{
  "abstract": "The framework material, calcium poly(heptazine imide) or CaPHI, is reportedly capable for CO 2 absorption, although harsh conditions from literature synthesis method result in low and unpredictable yield that hinders evaluation of its applicability for CO 2 capture and conversion (CCC). This work presents a synthesis procedure for CaPHI with cross-laboratory reproducibility and scalable to 100s mg by employing a CaCl 2 -based eutectic as synthesis medium. Comprehensive characterization confirmed the PHI structure, with Ca 2+ residing in the structural porosity having ionic conductivity of 10 -10 –10 -11 S cm -1 as estimated by electrochemical measurements. In addition to the literature’s physisorption mechanism for dry CO 2 , we demonstrated these Ca 2+ to participate in direct air capture of humid CO 2 , which chemisorbs as CaCO 3 from structural analyses. For photocatalytic CO 2 -to-CO conversion, CaPHI outperforms its K + -bearing counterpart, which we speculatively attributed to strong Ca 2+ –CO 2 interactions that concentrate this reactant near the active sites. In establishing a reliable synthesis and demonstrating its ability for CO 2 capture and photoreduction, further optimization of CaPHI’s structure, morphology and compositing with co-catalyst could reveal its potential for CCC, while incorporation of mobile Ca 2+ may represent a broad design principle warranting future research for material development for improving the efficiency of carbon capture & utilization.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Chemistry, National Cheng Kung University, No. 1 University Road, Tainan City, Taiwan (ROC, 701",
    "Department of Materials Science and Engineering, National Cheng Kung University, No. 1 University Road, Tainan City, Taiwan, 701",
    "Max Planck Institute for Solid State Research, Heisenbergstrasse 1, Stuttgart, Germany, 70569",
    "Department of Chemistry, Ludwig-Maximilian-University Munich, Butenandtstraße 5-13, Munich, Germany, 81377"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 7,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Chi-Chen Chang"
    },
    {
      "affs": [
        1
      ],
      "name": "Hsin-Hui Lin"
    },
    {
      "affs": [
        1
      ],
      "name": "Pin-Yu Shi"
    },
    {
      "affs": [
        2
      ],
      "name": "Stefan Repp"
    },
    {
      "affs": [
        2,
        3
      ],
      "name": "Bettina V. Lotsch"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Wen-Hui Sophia Cheng"
    },
    {
      "affs": [
        0
      ],
      "name": "Vincent Wing-hei Lau",
      "orcid": "0000-0003-4400-6781"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ebyf54xewk83n.bib",
  "cited_by": 0,
  "doi": "10.26434/chemrxiv.15010817/v1",
  "fulltext_url": null,
  "id": "ebyf54xewk83n",
  "issns": [],
  "landing_url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010817/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",
      "2210|Carbon Dioxide Capture Technologies"
    ]
  ],
  "openalex": "W7223184070",
  "pdf_url": "https://chemrxiv.org/doi/pdf/10.26434/chemrxiv.15010817/v1",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-22",
  "publisher": "American Chemical Society (ACS)",
  "ris": "https://research.draconitic.com/paper/ebyf54xewk83n.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:24Z",
      "native_id": "10.26434/chemrxiv.15010817",
      "source": "chemrxiv",
      "url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010817/v2"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "source:chemrxiv",
      "subfield": "general"
    }
  ],
  "title": "Calcium Poly(heptazine imide): Reproducible Synthesis for Structural Analysis, Mechanism of CO ₂ Uptake, and Evaluation of Photocatalytic CO ₂ - to-CO Conversion",
  "title_text": "Calcium Poly(heptazine imide): Reproducible Synthesis for Structural Analysis, Mechanism of CO ₂ Uptake, and Evaluation of Photocatalytic CO ₂ - to-CO Conversion",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:26Z",
  "url": "https://research.draconitic.com/paper/ebyf54xewk83n",
  "venue": "ChemRxiv",
  "versions": []
}