Lithium metal batteries (LMBs) have undergone extensive development owing to their remarkable energy storage capabilities. Nevertheless, safety concerns, including thermal runaway and lithium dendrites, impede their application. Modification of separators can effectively overcome the limitations of commercial separators, such as inferior thermal stability and poor wettability, and consequently alleviate the damage induced by lithium dendrites. Here, we synthesize a three-dimensional P-type molecular sieve and develop a lamellar-structured material, which is then used to fabricate composite separators by coating it onto polypropylene (PP) separators (denoted as PP@3DP and PP@TOC/3DP). Experimental results demonstrate that, in comparison with pristine PP separators, the composite separators display significantly enhanced physical properties, such as improved porosity, thermal stability, and tensile strength. The battery assembled with the PP@TOC/3DP separator exhibits a higher initial discharge specific capacity (167.96 mAh·g⁻¹), superior rate performance, and enhanced cycling stability at 0.5 C, compared to batteries assembled with the PP separator and the PP@3DP separator. Moreover, after 1000 cycles at 2.0 C, it sustains a capacity retention rate of 95.90% with a specific capacity of 140.36 mAh·g⁻¹. These findings strongly attest to the excellent performance of PP@TOC/3DP and pave the way for molecular sieve functionalized separators in LMBs.