Hydrogen-Localization Transfer Regulation in 3D COFs Enhances Photocatalytic Acetylene Semi-Hydrogenation to Ethylene

In this work, a series of new crystalline three-dimensional covalent organic frameworks (3D COFs) based on [8+4] construction was designed and successfully realized efficient photocatalytic acetylene (C₂H₂) hydrogenation to ethylene (C₂H₄). By regulating the hydrogen-localization transfer effect in these 3D COFs, the Cz-Co-COF-H containing cobalt glyoximate active centers exhibited excellent C₂H₂-to-C₂H₄ performance, with an average C₂H₄ yield of 1755.33 μmol g^-1 h^-1 in pure C₂H₂, also showed near 100 % conversion of C₂H₂ in 1 % C₂H₂ contained crude C₂H₄ mixtures (industry-relevant conditions), and finally obtain polymer grade C₂H₄. In contrast, the Cz-Co-COF-BF₂ only showed one fifth activity due to lack of hydrogen-localization transfer. The density functional theory (DFT), projected density of states (PDOS) and molecular dynamics "slow-growth" kinetic calculations based on precise 3D COF structures confirmed that the rapid hydrogen species transfer, enhanced water dissociation and suitable C₂H₂ adsorption in COFs jointly contributed efficient photocatalytic acetylene hydrogenation (PAH). This work provides new opportunity towards rational design and development of crystalline photocatalysts for C₂H₂ hydrogenation.