[1] [1] H. Xie, T. Wang, J. Liang, Q. Li, S. Sun, Cu-based nanocatalysts for electrochemical reduction of CO2. Nano Today 21, 41–54 (2018). 10.1016/j.nantod.2018.05.001

[2] [2] A. Vasileff, C. Xu, Y. Jiao, Y. Zheng, S.-Z. Qiao, Surface and interface engineering in copper-based bimetallic materials for selective CO2 electroreduction. Chem 4, 1809–1831 (2018). 10.1016/j.chempr.2018.05.001

[3] [3] M. Li, Y. Ma, J. Chen, W. Luo, M. Sacchi et al., Residual chlorine induced cationic active species on porous Cu electrocatalyst for highly stable electrochemical co2 reduction to C2+. Angew. Chem. Int. Ed. 60, 11487–11493 (2021). 10.1002/anie.202102606

[4] [4] Y. Quan, J. Zhu, G. Zheng, Electrocatalytic reactions for converting CO2 to value-added products. Small Sci. 1, 2100043 (2021). 10.1002/smsc.202100043

[5] [5] M. Li, J.-N. Zhang, Rational design of bimetallic catalysts for electrochemical CO2 reduction reaction: a review. Sci. China Chem. 66, 1288–1317 (2023). 10.1007/s11426-023-1565-5

[6] [6] Y. Cheng, S. Zhao, B. Johannessen, J.-P. Veder, M. Saunders et al., Atomically dispersed transition metals on carbon nanotubes with ultrahigh loading for selective electrochemical carbon dioxide reduction. Adv. Mater. 30, e1706287 (2018).

[7] [7] H.B. Yang, S.-F. Hung, S. Liu, K. Yuan, S. Miao et al., Atomically dispersed Ni(i) as the active site for electrochemical CO2 reduction. Nat. Energy 3, 140–147 (2018). 10.1038/s41560-017-0078-8

[8] [8] H. Guo, D.-H. Si, H.-J. Zhu, Q.-X. Li, Y.-B. Huang et al., Ni single-atom sites supported on carbon aerogel for highly efficient electroreduction of carbon dioxide with industrial current densities. eScience 2, 295–303 (2022).

[9] [9] J. Gu, C.-S. Hsu, L. Bai, H.M. Chen, X. Hu, Atomically dispersed Fe3+ sites catalyze efficient CO2 electroreduction to CO. Science 364, 1091–1094 (2019). 10.1126/science.aaw7515

[10] [10] C. Zhang, S. Yang, J. Wu, M. Liu, S. Yazdi et al., Electrochemical CO2 reduction with atomic iron-dispersed on nitrogen-doped graphene. Adv. Energy Mater. 8, 1703487 (2018). 10.1002/aenm.201703487

[11] [11] X. Wang, Z. Chen, X. Zhao, T. Yao, W. Chen et al., Regulation of coordination number over single co sites: triggering the efficient electroreduction of CO2. Angew. Chem. Int. Ed. 57, 1944–1948 (2018). 10.1002/anie.201712451

[12] [12] Y. Pan, R. Lin, Y. Chen, S. Liu, W. Zhu et al., Design of single-atom Co-N5 catalytic site: A robust electrocatalyst for CO2 reduction with nearly 100% CO selectivity and remarkable stability. J. Am. Chem. Soc. 140, 4218–4221 (2018). 10.1021/jacs.8b00814

[13] [13] F. Yang, P. Song, X. Liu, B. Mei, W. Xing et al., Highly efficient CO2 electroreduction on ZnN4-based single-atom catalyst. Angew. Chem. Int. Ed. 57, 12303–12307 (2018). 10.1002/anie.201805871

[14] [14] D. Xue, H. Xia, W. Yan, J. Zhang, S. Mu, Defect engineering on carbon-based catalysts for electrocatalytic CO2 reduction. Nano-Micro Lett. 13, 5 (2020). 10.1007/s40820-020-00538-7

[15] [15] M. Li, H. Wang, W. Luo, P.C. Sherrell, J. Chen et al., Heterogeneous single-atom catalysts for electrochemical co2 reduction reaction. Adv. Mater. 32, 2001848 (2020). 10.1002/adma.202001848

[16] [16] W. Zheng, J. Yang, H. Chen, Y. Hou, Q. Wang et al., Atomically defined undercoordinated active sites for highly efficient co2 electroreduction. Adv. Funct. Mater. 30, 1907658 (2019). 10.1002/adfm.201907658

