Atomic-scale origin of charge density wave-driven metal-semiconductor transition in an incommensurately modulated metal-organic framework

Bin Jiang; Chao Zhang; Guobao Li; Hao Chen; Hongli Jia; Huimin Qi; Jian Wang; Jiaxiang Zhang; Jin-Hu Dou; Jinkun Guo

arxiv: 2604.19640 · v1 · submitted 2026-04-21 · ❄️ cond-mat.mtrl-sci · cond-mat.mes-hall

Atomic-scale origin of charge density wave-driven metal-semiconductor transition in an incommensurately modulated metal-organic framework

Ling Zhang , Zeyue Zhang , Liu He , Bin Jiang , Yingchao Wang , Jiaxiang Zhang , Huimin Qi , Chao Zhang

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Jinkun Guo Hao Chen Yunlong Fan Yanran Shen Hongli Jia Guobao Li Yu-Qing Zheng Julius J. Oppenheim Tianyang Chen Jian Wang Lei Sun Junliang Sun Jin-Hu Dou

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Pith reviewed 2026-05-10 01:51 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci cond-mat.mes-hall

keywords metal-organic frameworkcharge density waveincommensurate modulationmetal-semiconductor transitionsingle-crystal X-ray diffractionguest moleculesPr3HHTP2

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The pith

The lattice modulation in Pr3HHTP2 vanishes at the same temperature as its metal-to-semiconductor transition, showing the distortion is driven by a charge density wave.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper resolves the incommensurately modulated atomic structure of a conductive metal-organic framework at low temperature and demonstrates that the modulation disappears exactly when the material undergoes a reversible metal-semiconductor transition near 350 K. The precise synchronization supplies direct evidence that the lattice distortion originates from electronic instability rather than a separate structural mechanism. Guest water molecules stabilize the modulated phase by controlling linker rotations and interlayer spacing to optimize inter-linker interactions. The work supplies an experimental benchmark for identifying one-dimensional charge density waves in metal-organic frameworks and a platform for studying how electronic and lattice degrees of freedom couple in these materials.

Core claim

Single-crystal X-ray diffraction on Pr3HHTP2 at 100 K yields the modulation vector q = 0.39143(12) c*. A reversible metal-semiconductor transition occurs around 350 K and coincides exactly with the disappearance of this structural modulation. The authors conclude that the incommensurate lattice distortion is therefore of electronic origin, with guest water molecules acting to stabilize the modulated phase through synergistic adjustment of linker rotation and interlayer spacing.

What carries the argument

The exact temperature coincidence between the loss of the incommensurate structural modulation (q = 0.39143(12) c*) and the metal-semiconductor transition, which serves as the diagnostic linking the distortion to charge-density-wave formation.

If this is right

The result supplies a concrete experimental criterion for recognizing one-dimensional charge density waves in metal-organic frameworks.
It creates an ideal platform for investigating coupled electronic-lattice modulations in conductive hybrid materials.
Guest molecules can be used to tune the stability range of the modulated phase by altering linker rotation and interlayer spacing.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

Replacing or removing the guest water could shift the transition temperature and thereby test the proposed stabilization mechanism.
The same synchronization signature might be sought in other layered MOFs with similar linker geometries to identify additional CDW candidates.
The finding suggests routes to engineer temperature-tunable electronic switches in MOFs by selecting metals and linkers that control CDW onset.

Load-bearing premise

That the observed coincidence in transition temperature demonstrates the structural modulation is caused by electronic instability rather than two independent phenomena simply sharing the same temperature.

