Three-Component Donor−π–Acceptor Covalent–Organic Frameworks for Boosting Photocatalytic Hydrogen Evolution Two-dimensional covalent–organic frameworks (2D COFs) have recently emerged as great prospects for their applications as new photocatalytic platforms in solar-to-hydrogen conversion; nevertheless, their inefficient solar energy capture and fast charge recombination hinder the improvement of photocatalytic hydrogen production performance. Herein, two photoactive three-component donor−π–acc...