scholarly journals Photocatalytic CO2 reduction with a quantum efficiency exceeding 60%: time-resolved spectroscopic and X-ray studies on Cu(I) photosensitizers in coordinative interaction with Co(II) phthalocyanine catalysts

Author(s):  
Jia-Wei Wang ◽  
Xian Zhang ◽  
Michael Karnahl ◽  
Zhi-Mei Luo ◽  
Zizi Li ◽  
...  

Abstract The utilization of a fully noble-metal-free system for photocatalytic CO2 reduction remains a fundamental challenge, demanding the precise design of photosensitizers and catalysts, as well as the exploitation of their intermolecular interactions to facilitate electron delivery. Herein, we have implemented triple modulations on catalyst, photosensitizer and coordinative interaction between them for high-performance light-driven CO2 reduction. In this study, heteroleptic copper and cobalt phthalocyanine complexes were selected as photosensitizers and catalysts, respectively. An over ten-fold improvement in light-driven reduction of CO2 to CO is achieved for the catalysts with appending electron-withdrawing substituents for optimal CO-desorption ability. In addition, pyridine substituents were implanted at the backbone of the phenanthroline moiety of the Cu(I) photosensitizers and the effect of their axial coordinative interaction with the catalyst was tested. The combined results of 1H NMR titration experiment, steady-state/transient photoluminescence, and transient absorption spectroscopy confirm the coordinative interaction and reductive quenching pathway in photocatalysis corroboratively. It has been found that the catalytic performances of the coordinatively interacted systems are unexpectedly reverse to those with the pyridine-free Cu(I) photosensitizers. Moreover, the latter system enables a very high quantum efficiency up to 63.5% at 425 nm with a high selectivity exceeding 99% for CO2-to-CO conversion. As determined by time-resolved X-ray absorption spectroscopy and DFT calculation, the replacement of phenyl by pyridyl groups in the Cu(I) photosensitizer favors a stronger flattening and larger torsional angle change of the overall excited state geometry upon photoexcitation, which explains the decreased lifetime of the triplet excited state. Our work promotes the systematic multi-pathway optimizations on the catalyst, photosensitizer and their interactions for advanced CO2 photoreduction.

2021 ◽  
Vol 23 (5) ◽  
pp. 3656-3667
Author(s):  
Lucía Velasco ◽  
Leonel Llanos ◽  
Pedro Levín ◽  
Andrés Vega ◽  
Jin Yu ◽  
...  

Three homoleptic Cu(i) dimeric photosensitizers are studied through ultrafast X-ray and optical absorption spectroscopy. The complexes show distinct excited state lifetimes, due to the solvent type and spacers' flexibilities between the Cu centres.


2010 ◽  
Vol 114 (48) ◽  
pp. 12780-12787 ◽  
Author(s):  
Jenny V. Lockard ◽  
Aaron A. Rachford ◽  
Grigory Smolentsev ◽  
Andrew B. Stickrath ◽  
Xianghuai Wang ◽  
...  

Author(s):  
Matthew R. Ross ◽  
Benjamin E Van Kuiken ◽  
Matthew L. Strader ◽  
Hana Cho ◽  
Amy Cordones-Hahn ◽  
...  

Author(s):  
Lin X. Chen ◽  
Xiaoyi Zhang ◽  
Jenny V. Lockard ◽  
Andrew B. Stickrath ◽  
Klaus Attenkofer ◽  
...  

Transient molecular structures along chemical reaction pathways are important for predicting molecular reactivity, understanding reaction mechanisms, as well as controlling reaction pathways. During the past decade, X-ray transient absorption spectroscopy (XTA, or LITR-XAS, laser-initiated X-ray absorption spectroscopy), analogous to the commonly used optical transient absorption spectroscopy, has been developed. XTA uses a laser pulse to trigger a fundamental chemical process, and an X-ray pulse(s) to probe transient structures as a function of the time delay between the pump and probe pulses. Using X-ray pulses with high photon flux from synchrotron sources, transient electronic and molecular structures of metal complexes have been studied in disordered media from homogeneous solutions to heterogeneous solution–solid interfaces. Several examples from the studies at the Advanced Photon Source in Argonne National Laboratory are summarized, including excited-state metalloporphyrins, metal-to-ligand charge transfer (MLCT) states of transition metal complexes, and charge transfer states of metal complexes at the interface with semiconductor nanoparticles. Recent developments of the method are briefly described followed by a future prospective of XTA. It is envisioned that concurrent developments in X-ray free-electron lasers and synchrotron X-ray facilities as well as other table-top laser-driven femtosecond X-ray sources will make many breakthroughs and realise dreams of visualizing molecular movies and snapshots, which ultimately enable chemical reaction pathways to be controlled.


2009 ◽  
Vol 80 (12) ◽  
Author(s):  
P. W. Hillyard ◽  
S. V. N. T. Kuchibhatla ◽  
T. E. Glover ◽  
M. P. Hertlein ◽  
N. Huse ◽  
...  

Author(s):  
Jungkweon Choi ◽  
Mina Ahn ◽  
Jae Hyuk Lee ◽  
Doo-Sik Ahn ◽  
Hosung Ki ◽  
...  

The experimental and calculation results demonstrate that the 3MLppzCT state generated by the spin-forbidden transition rapidly relaxes to 3MLppyCT through internal conversion process with a time constant of ∼450 fs.


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