Porphyrin-Based COF 2D Materials: Variable Modification of Sensing Performances by Post-Metallization.

2D nanomaterials with flexibly modifiable surfaces are highly sought after for various applications, especially in room-temperature chemiresistive gas sensing. Here, we have prepared a series of COF 2D nanomaterials (porphyrin-based COF nanosheets (NS)) that enabled highly sensitive and specific-sensing of NO at room temperature. Different from the traditional 2D sensing materials, H -TPCOF was designed with a largely reduced interlayer interaction and predesigned porphyrin rings as modifiable sites on its surfaces for post-metallization. After post-metallization, the metallized M-TPCOF (M=Co and Cu) showed remarkably improved sensing performances. Among them, Co-TPCOF exhibited highly specific sensing toward NO with one of the highest sensitivities of all reported 2D materials and COF materials, with an ultra-low limit-of-detection of 6.8 ppb and fast response/recovery. This work might shed light on designing and preparing a new type of surface-highly-modifiable 2D material for various chemistry applications.