.html

Now that problem has been solved by researchers at MIT, who have produced a catalog of the exact sizes and shapes of holes that would most likely be observed (as opposed to the many more that are theoretically possible) when a given number of atoms is removed from the atomic lattice. The results are described in the journal Nature Materials in a paper by graduate student Ananth Govind Rajan, professors of chemical engineering Daniel Blankschtein and Michael Strano, and four others at MIT, Lockheed Martin Space, and Oxford University.

"It's been a longstanding problem in the graphene field, what we call the isomer cataloging problem for nanopores," Strano says. For those who want to use graphene or similar two-dimensional, sheet-like materials for applications including chemical separation or filtration, he says, "we just need to understand the kinds of atomic defects that can occur," compared to the vastly larger number that are never seen.