S-Scheme TpPa/C₆N₇ heterobilayer: conjugated microporous polymers/covalent organic frameworks-based photocatalyst for...

Materials based on conjugated microporous polymers (CMPs) and covalent organic frameworks (COFs) are promising for photocatalytic overall water splitting (OWS). However, their practical application is limited by inefficient separation of photogenerated electron-hole (e-h) pairs and the inherently challenging four-electron oxygen evolution reaction (OER). Herein, we propose a novel CMP/COF S-scheme heterobilayer comprising a TpPa monolayer (polycondensation product of 1,3,5-triformylphloroglucinol and p-phenylenediamine) and a C₆N₇ monolayer (heptazine analog of g-C₃N₄) to address these challenges. First-principles calculations and time-dependent nonadiabatic molecular dynamics simulations reveal that photogenerated carriers in the 2D/2D TpPa/C₆N₇ heterobilayer follow an S-scheme migration pathway, enabling rapid e-h separation as well as spatial separation of the hydrogen evolution reaction (HER) and OER active sites on the TpPa and C₆N₇ layers, respectively. The heterobilayer exhibits a suitable bandgap and energy levels for efficient visible-light absorption and provides strong driving forces (0.89 V for HER and 3.19 V for OER) for pure-water splitting without cocatalysts. Furthermore, the driving force allows dynamic balancing of HER and OER kinetics across a wide pH range (0-12.91), enhancing OWS performance. The predicted solar-to‑hydrogen (STH) energy conversion efficiency reaches 14.04 %, surpassing most single-component photocatalysts. This study provides new insights into constructing S-scheme heterostructures from CMPs/COFs and establishes a viable strategy for designing efficient solar-driven OWS photocatalytic systems.