Enhanced Electrochemiluminescence of Porphyrin‐Based Hydrogen‐Bonded Organic Frameworks at Low Positive Potential via Substituent‐Induced Outer‐Sphere Microenvironment Modulation

Abstract The porphyrin‐based hydrogen‐bonded organic framework (HOF) offers a superior platform for decoding electrochemiluminescence (ECL) via controlling charge transfer due to its higher solubility, chemical stability, and tunable framework behavior. In this research, three kinds of HOFs including TDPP‐HOF, TCPP‐HOF, and TCNPP‐HOF are synthesized based on a porphyrin tectonic plate decorated with 2,4‐diaminotriazinyl (DAT), carboxyl, and nitrile moieties to study their ECL performances. The hydrazine as the coreactant can trigger TDPP‐HOF at the low‐excited positive potential to generate 15.8‐ and 112.9‐fold enhancement in ECL signal than TCNPP‐HOF and TCPP‐HOF. Experimental results and density functional theory calculations verify that TDPP‐HOF with a lower bandgap and a larger binding energy (ΔE) between coreactant and HOF is beneficial to intrareticular charge transfer (ICT), facilitating the enhancement of ECL performance. These results indicate that the peripheral substituents can establish a specialized outer‐sphere microenvironment around the porphyrin center to tune both the HOF activity and the ECL performance. As a proof of concept, a simple TDPP‐HOF‐based ECL sensor is constructed to sensitively detect phenolic compounds. This research provides a new avenue for improving the ECL performance via modulating the outer‐sphere microenvironment of HOFs.