Positional Effects of Single‐Atom Active Sites in 1D Porphyrinic COFs on Photocatalytic CO ₂ Reduction

Abstract

ABSTRACT The selective photocatalytic reduction of carbon dioxide (CO 2 ) to methane (CH 4 ) remains a formidable challenge due to the demanding eight‐electron/proton‐coupled reduction process. Here, we report a positional engineering strategy for tailoring the spatial distribution of single‐atom active sites within 1D porphyrinic covalent organic frameworks (CPOF‐13‐M 1 ‐M 2 , where M 1 = H/Cu and M 2 = H/Cu), enabling tunable catalytic selectivity. By selectively positioning Cu atoms at either edge‐ or central‐positioned porphyrin sites of the framework, or both, we elucidate how active‐site location governs charge‐carrier dynamics and reaction pathways. Central Cu sites favor CO formation via *CO desorption, whereas edge‐positioned Cu sites promote sequential hydrogenation of *CO toward CH 4 through multielectron transfer, achieving a CH 4 production rate of 31.6 µmol g −1 h −1 with 92.9% electron selectivity. Dual‐site configurations exhibited intermediate selectivity, reflecting the competing catalytic preferences of the two differently positioned active sites. These findings establish active‐site positional engineering as a versatile design principle for tailoring photocatalytic pathways in COF‐based catalysts, opening new avenues for the rational design of reticular materials for solar fuel generation.