Silica-based covalent organic framework composite for efficient separation and enrichment of palladium and its heterogeneous catalysis application

•Novel covalent organic framework and silica-based composite adsorbents (Tp-Azo-COF/SiO2) were prepared.•Excellent selectivity (SFPd/[M] greater than 2653), kinetics and cycling performance (cycle number greater than 5) towards Pd(II).•Complete separation of Pd(II) from simulated HLLW achieved by dynamic column experiments.•Highly efficient enrichment (C/Co about 30) of Pd(II) for sustainability by dynamic column experiments.•First reduction process for adsorption product and better performance than commercial catalysts for hydrogen production.