Identification of Prime Factors to Maximize the Photocatalytic Hydrogen Evolution of Covalent Organic Frameworks

Abstract

Visible light driven hydrogen (H₂) production from water is a promising strategy to convert and store solar energy as chemical energy. Covalent organic frameworks (COFs) are front runners among different classes of organic photocatalysts. Photocatalytic activity of COFs depends on numerous factors such as electronic band gap, crystallinity, surface area, exci-ton migration, stability of transient species, charge separation and transport, etc. However, it is challenging to fine tune all these factors simultaneously to enhance the photocatalytic activity. Hence, in this report, an effort has been made to understand the interplay of these factors and identify the key factors for efficient photocatalytic H₂ production through structure–property–activity relationship. Careful molecular engineering allowed us to optimize all the above plausible factors impacting on the overall catalytic activities of a series of isoreticular COFs. The present study determines three prime factors: light absorption, charge carrier generation, and their transport, which influence the photocatalytic H₂ production of COFs in much greater extent than the other factors.