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

Abstract

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., K 2 Cr 2 O 7 and LiAlH 4 ) 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 CO 2 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.

Direct Z-Scheme Photocatalytic System: Insights into the Formative Factors of Photogenerated Carriers Transfer Channel from Ultrafast Dynamics

“…Photocatalysis technology has been considered as an attractive approach to overcome serious energy and environmental crises by utilizing inexhaustible solar energy to drive various chemical reactions, such as overall water splitting, carbon dioxide reduction, and various contaminations degradation. − Compared with single-component photocatalysts, the conventional type II heterojunction photocatalysts, consisting of two different semiconductors with the staggered band structure alignment, can efficiently improve the spatial separation of photogenerated electrons and holes (PEHs) to suppress the recombination of photogenerated carriers. − Unfortunately, the efficient separation of PEHs is at the expense of the redox ability of the photogenerated carriers. − Inspired by the natural photosynthesis of plants, the artificial Z-scheme heterojunction system not only boosts the separation of PEHs, but also preserves their strong redox properties, which can obviously enhance the photocatalytic performance. − …”

A review on ZnS-based photocatalysts for CO2 reduction in all-inorganic aqueous medium

“…For example, CO 2 RR photocatalysts could couple a stable oxygen evolution photocatalyst in a Z-scheme system. (ii) CO 2 reduction could couple with other reactions, such as photocatalytic organic reactions 62 or enzymatic reactions, to obtain high value-added products and enhance the overall CO 2 reduction efficiency. (iii) Nano-sized and quantum dot sulfides with high-density surface states could be a promising type of photocatalyst for CO 2 reduction.…”

Fluid Field Modulation in Mass Transfer for Efficient Photocatalysis

“…[ 1–15 ] In this context, more and more focuses were allocated to viable and robust technologies for generating green energy and thus substituting traditional fossil fuels. [ 16–32 ] For example, piezoelectric/triboelectric/pyroelectric nanogenerators, especially the recently invented magnetoelastic generators, [ 22,24–26 ] can scavenge surrounding renewable energy (such as human walking and running, heart beating, natural water flow, wind, environmental temperature variation, and so forth) to produce electricity for power supply or healthca, [ 33–52 ] electrocatalytic technology can undergo oxygen reduction and oxygen/hydrogen evolution reactions under bias voltage to yield clean energy, [ 53–60 ] and environment‐friendly batteries are developed and applied in electrochemical energy storage and conversions. [ 61–65 ] Notably, among these viable technologies, photocatalytic technology can convert inexhaustible solar energy into chemical energy, e.g., splitting water into green fuel hydrogen, reducing carbon dioxide into carbon oxide or methane, fixing nitrogen, degrading organic pollutions and antibiotics, and disinfecting bacteria and viruses, which shows greater potential in alleviating the global energy and environmental issues.…”

“…[ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ] In this context, more and more focuses were allocated to viable and robust technologies for generating green energy and thus substituting traditional fossil fuels. [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ] For example, piezoelectric/triboelectric/pyroelectric nanogenerators, especially the recently invented magnetoelastic generators, [ 22 , 24 , 25 , 26 ] can scavenge surrounding renewable energy (such as human walking and running, heart beating, natural water flow, wind, environmental temperature variation, and so forth) to produce electricity for power supply or healthca, [ 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , ...…”