[17] [17] Y. Wang, Z. Chen, P. Han, Y. Du, Z. Gu et al., Single-atomic cu with multiple oxygen vacancies on ceria for electrocatalytic CO2 reduction to CH4. ACS Catal. 8, 7113–7119 (2018). 10.1021/acscatal.8b01014

[18] [18] Z. Weng, Y. Wu, M. Wang, J. Jiang, K. Yang et al., Active sites of copper-complex catalytic materials for electrochemical carbon dioxide reduction. Nat. Commun. 9, 415 (2018). 10.1038/s41467-018-02819-7

[19] [19] H. Yang, Y. Wu, G. Li, Q. Lin, Q. Hu et al., Scalable production of efficient single-atom copper decorated carbon membranes for CO2 electroreduction to methanol. J. Am. Chem. Soc. 141, 12717–12723 (2019). 10.1021/jacs.9b04907

[20] [20] Q. Zhao, C. Zhang, R. Hu, Z. Du, J. Gu et al., Selective etching quaternary max phase toward single atom copper immobilized mxene (Ti3C2Clx) for efficient CO2 electroreduction to methanol. ACS Nano 15, 4927–4936 (2021). 10.1021/acsnano.0c09755

[21] [21] H. Xu, D. Rebollar, H. He, L. Chong, Y. Liu et al., Highly selective electrocatalytic CO2 reduction to ethanol by metallic clusters dynamically formed from atomically dispersed copper. Nat. Energy 5, 623–632 (2020). 10.1038/s41560-020-0666-x

[22] [22] D. Karapinar, N.T. Huan, N. Ranjbar Sahraie, J. Li, D. Wakerley et al., Electroreduction of CO2 on single-site copper-nitrogen-doped carbon material: Selective formation of ethanol and reversible restructuration of the metal sites. Angew. Chem. Int. Ed. 58, 15098–15103 (2019).

[23] [23] K. Zhao, X. Nie, H. Wang, S. Chen, X. Quan et al., Selective electroreduction of CO2 to acetone by single copper atoms anchored on N-doped porous carbon. Nat. Commun. 11, 2455 (2020). 10.1038/s41467-020-16381-8

[24] [24] Y. Cai, J. Fu, Y. Zhou, Y.-C. Chang, Q. Min et al., Insights on forming N, O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane. Nat. Commun. 12, 586 (2021). 10.1038/s41467-020-20769-x

[25] [25] A. Guan, Z. Chen, Y. Quan, C. Peng, Z. Wang et al., Boosting CO2 electroreduction to CH4 via tuning neighboring single-copper sites. ACS Energy Lett. 5, 1044–1053 (2020). 10.1021/acsenergylett.0c00018

[26] [26] X. Li, H. Rong, J. Zhang, D. Wang, Y. Li, Modulating the local coordination environment of single-atom catalysts for enhanced catalytic performance. Nano Res. 13, 1842–1855 (2020). 10.1007/s12274-020-2755-3

[27] [27] Y. Zheng, Y. Jiao, Y. Zhu, Q. Cai, A. Vasileff et al., Molecule-level g-C3N4 coordinated transition metals as a new class of electrocatalysts for oxygen electrode reactions. J. Am. Chem. Soc. 139, 3336–3339 (2017). 10.1021/jacs.6b13100

[28] [28] X. Wang, X. Chen, A. Thomas, X. Fu, M. Antonietti, Metal-containing carbon nitride compounds: a new functional organic–metal hybrid material. Adv. Mater. 21, 1609–1612 (2009). 10.1002/adma.200802627

[29] [29] J. Gu, M. Jian, L. Huang, Z. Sun, A. Li et al., Synergizing metal–support interactions and spatial confinement boosts dynamics of atomic nickel for hydrogenations. Nat. Nanotechnol. 16, 1141–1149 (2021). 10.1038/s41565-021-00951-y

[30] [30] S. Cao, H. Li, T. Tong, H.-C. Chen, A. Yu et al., Single-atom engineering of directional charge transfer channels and active sites for photocatalytic hydrogen evolution. Adv. Funct. Mater. 28, 1802169 (2018). 10.1002/adfm.201802169

[31] [31] H. Zhang, C. Wang, H. Luo, J. Chen, M. Kuang et al., Iron nanoparticles protected by chainmail-structured graphene for durable electrocatalytic nitrate reduction to nitrogen. Angew. Chem. Int. Ed. 62, e202217071 (2023).

