This Study Investigated the Potential of Polymer of Intrinsic Microporosity (PIM-1) and Ce(OH)4@PIM-1 Composites for Adsorption of the Nerve Agent Simulant, Dimethyl Methylphosphonate (DMMP). through Experimental Investigations It Was Demonstrated that These Composite Adsorbents Exhibit Excellent Gas-Phase DMMP Adsorption Performance, with High Uptake Capacities and Relatively Fast Kinetics. This Study Further Examined the Effect of Two Composite's Preparation Methods, Namely Matrix Incorporation and Surface Coating, on the DMMP Adsorption Performance of Ce(OH)4@PIM-1. the Results Revealed that Coating of Ce(OH)4 on the PIM-1 Surface Gives Rise to Faster Adsorption Kinetics Than its Incorporation into the Polymer Matrix at Fixed 30 Wt % Loading, with Ce30@PIM-C and Ce30@PIM-I Composites Achieving 76 and 41% of their Saturation Capacities after 3 H of Exposure, Respectively. after 1 H of Exposure to DMMP Vapor, the Maximum Adsorption Rate Observed Was 581 Mg/g·h over Ce30@PIM-C at 200 °C, Whereas after 34 H, the Ce30@PIM-I Composite Adsorbent Exhibited a Maximum Uptake of 1558 Mg/g. the Adsorption of DMMP over These Composites Was Found to Be Essentially Chemisorption, as Opposed to the Bare PIM-1. the Findings Highlight the Potential of PIM-1-Based Composites in Capturing Chemical Warfare Agents and their Simulants, with Implications as Protective Clothing or Filters in Hazardous Environments.