  The production of high-quality two-dimensional (2D) materials is essential
for the ultimate performance of single layers and their hybrids. Hexagonal
boron nitride (h-BN) is foreseen to become the key 2D hybrid and packaging
material since it is insulating, tight, flat, transparent and chemically inert,
though it is difficult to attain in ultimate quality. Here, a new scheme is
reported for producing single layer h-BN that shows higher quality and much
more uniformity than material from chemical vapor deposition (CVD). We
delaminate CVD h-BN from Rh(111) and transfer it to a clean metal surface. The
twisting angle between BN and the new substrate yields metastable moir\'e
structures. Annealing above 1000 K leads to 2D distillation, i.e.,
catalyst-assisted BN sublimation from the edges of the transferred layer and
subsequent condensation into superior quality h-BN. This provides a new and
low-cost way of high-quality 2D material production remote from CVD
instrumentation.
