Cation···π Anchoring Induced In Situ Growth for Constructing 2D Conjugated Polymer/MIS Heterojunctions Toward Efficient Photocatalytic Hydrogen Evolution

Constructing heterojunctions with intimate interfacial contact and efficient charge separation is crucial for boosting photocatalytic hydrogen evolution. Herein, we report a cation···π anchoring induced in situ growth strategy to precisely fabricate 2D/2D poly(3,4-dimethylthiophene-alt-4,7-dithienyl-2,1,3-benzothiadiazole)/magnesium indium sulfide (PDDB/MIS) heterojunctions for highly efficient photocatalytic hydrogen evolution. The 2D PDDB with alternating π/π-hole arrangement features abundant electron-rich π-sites, which can selectively anchor Mg2+/In3+ via stable cation···π interactions. These anchored metal cations act as uniform nucleation sites to induce the in situ growth of MIS on PDDB surface, achieving intimate interfacial contact. Density functional theory (DFT) calculations and comprehensive characterization results confirm that the orbital hybridization between S-p/C-p orbitals of PDDB and In-p/Mg-s/p orbitals of MIS effectively reduces the interfacial charge transfer barrier and enables efficient photogenerated carrier separation. The optimized 5PDDB/MIS exhibits excellent photocatalytic hydrogen evolution rate of 10.1 mmol h-1 g-1 under visible light irradiation, which is 18.0 and 9.7 times higher than those of MIS and PDDB, respectively. Furthermore, the high apparent quantum yield of 8.62% under 600 nm is obtained, outperforming most reported MIS-based photocatalysts. This work illustrates a universal interfacial engineering strategy for constructing 2D/2D heterojunction with efficient charge separation and offering insights for sustainable solar energy conversion.