Reticular-Chemistry-Inspired Supramolecule Design as a Tool to Achieve Efficient Photocatalysts for CO₂ Reduction

Abstract

Photocatalytic CO2 reduction into C1 products is one of the most trending research subjects of current times as sustainable energy generation is the utmost need of the hour. In this review, we have tried to comprehensively summarize the potential of supramolecule-based photocatalysts for CO2 reduction into C1 compounds. At the outset, we have thrown light on the inert nature of gaseous CO2 and the various challenges researchers are facing in its reduction. The evolution of photocatalysts used for CO2 reduction, from heterogeneous catalysis to supramolecule-based molecular catalysis, and subsequent semiconductor–supramolecule hybrid catalysis has been thoroughly discussed. Since CO2 is thermodynamically a very stable molecule, a huge reduction potential is required to undergo its one- or multielectron reduction. For this reason, various supramolecule photocatalysts were designed involving a photosensitizer unit and a catalyst unit connected by a linker. Later on, solid semiconductor support was also introduced in this supramolecule system to achieve enhanced durability, structural compactness, enhanced charge mobility, and extra overpotential for CO2 reduction. Reticular chemistry is seen to play a pivotal role as it allows bringing all of the positive features together from various components of this hybrid semiconductor–supramolecule photocatalyst system. Thus, here in this review, we have discussed the selection and role of various components, viz. the photosensitizer component, the catalyst component, the linker, the semiconductor support, the anchoring ligands, and the peripheral ligands for the design of highly performing CO2 reduction photocatalysts. The selection and role of various sacrificial electron donors have also been highlighted. This review is aimed to help researchers reach an understanding that may translate into the development of excellent CO2 reduction photocatalysts that are operational under visible light and possess superior activity, efficiency, and selectivity.

Applications of nanotechnology in smart textile industry: A critical review

“…The annual capacity of solar energy globally is 1575-49837 exajoules (EJ), which is almost three times higher than the total global consumption of 600 EJ [253] . Various kinds of inorganic semiconductor metal derivatives and their hybrid nanocomposites have been exploited to harness solar energy for various functions such as self-cleaning and energy generation [254] , [255] , [256] , [257] , [258] . Harifi and co-workers [259] developed lightweight, flexible and highly durable polyester fabric using TiO 2 /Fe 3 O 4 /Ag nano-photocatalysts for photo-transformation.…”

Photocatalytic Systems for CO2 Reduction: Metal-Complex Photocatalysts and Their Hybrids with Photofunctional Solid Materials

“…In the mixed systems of a photosensitizer and catalyst, the electron transfer from the OERS of the photosensitizer to the catalyst is limited by diffusion collisions between them. To accelerate electron transfer and improve photocatalytic activity, multinuclear metal complexes consisting of photosensitizer and catalyst have been developed; these are referred to as “supramolecular photocatalysts” . In 2005, we reported the successful supramolecular photocatalysts for CO 2 reduction for the first time .…”

A Small Organic Molecular Catalyst with Efficient Electron Accumulation for Near‐unity CO2 Photoreduction

“…[7][8][9][10] To achieve efficient CO 2 photoreduction, accumulation of reducing equivalents or electrons in molecular catalysts is vital since the reduction of CO 2 basically requires 2-8 electrons. [11] Transition metal complexes are proved to be highly suitable for this purpose, and therefore most molecular photocatalysts in CO 2 RR are based on transition metal complexes composed of metal centers and organic ligands. Metal centers can not only provide electrons for CO 2 reduction at their low oxidation states but also serve as coordination sites with CO 2 , while organic ligands are mainly used to support metal centers.…”

“…Molecular catalysts are intensively studied and have shown significant applications in homogeneous and heterogeneous photocatalysis [7–10] . To achieve efficient CO 2 photoreduction, accumulation of reducing equivalents or electrons in molecular catalysts is vital since the reduction of CO 2 basically requires 2–8 electrons [11] . Transition metal complexes are proved to be highly suitable for this purpose, and therefore most molecular photocatalysts in CO 2 RR are based on transition metal complexes composed of metal centers and organic ligands.…”