Regulating Water Adsorption Sites of Keto-Enamine COF by Base Exfoliation and Deprotonation for Enhanced Humidity Response.

Covalent organic framework (COF) has received much attention owing to its unique framework structure formed by diverse organic units. However, challenges, including low conductivity, structure instability, and limited control of adsorption and desorption processes, stimulate the modification of COF in electronic sensors. Herein, inspired by the alterable structure of COF in different solvents, a facile base exfoliation and deprotonation method is proposed to regulate the water adsorption sites and improve the intrinsic conductivity of TpPa-1 COF. TpPa-1 COF powders are exfoliated to nanosheets to increase water adsorption, while the deprotonation is utilized to adjust the affinity of water molecules on TpPa-1 COF framework, contributing to water accumulation in the 1D pores. The as-fabricated TpPa-1 COF sensor exhibits a decreased recovery time from 419 to 49 s, forming a linear relation between relative humidity (RH) value and humidity response. The excellent chemical stability of the covalent bond of TpPa-1 COF contributes to the excellent stable device performance in 30 days, promoting further integration and data analysis in respiration monitoring.