  In recent years, experimental and theoretical investigations have shown that
anisotropic colloids can self-organise into ordered porous monolayers, where
the interplay of localised bonding sites, so called patches, with the
particle's shape is responsible for driving the systems away from close-packing
and towards porosity. Until now it has been assumed that patchy particles have
to be fully bonded with their neighbouring particles for crystals to form, and
that, if full bonding cannot be achieved due to the choice of patch placement,
disordered assemblies will form instead. In contrast, we show that by
deliberately displacing the patches such that full bonding is disfavored, a
different route to porous crystalline monolayers emerges, where geometric
frustration and partial bonding are pivotal in the structure formation process.
The resulting dangling bonds lead to the emergence of effectively chiral units
which then act as building blocks for energetically equivalent crystal
polymorphs.