What would settle it

A direct probe of the electronic band structure, such as angle-resolved photoemission or optical spectroscopy, showing whether a gap opens at the Fermi surface exactly when the modulation appears below 350 K.

read the original abstract

The intrinsic incommensurate charge density wave in metal-organic frameworks has remained elusive due to the lack of direct evidence linking atomic-scale structural modulation to macroscopic electronic properties. Using high-quality Pr3HHTP2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) single crystals as a model system, we precisely resolve, for the first time, the incommensurately modulated structure of a conductive metal-organic framework at 100 K (modulation vector q = 0.39143(12) c*) via temperature-dependent single-crystal X-ray diffraction. The subsequent observation of a reversible metal-semiconductor transition around 350 K, which perfectly synchronizes with the disappearance of the structural modulation, provides convincing evidence for the electronic origin of the lattice distortion. Guest water molecules stabilize the modulated phase by synergistically regulating the relative rotation of the linkers and the interlayer spacing, thereby optimizing the inter-linker interactions. This work establishes a concrete experimental criterion for one-dimensional charge density wave in metal-organic frameworks and provides an ideal platform for probing coupled electronic-lattice modulations.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

They resolve the incommensurate modulation vector in this MOF with single-crystal XRD and show it vanishes at the same temperature as the metal-semiconductor transition, but guest-water stabilization makes the CDW claim hard to sustain without more evidence.

read the letter

The main thing to know is that this paper gives the first atomic-scale resolution of an incommensurate structural modulation in a conductive MOF, with a specific q vector from temperature-dependent single-crystal XRD on Pr3HHTP2 crystals, and links its disappearance around 350 K to the point where transport switches from metallic to semiconducting behavior on the same samples. That direct synchronization is the clearest new experimental result here. Prior MOF CDW reports apparently lacked this level of structural precision tied to transport data. The work does a solid job on the diffraction side, pinning down q = 0.39143(12) c* at 100 K and tracking how the modulation fades with temperature. That kind of matched dataset is useful for anyone trying to connect lattice distortions to electronic changes in these frameworks. The guest-water role is the soft spot. The abstract states that water molecules stabilize the modulated phase by tuning linker rotations and interlayer spacing to optimize interactions. This points to a structural or host-guest mechanism, so the temperature coincidence could simply mark when those interactions break down rather than proving an electronic driving force like Fermi-surface nesting. No calculations or spectroscopy are referenced to show an independent electronic instability at that q, which leaves the CDW interpretation resting on timing alone. The structural observations still stand on their own. This is the sort of paper that researchers working on conductive MOFs or low-dimensional modulations would want to read and discuss. The data merits a serious referee process even if the driving-force discussion needs tightening.

Referee Report

2 major / 2 minor

Summary. The manuscript reports the atomic-scale structure of the conductive MOF Pr3HHTP2 via temperature-dependent single-crystal X-ray diffraction, resolving an incommensurate modulation (q = 0.39143(12) c*) at 100 K. It describes a reversible metal-semiconductor transition near 350 K that coincides with the loss of this modulation, interpreting the synchronization as evidence that the lattice distortion is electronically driven (a charge density wave). Guest water molecules are stated to stabilize the modulated phase by regulating linker rotation and interlayer spacing.

Significance. If the central claim is upheld, the work would establish the first direct experimental connection between incommensurate structural modulation and electronic transport in a MOF, supplying a concrete criterion for identifying one-dimensional CDW behavior in these materials. The use of high-quality single crystals enabling precise q-vector determination and the observation of a reversible, synchronized transition are clear strengths that advance the field beyond prior indirect reports.

major comments (2)

[Abstract] Abstract: The statement that the ~350 K metal-semiconductor transition 'perfectly synchronizes with the disappearance of the structural modulation' and thereby 'provides convincing evidence for the electronic origin of the lattice distortion' is load-bearing for the central claim yet is not adequately supported. The same abstract notes that 'Guest water molecules stabilize the modulated phase by synergistically regulating the relative rotation of the linkers and the interlayer spacing.' This opens a plausible alternative that the transition reflects guest desorption or thermal disruption of the same structural interactions that produce the modulation, rather than an electronic instability. No independent signature (Fermi-surface nesting, soft-mode calculation at the observed q, or spectroscopic gap) is referenced to resolve the degeneracy.
[Results/Discussion] Results/Discussion (transport and diffraction sections): The manuscript provides no controls for guest-molecule removal (e.g., TGA, in-situ mass spectrometry, or transport measurements under sealed vs. open atmosphere) and does not report error bars or statistical assessment of the precise coincidence between the structural and electronic transitions. Without these, it is impossible to exclude that both phenomena are driven by the same guest-related structural change rather than by CDW physics.

