Synergy of cyano groups and cobalt single atoms in graphitic carbon nitride for enhanced bio-denitrification

Bio-denitrification plays a crucial role in the purification of nitrogen contaminated water, yet the low efficiency of the pure biological system often leads to the accumulation of harmful intermediates. Semi-biological catalysis provides an effective approach to improving the reaction efficiency through hybridizing artificial nanomaterials with natural organisms, yet the application of this strategy in bio-denitrification is limited. In this study, the effect of surface engineered carbon nitride on the denitrification capability of denitrifying bacteria was investigated. We found that cyano groups availed the biotic-abiotic interactions, while immobilized cobalt single atoms attenuated the local electrostatic repulsion. This synergistic effect endowed carbon nitride modified with cobalt atoms and cyano groups (Co/C3N4-C) with the unexpected acceleration of bio-denitrification reaction, without the accumulation of harmful intermediates. According to the metabolomics analysis, this improvement was attributed to the moderate metabolic adaptation caused by nanoelicitor, which induced dramatically boosted electron transfer and energy supply for extracellular polymeric substance (EPS) secretion. The elevation of intracellular iron level increased the activities of denitrification reductase, which was evidenced by metatranscriptomic analysis. Our results not only demonstrate the great potential of carbon nitride as an artificial elicitor for biological regulation, but also shed light on comprehending the complicated biotic-abiotic interactions for versatile application.