In Situ Growth of 3D Carnation Flower-Like β-Ni(OH)₂ on Conductive Coordination Polymer for Humidity Sensing

Conductive coordination polymers (CCPs) have emerged as promising chemoresistive sensor materials due to their highly tunable structures and the abundance of active sites that facilitate electronic signal changes. However, CCP-based sensor devices currently suffer from prolonged response times, requiring urgent solutions to improve their responsiveness and overall performance. Herein, a long-range ordered surface distribution of hydroxyl functional groups with a "seed effect" on the CCP Cu(SPh-OH)_n is utilized to enable in situ growth of 3D carnation flower-like β-Ni(OH)₂. The integration of the flower-like β-Ni(OH)₂ introduces an intricate 3D structure that not only increases the opportunities for water molecule interaction but also promotes the self-oxidation and reduction of Cu(SPh-OH)_n. This augmentation in carrier concentration markedly elevates the device's proficiency in humidity sensing. The humidity response of the Cu(SPh-OH)_n@β-Ni(OH)₂ composite at 97% relative humidity (RH) is nearly 15-fold greater than that of its individual components. The developed sensor features a wide detection range (11%-97% RH), fast response time (2.02 s), and a short recovery time (2.42 s), together with outstanding long-term stability (>50 days). Furthermore, it is compatible with flexible substrates, enabling non-contact humidity sensing and detection. This research provides valuable insights into advancing the use of CCPs for high-performance humidity sensing applications.