Solar light-driven fuel production from carbon dioxide using organic photocatalysts is a promising technique for sustainable energy sources. Band gap engineering in sustainable organic photocatalysts for improving efficiency and fulfilling the requirements is highly anticipated. Here, we present a new strategy to engineer the band gap in covalent organic framework (COF) photocatalysts by varying the push−pull electronic effect. To implement this strategy, we have designed and synthesized four different COFs using a tripodal amine 4,4′,4″-(1,3,5-triazine-2,4,6triyl)tris(([1,1′-biphenyl]-4-amine)) [Ttba] with 1,3,5-triformylbenzene (COF-1), 2,4,6-triformylphloroglucinol (COF-2), 2,4,6triformylphenol (COF-3), and 2,4,6-triformylresorcinol (COF-4). On varying the number of hydroxyl units in the aldehyde precursor, the resulting COFs allow the fine-tuning of their band gap and band edge positions and result in different morphologies with varying surface areas. The enhanced optical properties of COF-3 and COF-4 with very suitable band gaps of 2.02 and 1.95 eV, respectively, enable them to demonstrate a high-efficiency photobiocatalytic system for NADH photoregeneration and enhanced visible light-driven formic acid production at a rate of 226.3 μmol g −1 in 90 min. The triazine core enables efficient charge separation, while the hydroxyl groups induce an electronic push−pull effect, regulating their photocatalytic efficiency. The results demonstrated the morphology-guided enhanced surface area and dual keto−enol tautomerism-induced push−pull effect in asymmetrical charge distribution as key features in the fine-tuning of the photocatalysts.

The targeted synthesis of an efficient, visible light active, recyclable, freestanding covalent organic framework thin film photocatalyst for multi-facet photocatalysis is the essence of the proposed work. A simple, scalable,...

The conversion of CO2 to valuable solar fuels by means of solar energy using metal‐free flexible film photocatalysts is an appealing strategy. Here we demonstrate a three dimensional aromatic polymer (3DAP) derived from triptycene (TC) as a metal free, stable and highly efficient visible light responsive flexible film photocatalyst for selective solar fuel production from CO2. For this research work, the polymerization of TC by the Diels–Alder reaction is exploited for the first time as a new synthetic approach for the construction of three dimensional aromatic polymer photocatalyst. The visible‐light harvesting ability, band gap suitability, high Brunauer–Emmett–Teller (BET) surface area and electron transfer capability via interconnecting 3D chain of 3DAP contribute to the excellent performance of the film photocatalyst as evident from 91.09 % NADH regeneration and 225.12 μmol of formic acid production. This work provides important insights into the design of flexible polymer film photocatalyst for selective solar fuel formation from CO2 and is expected to trigger further interest in sustainable solar energy conversion applications such as tailorable and wearable devices.