As a green energy carrier, a potential fuel and an essential chemical for the manufacturing of fertilizers, plastics, and explosives, ammonia (NH3) is currently produced by Haber−Bosch process. However, the process converting nitrogen (N2) into NH3 under strict conditions consumes substantial energy and releases enormous greenhouse gases. In the context of the global energy crisis and increasing greenhouse effect, it is urgent to explore mild, green, sustainable, and economic nitrogen‐fixation strategies. Very recently, photocatalytic nitrogen‐fixation reactions, including nitrogen reduction reaction (NRR) and nitrogen oxidation reaction (NOR), have aroused widespread attention due to its environmental friendliness and cost‐effectiveness. To achieve high photocatalytic performance and selectivity, it is necessary to design photocatalyst and its photoreaction system reasonably to optimize the light absorption, charge separation, mass transport, adsorption, and activation of N2 as well as proton/electron transfer. This review gives an overview of fundamentals, performance evaluation, and recent progress of the photocatalytic nitrogen‐fixation reactions. The photocatalysts and their design strategies are classified, and several suggestions are given for the analysis of the existing photocatalytic nitrogen‐fixation systems. Finally, a short perspective on the existing challenges and future opportunities are outlined for providing insights into the development of high‐efficiency photocatalytic systems for artificial N2 fixation.

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unsatisfactory conversion efficiency and product selectivity, and thus seeking novel electrocatalysts for highly active and selective CO 2 RR is a key issue. [7,8] Recently, carbon-based materials and complexes containing M-N 4 single-atom sites have been widely used as CO 2 RR electrocatalysts owing to their easy-tocontrol and highly exposed single-atom active sites. [9][10][11][12] Among them, metal phthalocyanines (MPcs) with unique M-N 4 units have been extensively used as efficient electrocatalyst since the metal center (M = Mn, Fe, Co, Ni, or Cu) has significant impact on the CO 2 RR performance. [13][14][15] For instance, it was reported that CoPc has a higher Faraday efficiency (99%) than the other MPcs at −0.80 V due to the moderate *CO binding energy at the Co active site, which is beneficial to the *COOH formation and the *CO desorption. [13] However, the poor intrinsic conductivity of such molecular catalysts usually results in low current density. [14,15] Although integrating these molecular catalysts with carbon substrate (e.g., carbon black, carbon nanotubes, or graphene) to form hybrid material can improve the conductivity, it is difficult to solve the uniformity of catalytic sites due to the molecular agglomeration, which usually cause an unsatisfactory CO 2 RR activity and stability. [16][17][18][19][20] Assembling the M-N 4 single-site molecules into covalent organic frameworks (COFs) or covalent organic polymers (COPs) is expected to be an ideal way since the catalytically active sites in such materials are usually separated by the linking units so as to expose more active sites, and the porous structure also allows rapid mass transport. [21][22][23][24][25][26][27][28][29] In addition to facilitating the mechanism research due to the well-defined metal center, those COFs/COPs also have some attractive features, such as controllable structure and pore size, good chemical stability, and easy composite with other materials. [30][31][32] Especially, the controllable pore size shows great application prospects in electrochemical and gas separation applications. [27,33] For example, when the phthalocyanine in CuPcF 8 -CoPc COF is replaced by naphthalocyanine, the pore size is enlarged from 1.1 to 1.3 nm, and thus the CO 2 RR activity was improved obviously. [27] Besides regulating the pore size, introducing electron-rich building blocks into COFs or COPs is also beneficial for the catalytic process. For example, porphyrin with electron-rich conjugated structure can transfer electrons to the catalytic Covalent organic frameworks (COFs) have been applied as potential electrocatalysts for CO 2 reduction reaction (CO 2 RR) due to their adjustable architecture and porous feature. Herein, tetraanhydrides of 2,3,9,10,16,17,23,24-octacarboxyphthalocyanine cobalt(II) (CoTAPc) are used as nodes to couple with 5,15-di(4-aminophenyl)-10,20-diphenylporphyrin (DAPor) or 5,15,10,20-tetrayl(4-aminophenyl)porphyrin (TAPor) via imidization reaction to fabricate novel coupled phthalocyanine-porphyrin Type 1:2 (CoPc-2...

A novel heterometallic Zn‐/Co‐porphyrin conjugated polymer (ZnCoP‐F CP) with its Co‐porphyrin bridging unit bearing two perfluorophenyls is synthesized via a Sonogashira coupling reaction. The resulting ZnCoP‐F CP without the Pt cocatalyst exhibits broadband (UV–vis–NIR) light‐driven hydrogen evolution activity of 83 µmol h−1, which is more than twice that (39 µmol h−1) of its counterpart (ZnCoP CP) with the Co‐porphyrin unit bearing two phenyls. Furthermore, an apparent quantum yield of 6.92%, 5.50%, 5.78%, 3.17%, and 0.73% is achieved from the ZnCoP‐F CP illuminated at 400, 500, 550, 700, and 850 nm monochromatic light, respectively. The enhanced performance of ZnCoP‐F CP can be attributed to the high electron‐withdrawing capacity of its perfluorophenyls and the highly dispersed Co centers in Co‐porphyrin bridging units serving as single‐atom catalytic sites (CoN4), which facilitate the formation of periodic type II‐like heterojunctions and the fast charge transfer from Zn‐porphyrin to Co‐porphyrin units for hydrogen evolution reaction. The broadband‐responsive feature is due to the large π‐conjugated system through the whole 2D internal framework of the porphyrin polymer. This work opens a new path to fabricate porphyrin‐based polymer with an efficient and broadband‐responsive hydrogen evolution system.