Hidden porous boron nitride as a high-efficiency membrane for hydrogen purification.

Nanoporous atom-thick two-dimensional materials with uniform pore size distribution and excellent mechanical strength have been considered as the ideal membranes for hydrogen purification. Here, our first-principles structure search has unravelled four porous boron nitride monolayers (m-BN, t-BN, h'-BN and h''-BN) that are metastable relative to h-BN. Especially, h'-BN consisting of B6N6 rings exhibits outstanding selectivity and permeability for hydrogen purification, higher than those of common membranes. Importantly, h'-BN possesses the mechanical strength to sustain a stress of 48 GPa, which is two orders of magnitude higher than that (0.38 GPa) of a recently reported graphene-nanomesh/single-walled carbon nanotube network hybrid membrane. The excellent selectivity, permeability and mechanical strength make h'-BN an ideal candidate for hydrogen purification.