Abstract An efficient material is needed to develop selective and effective sensing/removal systems with high flexibility, and low capital cost for control the capturing of toxic ions. In this study, we designed ligand immobilized mesoporous adsorbent for ultra-trace Pb(II) monitoring and removal from wastewater. The adsorbent was synthesized by indirect immobilization of 4-tert-octyl-4-((phenyl)diazenyl)phenol onto inorganic mesoporous silica. This adsorbent exhibited the large surface area-to-volume ratios and uniformly shaped pores in case cavities, and its active sites kept open functionality to taking up Pb(II). The applicability of the adsorbent for Pb(II) detection and removal was assessed, and the efficient parameters such as solution pH, contacting time, initial Pb(II) concentration and ionic strength of competing ions were measured. The effective pH range for detection and removal systems was at the neutral region. The data revealed that the adsorbent was able to detect the ultra-trace Pb(II) ions with high sensitivity and selectivity by charge transfer (intense π–π transition) transduction mechanism. Then the adsorbent proved to have an efficient ability for continuous Pb(II) monitoring and removal even on-site and in situ chemical analyses. The maximum sorption capacity and limit of detection were 200.80mg/g and 0.12μg/L, respectively. The adsorbent was reused in several cycles without significant deterioration after elution with a suitable eluent (0.10M HCl). Therefore, the design of mesoporous adsorbent has a great potentiality to be used in selective Pb(II) detection/removal from wastewater. Large-scale studies are recommended to confirm these promising results from the laboratory scale.