Control of selectivity in organic synthesis via heterogeneous photocatalysis under visible light

Organic synthesis driven by heterogeneous catalysis is a central research theme to both fundamental research and industrial production of fine chemicals. However, the employment of stoichiometric strong oxidizing or reducing reagents (e.g., K₂Cr₂O₇ and LiAlH₄) and harsh reaction conditions (e.g., high temperature and pressure) always leads to the products of overreaction and other by-product residues (e.g., salt and acid waste). Thus the poor control of product selectivity and tremendous energy consumption result in the urgent demand to develop novel technologies for heterogeneous catalysis. Given the current global theme of development in CO₂ reduction and sustainable energy utilization, one promising protocol is heterogeneous photocatalysis. It enables sustainable solar-to-chemical energy conversion under mild conditions (e.g., room temperature, ambient pressure, and air as the oxidant) and offers unique reaction pathways for improved selectivity control. To accurately tailor the selectivity of desired products, the electronic structure (e.g., positions of valence-band maximum and conduction-band minimum), geometric structure (e.g., nanorod, nanosheet, and porous morphology), and surface chemical micro-environment (e.g., vacancy sites and co-catalysts) of heterogeneous photocatalysts require rational design and construction. In this review, we will briefly analyze some effective photocatalytic systems with the excellent regulation ability of product selectivity in organic transformations (mainly oxidation and reduction types) under visible light irradiation, and put forward opinions on the optimal fabrication of nanostructured photocatalysts to realize selective organic synthesis.