Demonstrating Band Design in Two-Dimensional Covalent Organic Frameworks*

Two dimensional covalent organic frameworks (COFs) are periodic lattices whose rational design can yield novel optoelectronic properties and new heterostructure devices. Analogous to graphene and the inorganic family of 2D materials, 2D COFs are covalently bonded in-plane with out-of-plane bonding through Van der Waals interactions. To date, 2D COF properties are limited by large molecular bandgaps, low intermolecular coupling, and poor control of the material morphology. Here, we report the rational design and characterization of a new, highly conjugated, semiconducting 2D framework. We characterize the structure by X-ray scattering, TEM, and AFM, and demonstrate facile manipulation onto arbitrary experimental platforms. We further employ broadband optical and vibrational spectroscopies to observe electronic behavior emergent in this highly conjugated system.