Modulating NH_(2)Lewis Basicity in CTF-NH_(2)through Donor-Acceptor Groups for Optimizing Photocatalytic Water Splitting

Photocatalytic water splitting(PWS)provides an optimal approach for the sustainable production of green hydrogen.NH_(2)-modified covalent triazine frameworks(CTFs-NH_(2))hold potential in PWS due to robust light uptake,optimal charge separation,and considerable redox potential.However,the high surface reaction barriers hinder the efficiency of PWS owing to the conversion difficulty of intermediate products.Modulating the Lewis basicity of NH_(2)on CTFs offers a feasible route for addressing this challenge.In this work,electron-donating ethyl(C_(2)F_(5))and electronwithdrawing 5-fluoroethyl groups(C_(2)F_(5))are introduced at the para position of amine groups,producing C_(2)F_(5)-CTF-NH_(2)and C_(2)F_(5)-CTF-NH_(2),to adjust the Lewis basicity of CTF-NH_(2).Through DFT calculations,the optical properties,excited states,electronic structures,dipole moments,and surface reaction processes of the CTF-NH_(2),C_(2)F_(5)-CTF-NH_(2)and C_(2)F_(5)-CTF-NH_(2)are simulated.The results indicate that the electron-withdrawing C_(2)F_(5)group can decrease the electron density and Lewis basicity on NH_(2),thereby lowering the energy barriers for hydrogen and oxygen evolution reactions,effectively ameliorating the PWS efficiency of CTF-NH_(2).This work unveils an innovative approach for donor-acceptor-regulated CTFs for the application of PWS.