Lewis acid-catalysed formation of two-dimensional phthalocyanine covalent organic frameworks

Covalent organic frameworks (COFs) offer a new strategy for assembling organic semiconductors into robust networks with atomic precision and long-range order. General methods for COF synthesis will allow complex building blocks to be incorporated into these emerging materials. Here we report a new Lewis acid-catalysed protocol to form boronate esters directly from protected catechols and arylboronic acids. This transformation also provides crystalline boronate ester-linked COFs from protected polyfunctional catechols and bis(boronic acids). Using this method, we prepared a new COF that features a square lattice composed of phthalocyanine macrocycles joined by phenylene bis(boronic acid) linkers. The phthalocyanines stack in an eclipsed fashion within the COF to form 2.3 nm pores that run parallel to the stacked chromophores. The material's broad absorbance over the solar spectrum, potential for efficient charge transport through the stacked phthalocyanines, good thermal stability and the modular nature of COF synthesis, show strong promise for applications in organic photovoltaic devices.