Shape engineering of a g-C3 N4 framework, with interconnecting nanosheets and highly open-up spherical surfaces with sharp edges, can easily accelerate charge separation and promote mass transfer for photoredox catalysis, achieving an apparent quantum yield of 9.6% at 420 nm in an assay of the photocatalytic hydrogen evolution reaction.

Construction of organic semiconducting materials with in-plane π-conjugated structures and robustness through carbon-carbon bond linkages, alternatively as organic graphene analogs, is extremely desired for powerfully optoelectrical conversion. However, the poor reversibility for sp 2 carbon bond forming reactions makes them unavailable for building high crystalline well-defined organic structures through a self-healing process, such as covalent organic frameworks (COFs). Here we report a scalable solution-processing approach to synthesize a family of two-dimensional (2D) COFs with trans -disubstituted C = C linkages via condensation reaction at arylmethyl carbon atoms on the basis of 3,5-dicyano-2,4,6-trimethylpyridine and linear/trigonal aldehyde (i.e., 4,4″-diformyl- p -terphenyl, 4,4′-diformyl-1,1′-biphenyl, or 1,3,5-tris(4-formylphenyl)benzene) monomers. Such sp 2 carbon-jointed-pyridinyl frameworks, featuring crystalline honeycomb-like structures with high surface areas, enable driving two half-reactions of water splitting separately under visible light irradiation, comparable to graphitic carbon nitride (g-C 3 N 4 ) derivatives.

The search for metal-free organic photocatalysts for H2 production from water using visible light remains a key challenge. Reported herein is a molecular structural design of pure organic photocatalysts, derived from conjugated polybenzothiadiazoles, for photocatalytic H2 evolution using visible light. By alternating the substitution position of the electron-withdrawing benzothiadizole unit on the phenyl unit as a comonomer, various polymers with either one- or three-dimensional structures were synthesized and the effect of the molecular structure on their catalytic activity was investigated. Photocatalytic H2 evolution efficiencies up to 116 μmol h(-1) were observed by employing the linear polymer based on a phenyl-benzothiadiazole alternating main chain, with an apparent quantum yield (AQY) of 4.01 % at 420 nm using triethanolamine as the sacrificial agent.

Single‐atom catalysts have drawn considerable attention because of their unique catalytic properties. However, the high surface energy of single atoms restricts their fabrication and creates significant challenges for further developments. In order to overcome this problem, metal organic framework (MOF)‐derived carbon materials can be served as ideal supports to anchor atomically dispersed metal atoms, due to their tunable particle size and shape features, by providing high surface area, porosity, thermal, and chemical stability. This review highlights the recent advances in i) different types of construction strategies for MOF‐derived carbon‐supported single‐atom catalysts, and ii) the catalytic applications of these MOF‐derived carbon‐supported single‐atom catalysts. Further, this review offers a valuable insight into the current challenges and future opportunities for MOF‐derived carbon‐supported single‐atom catalysts.

Polymeric carbon nitride modified with selected heteroatom dopants was prepared and used as a model photocatalyst to identify and understand the key mechanisms required for efficient photoproduction of H2O2 via selective oxygen reduction reaction (ORR). The photochemical production of H2O2 was achieved at a millimolar level per hour under visible‐light irradiation along with 100 % apparent quantum yield (in 360–450 nm region) and 96 % selectivity in an electrochemical system (0.1 V vs. RHE). Spectroscopic analysis in spatiotemporal resolution and theoretical calculations revealed that the synergistic association of alkali and sulfur dopants in the polymeric matrix promoted the interlayer charge separation and polarization of trapped electrons for preferable oxygen capture and reduction in ORR kinetics. This work highlights the key features that are responsible for controlling the photocatalytic activity and selectivity toward the two‐electron ORR, which should be the basis of further development of solar H2O2 production.

The polarity of a semiconducting molecule affects its intrinsic photophysical properties, which can be tuned by varying the molecular geometry. Herein, we developed a D3h‐symmetric tricyanomesitylene as a new monomer which could be reticulated into a vinylene‐linked covalent organic framework (g‐C54N6‐COF) via Knoevenagel condensation with another D3h‐symmetric monomer 2,4,6‐tris(4′‐formyl‐biphenyl‐4‐yl)‐1,3,5‐triazine. Replacing tricyanomesitylene with a C2v‐symmetric 3,5‐dicyano‐2,4,6‐trimethylpyridine gave a less‐symmetric vinylene‐linked COF (g‐C52N6‐COF). The octupolar conjugated characters of g‐C54N6‐COF were reflected in its scarce solvatochromic effects either in ground or excited states, and endowed it with more promising semiconducting behavior as compared with g‐C52N6‐COF, such as enhanced light‐harvesting and excellent photo‐induced charge generation and separation. Along with the matched energy level, g‐C54N6‐COF enabled the two‐half reactions of photocatalytic water splitting with an average O2 evolution rate of 51.0 μmol h−1 g−1 and H2 evolution rate of 2518.9 μmol h−1 g−1. Such values are among the highest of state‐of‐the‐art COF photocatalysts.

The construction of layered covalent carbon nitride polymers based on tri-s-triazine units has been achieved by using nucleobases (adenine, guanine, cytosine, thymine and uracil) and urea to establish a two-dimensional semiconducting structure that allows band-gap engineering applications. This biomolecule-derived binary carbon nitride polymer enables the generation of energized charge carrier with light-irradiation to induce photoredox reactions for stable hydrogen production and heterogeneous organosynthesis of C-O, C-C, C-N and N-N bonds, which may enrich discussion on chemical reactions in prebiotic conditions by taking account of the photoredox function of conjugated carbonitride semiconductors that have long been considered to be stable HCN-derived organic macromolecules in space.

The reduction of CO2 with visible light is a highly sustainable method for producing valuable chemicals. The function‐led design of organic conjugated semiconductors with more chemical variety than that of inorganic semiconductors has emerged as a method for achieving carbon photofixation chemistry. Here, we report the molecular engineering of triazine‐based conjugated microporous polymers to capture, activate and reduce CO2 to CO with visible light. The optical band gap of the CMPs is engineered by varying the organic electron‐withdrawing (benzothiadiazole) and electron‐donating units (thiophene) on the skeleton of the triazine rings while creating organic donor–acceptor junctions to promote the charge separation. This engineering also provides control of the texture, surface functionality and redox potentials of CMPs for achieving the light‐induced conversion of CO2 to CO ambient conditions.