  Covalent organic frameworks (COFs) have recently emerged as a new generation
of porous polymers combining molecular functionality with the robustness and
structural definition of crystalline solids. Drawing on the recent development
of tailor-made semiconducting COFs, we here report on a new COF capable of
visible-light driven hydrogen generation. The COF is based on hydrazone-linked
functionalized triazine and phenyl building blocks and adopts a layered
structure with a honeycomb-type lattice featuring mesopores of 3.8 nm and the
highest surface area among all hydrazone-based COFs reported to date. When
illuminated with visible light, the COF continuously produces hydrogen from
water without signs of degradation. With their precise molecular organization
and modular structure combined with high porosity, photoactive COFs represent
well-defined model systems to study and adjust the molecular entities central
to the photocatalyic process.
