Water-Soluble Metal Phthalocyanines Enable Molecularly Dispersed Heterogeneous Electrochemical CO₂ Conversion

Molecular electrocatalysts offer the prospect of atomically defined active sites and tunable reactivity, yet their integration into heterogeneous systems is frequently hindered by limited site accessibility and reduced catalytic performance. Overcoming molecular aggregation and improving electronic coupling with conductive supports are essential for translating molecular precision into practical electrocatalytic devices. Here we show that water-soluble, tetrasulfonate-substituted metallophthalocyanines (MPcTs) spontaneously assemble onto carbon black (CB) through π-π interactions, forming highly dispersed and electronically coupled catalytic sites. The resulting MPcTs/CB catalyst enables highly selective CO₂-to-CO conversion in aqueous media, affording near-quantitative Faradaic efficiencies and sustained performance over 60 h of continuous operation. Systematic investigations confirm a heterogeneous electrocatalytic pathway, while optimized flow-cell configurations deliver current densities up to 500 mA cm^{- 2} with high CO selectivity. This study demonstrates a simple, generalizable strategy to bridge molecular precision and heterogeneous practicality, advancing the design of scalable, high-performance molecular electrocatalysts for CO₂ electroreduction in aqueous media.