Thiazolo[5,4-d]thiazole-Based Donor-Acceptor Covalent Organic Frameworks for Sunlight-Driven Hydrogen Evolution.

2D covalent organic frameworks (COFs) could have well-defined arrangements of photo- and electro-active units that serve as electron or hole transport channels for solar energy harvesting and conversion, but their insufficient charge transfer and rapid charge recombination impede the sunlight-driven photocatalytic performance. We report a new donor-acceptor (D-A) system, PyTz-COF that was constructed from the electron-rich pyrene (Py) and electron-deficient thiazolo[5,4-d]thiazole (Tz). With its bicontinuous heterojunction, PyTz-COF demonstrated exceptional optoelectronic properties, photocatalytic ability in superoxide anion radical-mediated coupling of (arylmethyl)amines and photoelectrochemical activity in sunlight-driven hydrogen evolution. Remarkably, PyTz-COF exhibited a photocurrent up to 100 mA cm-2 at 0.2 V vs. RHE and could reach a hydrogen evolution rate of 2072.4 mmol g-1 h-1. This work is paving the way for reticular design of highly efficient and highly active D-A systems for solar energy harvesting and conversion.