Fully Conjugated Two-Dimensional sp(2)-Carbon Covalent Organic Frameworks as Artificial Photosystem I with High Efficiency

摘要

The synthesis of fully conjugated sp(2)-carbon covalent organic frameworks (COF) is extremely challenging given the difficulty of the formation of very stable carbon-carbon double bonds (-C=C-). Here, we report the successfid preparation of a 2D COF (TP-COF) based on triazine as central planar units bridged by sp(2)-carbon linkers through the -C=C-condensation reaction. High-resolution-transmission electron microscopy (HRTEM) clearly confirmed the tessellated hexagonal pore structure with a pore center-to-center distance of 2 nm. Powder X-ray diffraction (PXRD) together with structural simulations revealed an AA stacking mode of the obtained layered structure. TP-COF turned out to be an excellent semiconductor material with a LUMO energy of -3.23 eV and a band gap of 2.36 eV. Excitingly, this novel sp(2) carbon conjugated TP-COF exhibited unprecedented coenzyme regeneration efficiency and can significantly boost the coenzyme-assisted synthesis of L-glutamate to a record-breaking 97 % yield within 12 minutes.