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Photochemical Electrocyclic Reactions: Stereochemistry

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The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
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Updated: Apr 17, 2026

Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions

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Published on: October 5, 2019

Tunable organic photocatalysts for visible-light-driven hydrogen evolution.

Reiner Sebastian Sprick¹, Jia-Xing Jiang, Baltasar Bonillo

¹Department of Chemistry and Centre for Materials Discovery, The University of Liverpool , Crown Street, Liverpool L69 7ZD, United Kingdom.

Journal of the American Chemical Society

|February 4, 2015

Summary

Researchers developed novel amorphous organic polymers for efficient photocatalytic hydrogen production. These materials effectively utilize visible light, overcoming limitations of traditional ultraviolet-dependent catalysts for a cleaner fuel source.

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Published on: August 7, 2018

Area of Science:

Materials Science
Photocatalysis
Renewable Energy

Background:

Photocatalytic hydrogen production from water is a promising clean energy technology.
Current photocatalysts often rely on ultraviolet light, which is inefficiently utilized from the solar spectrum.
Crystalline photocatalysts have limited tunability in their light absorption properties.

Purpose of the Study:

To develop novel photocatalysts for hydrogen production that effectively utilize the solar spectrum.
To synthesize amorphous, microporous organic polymers with tunable optical gaps.
To investigate the photocatalytic activity of these polymers for hydrogen evolution from water.

Main Methods:

Synthesis of amorphous, microporous organic polymers with controlled optical gaps (1.94-2.95 eV).
Evaluation of polymer robustness and photocatalytic activity for hydrogen evolution.
Testing under visible light irradiation in the presence of a sacrificial electron donor.

Main Results:

Achieved exquisite synthetic control over the optical gap of the organic polymers.
Demonstrated that specific monomer compositions yield robust and effective photocatalysts.
Observed significant hydrogen evolution activity under visible light, without requiring a metal co-catalyst.

Conclusions:

Amorphous, microporous organic polymers can be designed as efficient photocatalysts for hydrogen production.
These novel materials exhibit visible-light photoactivity, addressing a key limitation of existing technologies.
The synthetic tunability offers a pathway to optimize photocatalysts for solar energy conversion.