Mechanochemistry enables rapid access to boron imidazolate frameworks (BIFs), including ultralight materials based on Li and Cu(I) nodes, as well as new and previously unexplored systems based on Ag(I) nodes. Compared to solution methods, mechanochemistry is faster, provides materials with improved porosity, and replaces harsh reactants (e.g. n-butyllithium) with simpler and safer oxides, carbonates or hydroxides. Periodic density-functional theory (DFT) calculations on polymorphic pairs of BIFs based on Li<sup…