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Covalent organic frameworks (COFs) are an emerging class of crystalline materials that are attracting increasing attention due to their high porosity, crystallinity, and tunable properties. Consequently, the strategic design of COF-based photocatalysts for various applications, including energy and environmental remediation, has attracted considerable interest. In particular, the sustainable production of clean fuel – hydrogen (H2) – by water splitting is a promising means to meet the global energy demand and to address the atmospheric CO2 concentration caused by the excessive use of fossil fuels. In this regard, COFs offer potential advantages due to their modular nature, which facilitates their rational design from suitable organic building blocks to achieve optimal properties of visible light harvesting properties and easy charge transport. As a result, extensive research has been devoted to the design of photoresponsive COFs for efficient water splitting to generate hydrogen. Here, we provide a comprehensive review of recent developments in the strategic design of COF-based photocatalysts for solar fuel production via water splitting. The various organic linkers used in the construction of photocatalytic COFs and their structure–property correlations are discussed in detail. The role of bandgap engineering in tuning the hydrogen evolution efficiency of COFs is also discussed. Furthermore, the current challenges and future perspectives of COF-based solid catalysts for green and sustainable clean fuel production are presented. Indeed, this review demonstrates the importance of COF-based photocatalysts for the visible-light-driven hydrogen evolution reaction (HER) and can be beneficial for the future design of photocatalytic systems. [ABSTRACT FROM AUTHOR]

C24H29NO7S, triclinic, P1 (no. 1) , a = 6.5903(3) Å, b = 9.7193(5) Å, c = 9.9874(4) Å, α = 82.462(4)°, β = 77.197(3)°, γ = 85.6180(4)°,V = 617.7 Å3, Z = 1, Rgt(F) = 0.0351, wRref(F2) = 0.0967, T = 123 K.

A new methodology for the pH‐triggered degradation of polymers or for the release of drugs under visible light irradiation based on the cyclization of ortho‐hydroxy‐cinnamates (oHC) to coumarins is described. The key oHC structural motif can be readily incorporated into the rational design of novel photocleavable polymers via click chemistry. This main‐chain moiety undergoes a fast photocleavage when irradiated with 455 nm light provided that a suitable base is added. A series of polyethylene glycol‐alt‐ortho‐hydroxy cinnamate (polyethylene glycol (PEG)n‐alt‐oHC)‐based polymers are synthesized and the time‐dependent visible‐light initiated cleavage of the photoactive monomer and polymer is investigated in solution by a variety of spectroscopic and chromatographic techniques. The photo‐degradation behavior of the water‐soluble poly(PEG2000‐alt‐oHC) is investigated within a broad pH range (pH = 2.1–11.8), demonstrating fast degradation at pH 11.8, while the stability of the polymer is greatly enhanced at pH 2.1. Moreover, the neat polymer shows long‐term stability under daylight conditions, thus allowing its storage without special precautions. In addition, two water‐soluble PEG‐based drug‐carrier molecules (mPEG2000‐oHC‐benzhydrol/phenol) are synthesized and used for drug delivery studies, monitoring the process by UV–vis spectroscopy in an ON/OFF intermittent manner. [ABSTRACT FROM AUTHOR]