Abstract
We demonstrate photocatalytic hydrogen evolution using COF photosensitizers with molecular proton reduction catalysts for the first time. With azine-linked N2-COF photosensitizer, chloro(pyridine)cobaloxime co-catalyst, and TEOA donor, H2 evolution rate of 782 μmol h–1 g–1 and TON of 54.4 has been obtained in a water/acetonitrile mixture. PXRD, solid-state spectroscopy, EM analysis, and quantum-chemical calculations suggest an outer sphere electron transfer from the COF to the co-catalyst which subsequently follows a monometallic pathway of H2 generation from the CoIII-hydride and/or CoII-hydride species.
Highlights
With fossil fuel reserves dwindling every day, there is an urgent need for clean and sustainable alternative energy sources
We demonstrate photocatalytic hydrogen evolution using covalent organic frameworks (COFs) photosensitizers with molecular proton reduction catalysts for the first time
They feature low overpotentials for H2 generation, easy synthesis, and oxygen tolerance, and can be incorporated covalently into natural and artificial photocatalytic systems.[14−16] Cobaloximes have been used as earth abundant molecular H2 evolution co-catalysts, e.g., with MOF17 and carbon nitride photosensitizers.[18,19]
Summary
With fossil fuel reserves dwindling every day, there is an urgent need for clean and sustainable alternative energy sources. Efficient hydrogen evolution is seen with an azine-linked COF (N2) and a chloro(pyridine)cobaloxime co-catalyst (Co-1) in the presence of triethanolamine (TEOA) as a sacrificial electron donor in a water/acetonitrile mixture under AM 1.5 illumination. The filtered, washed, and recovered N2COF sample after photocatalysis does not produce any H2 in the presence of TEOA without Co-1, all other conditions being exactly the same as before These results combined prove beyond doubt that (i) Co-1 rather than the photochemically decomposed metallic cobalt is the catalytically active species and (ii) that it does not chemically interact with N2-COF. Photoluminescence lifetimes recorded using time-correlated single-photon counting method (TCSPC), show almost no change in the decay of N2-COF in the presence of either TEOA, Co-1 or both (Figure S23 and Table S8), which probably suggests a different time scale of the electron transfer process from TEOA and to Co-1 under these conditions.[53]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
