Bent Alkyne Units as Active Sites: Structure–Activity Correlation in Graphdiyne-Inspired Polymers for Photocatalytic Hydrogen Evolution

Abstract

Alkyne bonds are promising for photoelectrocatalysis due to their tunable electronic structure; however, the relationship between their local geometry and photocatalytic function remains unclear. Herein, a graphdiyne-derived polymer featuring curved butadiyne linkages (PTEP) was designed and synthesized, and its photocatalytic performance was compared with a linear analogue (PDEB) to elucidate the effect of alkyne bending on hydrogen evolution. PTEP exhibits broad visible-light absorption, suitable band edges, and efficient charge separation, achieving a high H₂ evolution rate of >2250 μmol·g⁻¹·h⁻¹ with an 14.75% quantum efficiency at 420 nm, while PDEB shows negligible activity. Density functional theory calculations confirm the bent alkyne carbons in PTEP as the dominant active sites with a lower hydrogen adsorption free energy (–0.09 eV). This work demonstrates that geometric control of alkyne bonds can simultaneously modulate the band structure and expose highly active sites, providing clear structure–activity guidance for designing efficient alkyne-based photocatalysts.