[32] [32] X. Zou, X. Huang, A. Goswami, R. Silva, B.R. Sathe et al., Cobalt-embedded nitrogen-rich carbon nanotubes efficiently catalyze hydrogen evolution reaction at all ph values. Angew. Chem. Int. Ed. 53, 4372–4376 (2014). 10.1002/anie.201311111

[33] [33] F. He, K. Li, C. Yin, Y. Wang, H. Tang et al., Single Pd atoms supported by graphitic carbon nitride, a potential oxygen reduction reaction catalyst from theoretical perspective. Carbon 114, 619–627 (2017). 10.1016/j.carbon.2016.12.061

[34] [34] X. Chen, X. Zhao, Z. Kong, W.-J. Ong, N. Li, Unravelling the electrochemical mechanisms for nitrogen fixation on single transition metal atoms embedded in defective graphitic carbon nitride. J. Mater. Chem. A 6, 21941–21948 (2018). 10.1039/C8TA06497K

[35] [35] Q. Wang, K. Liu, J. Fu, C. Cai, H. Li et al., Atomically dispersed s-block magnesium sites for electroreduction of CO2 to CO. Angew. Chem. Int. Ed. 60, 25241–25245 (2021). 10.1002/anie.202109329

[36] [36] Y. Jiao, Y. Zheng, P. Chen, M. Jaroniec, S.-Z. Qiao, Molecular scaffolding strategy with synergistic active centers to facilitate electrocatalytic co2 reduction to hydrocarbon/alcohol. J. Am. Chem. Soc. 139, 18093–18100 (2017). 10.1021/jacs.7b10817

[37] [37] G. Kresse, J. Furthmuller, Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996). 10.1103/PhysRevB.54.11169

[38] [38] J.P. Perdew, K. Burke, M. Ernzerhof, Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996). 10.1103/PhysRevLett.77.3865

[39] [39] B. Hammer, L.B. Hansen, J.K. Norskov, Improved adsorption energetics within density-functional theory using revised perdew-burke-ernzerhof functionals. Phys. Rev. B 59, 7413 (1999). 10.1103/PhysRevB.59.7413

[40] [40] S. Grimme, Semiempirical GGA-type density functional constructed with a long-range dispersion correction. J. Comput. Chem. 27, 1787–1799 (2006). 10.1002/jcc.20495

[41] [41] E. Skúlason, V. Tripkovic, M.E. Björketun, S. Gudmundsdóttir, G. Karlberg et al., Modeling the electrochemical hydrogen oxidation and evolution reactions on the basis of density functional theory calculations. J. Phys. Chem. C 114, 18182–18197 (2010). 10.1021/jp1048887

[42] [42] G. Gao, A.P. O’Mullane, A. Du, 2D Mxenes: a new family of promising catalysts for the hydrogen evolution reaction. ACS Catal. 7, 494–500 (2017). 10.1021/acscatal.6b02754

[43] [43] Z. Jin, P. Li, Y. Meng, Z. Fang, D. Xiao et al., Understanding the inter-site distance effect in single-atom catalysts for oxygen electroreduction. Nat. Catal. 4(7), 615–622 (2021). 10.1038/s41929-021-00650-w

[44] [44] T. Zhang, W. Li, K. Huang, H. Guo, Z. Li et al., Regulation of functional groups on graphene quantum dots directs selective CO2 to CH4 conversion. Nat. Commun. 12, 5265 (2021). 10.1038/s41467-021-25640-1

[45] [45] R.M. Yadav, Z. Li, T. Zhang, O. Sahin, S. Roy et al., Amine-functionalized carbon nanodot electrocatalysts converting carbon dioxide to methane. Adv. Mater. 34, 2105690 (2022). 10.1002/adma.202105690

[46] [46] Y. Xiao, G. Tian, W. Li, Y. Xie, B. Jiang et al., Molecule self-assembly synthesis of porous few-layer carbon nitride for highly efficient photoredox catalysis. J. Am. Chem. Soc. 141, 2508–2515 (2019). 10.1021/jacs.8b12428

[47] [47] X. Zou, R. Silva, A. Goswami, T. Asefa, Cu-doped carbon nitride: Bio-inspired synthesis of H2-evolving electrocatalysts using graphitic carbon nitride (g-C3N4) as a host material. Appl. Surf. Sci. 357, 221–228 (2015). 10.1016/j.apsusc.2015.08.197

[48] [48] J. Ran, T.Y. Ma, G. Gao, X.-W. Du, S.Z. Qiao, Porous P-doped graphitic carbon nitride nanosheets for synergistically enhanced visible-light photocatalytic h2 production. Energ. Environ. Sci. 8, 3708–3717 (2015). 10.1039/C5EE02650D

[49] [49] Q. Han, B. Wang, J. Gao, Z. Cheng, Y. Zhao et al., Atomically thin mesoporous nanomesh of graphitic C3N4 for high-efficiency photocatalytic hydrogen evolution. ACS Nano 10, 2745–2751 (2016). 10.1021/acsnano.5b07831

[50] [50] B. Yue, Q. Li, H. Iwai, T. Kako, J. Ye, Hydrogen production using zinc-doped carbon nitride catalyst irradiated with visible light. Sci. Technol. Adv. Mater. 12, 034401 (2011).

