Proton‐Coupling Electron Transfer Kinetics Modulation via Substitution Isomerism of Amino Groups in MOFs to Switch CO ₂ Photoreduction Pathways from HCOOH to CH ₃ COOH

Abstract

Abstract Selective photoreduction of CO 2 into high‐value C2 products is highly desirable but challenging due to the high‐energy‐barrier C‐C coupling and sluggish proton‐coupling electron transfers (PCET). Herein, CsPbBr 3 (CPB) quantum dots are in‐situ encapsulated within amino‐functionalized Fe/UiO‐67‐X (X = meta ‐NH 2 , ortho ‐NH 2 , ortho ‐2NH 2 ) frameworks for efficient CO 2 photoreduction. X‐ray absorption spectroscopy confirms the presence of charge‐asymmetrical ZrFe sites that promote C‐C coupling and the covalently‐connected Pb‐N electron‐transfer “bridge” that enhances carrier kinetics. Notably, the o ‐2NH 2 ‐functionalized CPB@Fe/UiO‐67‐ o ‐2NH 2 achieves a CH 3 COOH productivity of 257.22 µmol·g −1 ·h −1 with 98.72% selectivity, whereas the m ‐NH 2 ‐substituted analog (CPB@Fe/UiO‐67‐ m ‐NH 2 ) exclusively produces HCOOH. Comprehensive analyses demonstrate that the o ‐NH 2 groups facilitate ultrafast electron transfer via a near Pb–N bridge and organize interfacial H 2 O into proton‐conducting networks to ensure synchronized proton‐supply. In‐situ DRIFT and DFT calculations confirm that the o ‐NH 2 ‐induced rapid PCETdrives the conversion of * COOH at Zr sites to * CO, which subsequently couples with stabilized * COOH at Fe sites to form the critical * OC‐COOH with the lowest energy barrier compared to * HOOC‐COOH or * OC‐CO pathways. This work establishes a design paradigm that necessitates the “temporal alignment” and “spatial coupling” of H⁺ and e − at active sites for achieving high‐performance CO 2 ‐to‐C2 photoreduction by modulating interfacial electron‐proton dynamics through simple group isomerism.