Covalent Organic Framework and Carbon Nitride Composite for Scalable Solar Reforming.

Abstract

Solar reforming uses sunlight to valorize waste and offers a promising route to circular chemistry, but most current systems operate under corrosive conditions, lack scalability and processability, or suffer from poor selectivity in oxidative waste valorization. Here, a modular composite photocatalyst, comprising a crystalline covalent organic framework (COF), cyanamide-functionalized carbon nitride (CNx), indium tin oxide (ITO), and a nickel-based molecular catalyst (NiME), capable of driving selective waste valorization and H2 generation using visible light under pH neutral aqueous conditions is reported. The porous structure of the COF provides nanoconfinement, thereby supporting the targeted oxidation of polyols and sugars into formate (HCOO-), while carbon nitride in the presence of the molecular catalyst facilitates H2 evolution. ITO functions as a solid-state electron mediator, enabling coupled oxidative and reductive processes for the concurrent solar-driven production of H2 and HCOO-. The high processability of the COF|ITO|CNx|NiME composite allows for the construction of a standalone photoleaf and photopanel, which have been integrated into a single-window and a scalable multi-window reactor, respectively. Continuous operability over seven days, along with testing under outdoor conditions with pretreated plastic under direct sunlight, offers a pathway toward practical and scalable solar reforming using structurally tunable organic semiconductor composites.