Tunable covalent benzo-heterocyclic rings constructed using two-dimensional conjugated polymers for visible-light-driven water splitting.

Developing highly efficient, stable, and cost-effective two-dimensional (2D) conjugated polymers (CPs) for overall water splitting (OWS) is critical for producing clean and renewable hydrogen energy, yet it remains a great challenge. Here, we designed eight 2D CPs through the topological assembly of diacetylene and benzene-derived molecular linkers that can offer active sites for hydrogen and oxygen evolution reactions, and explored their structural, electronic, optical, and photocatalytic OWS properties by performing first-principles computations. It is shown that incorporating benzo-heterocyclic rings into CPs can significantly modulate the electronic structures of CPs and broaden the spectral absorption, suitable for visible-light-driven OWS. Remarkably, through a range of screening criteria, including stability, electronic band structures, band edge alignments, and photocatalytic activity, we found that CP-4 based on diacetylene and benzotrifuran can spontaneously trigger the OWS in a neutral environment under its own light-induced bias, eliminating the need for sacrificial agents or cocatalysts. Specifically, the HER active site is primarily located at diacetylene moieties, while the OER active site is mainly concentrated on the benzo-heterocyclic rings. Moreover, the ideal STH efficiency for OWS on CP-4 was estimated to be 13.87%, highlighting its potential as a prospective photocatalyst for large-scale industrial OWS. Our findings open a door to the rational design of novel polymer photocatalysts for OWS.