Light-Mediated Sustainable Conversion of Carbon Dioxide to Valuable Methanol by Highly Efficient Covalent Organic Framework g‑C₃N₄ Composites as a Reusable Photocatalyst

A novel triazine-based structured two-dimensional (2D) covalent organic framework (COF), known as TRITER-1, has been prepared through the Schiff-base condensation reaction between terephthalaldehyde and 1,3,5-tris­(4-aminophenyl)­triazine. Additionally, g-C₃N₄ has been incorporated within imine-based covalent organic frameworks to produce the composite known as TRITER-1@g-C₃N₄, which has a relatively small band gap of 2.0 eV. This composite, called TRITER-1@g-C₃N₄, has been synthesized and effectively used toward the light-driven formation of methanol from the most greenhouse gas CO₂. This highly crystalline organic polymeric material demonstrated an outstanding photocatalytic activity. The active photocatalyst TRITER-1@g-C₃N₄ composite successfully reduces CO₂ into methanol under ambient reaction conditions in the presence of NiO nanoparticles as a cocatalyst under atmospheric pressure. The visible-light-accelerated metal-free CO₂ reduction into methanol by this COF composite has been accomplished under 15 W of a white LED light illumination, with a maximum turnover number of (TON = 172, μmol = 22 600). By varying the light intensity, it was clear that the reaction failed to take place in the absence of a white LED. We proved that sunlight can also produce a TON of around 73 under conditions that allow for sustainable reactions. This catalyst retains its catalytic function after being regenerated multiple times and is effective and selective.