A reflection on ‘A hydrazone-based covalent organic framework for photocatalytic hydrogen production’: teaching sponges new tricks

Covalent organic frameworks (COFs) are a unique class of porous materials built entirely from organic building blocks. As such, COFs unite the tunability of molecules with the robustness and optoelectronic functionality of extended solids-key requisites for (photo)catalysis. This LEGO®-like design of crystalline "molecular sponges" has captivated the imagination of chemists and inspired the first COF photocatalyst: a hydrazone-linked COF capable of harnessing visible light to drive the evolution of hydrogen from water. This commentary revisits that seminal contribution, published 11 years ago in Chemical Science (L. Stegbauer, K. Schwinghammer, B. V. Lotsch, Chem. Sci., 2014, 5, 2789-2793, https://doi.org/10.1039/C4SC00016A), and reflects on its lasting impact. We survey the major advances that have shaped COF photocatalysis over the past decade and outline emerging opportunities and challenges, offering a forward-looking perspective on the role of COFs in solar energy conversion.