Filing activity is concentrated among a small group of universities, national labs and oil-and-gas majors, with the top 5 assignees holding 28.3% of the 2,363 records in scope and the top 10 holding 39.6%. This concentration means core sorbent-composition and swing-adsorption process claims are largely occupied by a handful of holders, though a long tail of single- and few-filing entrants remains active around the edges. Recent-year momentum data shows some of the largest holders have slowed or stopped filing, which is worth checking before assuming a claim is still being actively defended.

Both routes appear heavily in the search scope, but they map to different IPC classes: MOF composite claims tend to sit in C07F (organo-metallic compounds) and B01J (catalysis/chemical processes), while amine-functionalized sorbent claims lean on B01D (separation) and C01B (inorganic compounds). MOF filings more often target gas storage, refrigeration and specialty separation applications, whereas amine-functionalized sorbent claims concentrate on cyclic CO2 capture and regeneration process parameters like working capacity and steam stripping. Reviewing the specific IPC combination on a target patent is a faster way to tell the two routes apart than reading the abstract alone.

Filings peaked at 265 in 2021 and dropped to 162 by 2024, a -39% change the dataset supports directly. Part of this is a genuine slowdown in new filing activity from several major holders, visible in the recent-year momentum figures. But part of it is a data artefact: patent publication lags filing by roughly 18 months, so the counts for 2025 and 2026 are still incomplete and will rise as more applications publish, meaning the true 2025-2026 filing rate cannot yet be judged from this trend line.