[51] [51] Y. Zhou, F. Che, M. Liu, C. Zou, Z. Liang et al., Dopant-induced electron localization drives CO2 reduction to C2 hydrocarbons. Nat. Chem. 10, 974–980 (2018). 10.1038/s41557-018-0092-x

[52] [52] H. Shang, X. Zhou, J. Dong, A. Li, X. Zhao et al., Engineering unsymmetrically coordinated Cu-S1N3 single atom sites with enhanced oxygen reduction activity. Nat. Commun. 11, 3049 (2020). 10.1038/s41467-020-16848-8

[53] [53] X. Zhao, Y. Cao, L. Duan, R. Yang, Z. Jiang et al., Unleash electron transfer in C–H functionalization by mesoporous carbon-supported palladium interstitial catalysts. Natl. Sci. Rev. 8, nwaa126 (2020).

[54] [54] M. Li, N. Song, W. Luo, J. Chen, W. Jiang et al., Engineering surface oxophilicity of copper for electrochemical CO2 reduction to ethanol. Adv. Sci. 10, 2204579 (2022). 10.1002/advs.202204579

[55] [55] J. Xu, X. Zheng, Z. Feng, Z. Lu, Z. Zhang et al., Organic wastewater treatment by a single-atom catalyst and electrolytically produced H2O2. Nat. Sustain. 4, 233–241 (2021). 10.1038/s41893-020-00635-w

[56] [56] J. Liang, Y. Zheng, J. Chen, J. Liu, D. Hulicova-Jurcakova et al., Facile oxygen reduction on a three-dimensionally ordered macroporous graphitic C3N4/carbon composite electrocatalyst. Angew. Chem. Int. Ed. 51, 3892–3896 (2012). 10.1002/anie.201107981

[57] [57] G. Zhu, R. Guo, W. Luo, H.K. Liu, W. Jiang et al., Boron doping-induced interconnected assembly approach for mesoporous silicon oxycarbide architecture. Natl. Sci. Rev. 8, nwaa152 (2020).

[58] [58] Y. Zhang, L.-Z. Dong, S. Li, X. Huang, J.-N. Chang et al., Coordination environment dependent selectivity of single-site-Cu enriched crystalline porous catalysts in CO2 reduction to CH4. Nat. Commun. 12, 6390 (2021). 10.1038/s41467-021-26724-8

[59] [59] J. Feng, L. Zheng, C. Jiang, Z. Chen, L. Liu et al., Constructing single Cu-N3 sites for CO2 electrochemical reduction over a wide potential range. Green Chem. 23, 5461–5466 (2021). 10.1039/D1GC01914G

[60] [60] J.-D. Yi, R. Xie, Z.-L. Xie, G.-L. Chai, T.-F. Liu et al., Highly selective CO2 electroreduction to CH4 by in situ generated Cu2O single-type sites on a conductive mof: stabilizing key intermediates with hydrogen bonding. Angew. Chem. Int. Ed. 59, 23641–23648 (2020). 10.1002/anie.202010601

[61] [61] Y. Pan, H. Li, J. Xiong, Y. Yu, H. Du et al., Protecting the state of cu clusters and nanoconfinement engineering over hollow mesoporous carbon spheres for electrocatalytical C-C coupling. Appl. Catal. B: Environ. 306, 121111 (2022).

[62] [62] Y.-Y. Liu, H.-L. Zhu, Z.-H. Zhao, N.-Y. Huang, P.-Q. Liao et al., Insight into the effect of the d-orbital energy of copper ions in metal–organic frameworks on the selectivity of electroreduction of CO2 to CH4. ACS Catal. 12(5), 2749–2755 (2022). 10.1021/acscatal.1c04805

[63] [63] Y. Cao, S. Chen, Q. Luo, H. Yan, Y. Lin et al., Atomic-level insight into optimizing the hydrogen evolution pathway over a Co1-N4 single-site photocatalyst. Angew. Chem. Int. Ed. 129(40), 12359–12364 (2017). 10.1002/ange.201706467