A facilitated-transport membrane embeds a carrier — often a transition metal salt or an amine-based complexing agent — inside a polymer matrix so that a target gas or ion is shuttled across the membrane faster than plain diffusion would allow. A standard selective membrane relies only on differences in solubility and diffusivity between the polymer and the gases being separated. The carrier gives facilitated-transport designs much higher selectivity for specific molecules, such as alkenes or carbon dioxide, which is why most of the patent activity in this dataset frames its claims around the carrier-polymer interaction rather than the base polymer alone.

The ranked leader in this dataset holds 101 records out of 749 in scope, well ahead of the fifth-ranked assignee at 37 and the tenth-ranked assignee at 22. The top five assignees combined account for 39.4% of all records, meaning a large share of the field's claim space sits with a small group of filers. Beyond the top ten, which together hold 56.1% of records, the ranking extends into a long tail of smaller filers, so a full landscape view needs both the leaders and that tail.

Filing peaked at 83 records in 2019, dipped afterward, and then grew again: from 2021 to 2024, the last years this data cut-off can treat as complete, filings rose 29%, from 17 to 22. Because publication typically lags filing by around 18 months, the 2025 and 2026 figures in any trend chart are still filling in and should not be read as a decline. On the evidence available, the field is rebuilding filing activity rather than winding down.

Separation-process claims under B01D appear in 85.6% of the 749 records in scope, making that the densest area by far. Chemistry-adjacent classes are much thinner: C08F addition-polymer chemistry appears in only 3.9% of records and H01M battery or fuel-cell integration in 5.3%. Because a single record can carry multiple IPC classes, these lighter classes represent genuine white space relative to the separation-process core, particularly for filers building carrier-polymer formulations tied to a specific end use like battery gas management.

US20040200355A1, filed by the Korea Institute of Science and Technology in 2004, describes a facilitated transport membrane combining a porous supported membrane with a second layer of transition metal salt physically dispersed — not chemically bonded — within a polymer that has no functional group able to complex with the salt. That physical-dispersion mechanism, as opposed to chemical complexation, is a distinct technical approach that later filings in alkene separation frequently reference. Anyone developing a similar carrier-polymer membrane should check their dispersion mechanism against this filing's claims before assuming a chemical-bonding approach clears it.