{
  "abstract": "Machine learning screens metal–organic frameworks (MOFs) for CO2 capture, and 2026 studies on enumerated databases have converged on topology hold-out as a test of topological transferability, presupposing untested separability of topology and chemistry. They are not: on hMOF (324,426 structures), 74.7% of coarse compositions (61.3% of structures) occur in a single topology, and for seven of hMOF's eleven topologies removing one topology leaves every structure with no chemical counterpart in training; the confound replicates on ARC-MOF (99.3% coarse single-topology), which is not independent of hMOF, so only a leave-one-source-out bound (98.6–99.8%) is claimed. On the isoreticular pcu ↔ nbo pair, removing the matched topology degrades nbo-side MAE by 70.0% while a sizematched control leaves it unchanged, and across the shared 25,000-sample support set the top-1% hit rate falls from 50.4% to 19.3% (five seeds). Yet the topology penalty is not explained by chemistry alone: holding out the composite chemistry key instead retains R2 = 0.674 against topology's 0.379, so the composition counts fix the identity of the withheld chemistry, not its cost. Topology hold-out should therefore not be read as a clean test of topological transferability, and grouped-split reports should first disclose the confound structure and chemical granularity, for which we provide a reporting checklist.",
  "abstract_shown": true,
  "affiliations": [
    "College of Chemical Engineering",
    "Nanjing Tech University"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 1,
  "authors": [
    {
      "affs": [
        0,
        1
      ],
      "name": "Tao Wang"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/479agxnpphr5g.bib",
  "cited_by": 0,
  "doi": "10.26434/chemrxiv.15010692/v1",
  "fulltext_url": null,
  "id": "479agxnpphr5g",
  "issns": [],
  "landing_url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010692/v1",
  "language": null,
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "1604|Metal-Organic Frameworks: Synthesis and Applications"
    ]
  ],
  "openalex": "W7223057179",
  "pdf_url": "https://chemrxiv.org/doi/pdf/10.26434/chemrxiv.15010692/v1",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-20",
  "publisher": "American Chemical Society (ACS)",
  "ris": "https://research.draconitic.com/paper/479agxnpphr5g.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:24Z",
      "native_id": "10.26434/chemrxiv.15010692",
      "source": "chemrxiv",
      "url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010692/v1"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "openalex:1604|Metal-Organic Frameworks: Synthesis and Applications",
      "subfield": "inorganic"
    }
  ],
  "title": "A grouped split silently removes the chemistry entangled with its grouping variable: the case of MOF topology hold-out",
  "title_text": "A grouped split silently removes the chemistry entangled with its grouping variable: the case of MOF topology hold-out",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:24Z",
  "url": "https://research.draconitic.com/paper/479agxnpphr5g",
  "venue": "ChemRxiv",
  "versions": []
}