"We suggest that the noble themes in chemistry are there, but may be a little harder to see. One can look outward to the universe, or inward to the mind, and recognize the complexity and profundity of the questions to be answered. The problems that contemporary chemistry tackles are just as fundamental, but may not be as immediately obvious to the non-chemist. We could illustrate this claim in many ways, but perhaps one has received the broadest sustained attention: photosynthesis. How can light be harvested and converted to electrochemical energy that is sent off so efficiently in two directions: to both reductively generate the building blocks of life from carbon dioxide and oxidize water to oxygen? This extraordinarily complex question, to be sure, is closely linked to aspects of both physics (but cannot be completely reduced to physics) and biology; but the answer clearly lies in the realm of chemistry. And the workings of each individual component, as well as the entire integrated system that nature has constructed, pose questions that are fully as deep and inspirational as those in any other field of science. Moreover, on the practical side, the answers will be needed to devise methods for making comparably effective use of solar power, which at present appears to be the only resource of sufficient magnitude to cope with the world’s long-term energy needs."
Photosynthesis is indeed a hard, rewarding unsolved problem but I am disappointed that the authors did not instead pick the origin of life as the one shining chemical puzzle of all time. If you really had to pick one problem that's as important as the truly big problems in cosmology or biology, you would pick the origin of life. It is of enduring value to working chemists and it is easier to pitch to the public as a profound philosophical conundrum compared to photosynthesis. And the origin of life has the additional advantage that unlike photosynthesis, it probably cannot be solved even in principle, adding to the mystery and the everlasting allure.