Metalphthalocyanine frameworks grown on TiO 2 nanotubes for synergistically and efficiently electrocatalyzing urea production from CO 2 and nitrate

Electrocatalytic synthesis of urea from CO 2 and NO_3^ - under ambient conditions provides an appealing alternative to the traditional energy-intensive urea synthetic protocol. Highly active and selective electrocatalysts for efficient urea production are therefore urgently desired owing to the unsatisfactory performance of the thus far reported catalysts. Herein, a phthalocyanine-based (Pc-based) covalent organic framework (COF), namely CoPc-COF, fabricated from the nucleophilic substitution reaction of hexadecafluorophthalocyaninato cobalt with octahydroxylphthalocyanine cobalt, in situ grew on the surface of multilayered TiO 2 nanotubes (NTs), generating the CoPc-COF@TiO 2 NTs composite. Powder X-ray diffraction analysis in combination with electron microscopy measurements discloses the uniform coating of crystalline CoPc-COF on the multilayered TiO 2 NTs in CoPc-COF@TiO 2 NTs. Remarkably, electrochemical tests reveal the superior electrocatalytic activity of CoPc-COF@TiO 2 NTs towards urea production from CO 2 and NO_3^ - with a record-high yield of 1,205 µg h −1 cm −2 and an outstanding Faraday efficiency of 49