minor comments (2)

[Methods] The modulation vector is reported to five decimal places in q; the refinement section should explicitly state the number of independent reflections, R-factors for the modulated vs. average structure, and how the incommensurate component was extracted from the diffraction data.
[Figures and text] Figure captions and text should clarify whether the transport data were collected on the same crystals used for the XRD study or on separate batches, and whether any hysteresis was observed in the heating/cooling cycles.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive and detailed comments. These have prompted us to strengthen the manuscript by moderating claims, adding controls, and clarifying the interpretation of the observed coincidence. We respond point by point below.

read point-by-point responses

Referee: [Abstract] Abstract: The statement that the ~350 K metal-semiconductor transition 'perfectly synchronizes with the disappearance of the structural modulation' and thereby 'provides convincing evidence for the electronic origin of the lattice distortion' is load-bearing for the central claim yet is not adequately supported. The same abstract notes that 'Guest water molecules stabilize the modulated phase by synergistically regulating the relative rotation of the linkers and the interlayer spacing.' This opens a plausible alternative that the transition reflects guest desorption or thermal disruption of the same structural interactions that produce the modulation, rather than an electronic instability. No independent signature (Fermi-surface nesting, soft-mode calculation at the observed q, or spectroscopic gap) is referenced to resolve the degeneracy.

Authors: We agree that the original abstract wording overstated the conclusiveness of the evidence. The observed synchronization between the loss of the incommensurate modulation and the metal-semiconductor transition is correlative and does not by itself constitute definitive proof of an electronically driven CDW. In the revised manuscript we will change the abstract to state that the coincidence 'suggests' an electronic contribution to the lattice distortion while explicitly noting the stabilizing role of guest water. We will also expand the discussion section to address the alternative guest-desorption scenario, emphasizing that the transition is fully reversible over multiple thermal cycles (as shown in the transport data), which is inconsistent with irreversible water loss. Regarding independent signatures, we acknowledge their absence; soft-mode calculations and ARPES are technically demanding for these air-sensitive MOF crystals and lie outside the present scope. We will add a short paragraph outlining why such measurements are challenging and how the current atomic-resolution structural data plus transport correlation still provide a useful experimental benchmark for CDW behavior in MOFs. revision: partial
Referee: [Results/Discussion] Results/Discussion (transport and diffraction sections): The manuscript provides no controls for guest-molecule removal (e.g., TGA, in-situ mass spectrometry, or transport measurements under sealed vs. open atmosphere) and does not report error bars or statistical assessment of the precise coincidence between the structural and electronic transitions. Without these, it is impossible to exclude that both phenomena are driven by the same guest-related structural change rather than by CDW physics.

Authors: We accept that additional controls are needed to strengthen the exclusion of guest-driven artifacts. In the revised version we will include thermogravimetric analysis (TGA) data demonstrating that guest water remains stable up to at least 400 K under the conditions used for diffraction and transport. We will also add transport curves recorded under inert atmosphere and compare them with ambient measurements to confirm the transition is intrinsic. For the temperature coincidence, we will report error bars on both the structural (from multiple crystals) and electronic transition temperatures, together with a brief statistical note on the overlap within the experimental resolution of the diffractometer and cryostat. revision: yes

Circularity Check

0 steps flagged

No circularity in experimental chain

full rationale

The paper's central claim rests on direct experimental measurements: temperature-dependent single-crystal X-ray diffraction resolving the incommensurate modulation (q = 0.39143(12) c*) at 100 K and its disappearance coinciding with a reversible metal-semiconductor transition near 350 K. No equations, fitted parameters, or derivations are presented that reduce by construction to inputs defined within the work. The additional note on guest water molecules stabilizing the modulated phase via structural regulation is an independent observational finding, not a self-referential input used to force the electronic-origin conclusion. The logic is self-contained against external benchmarks of diffraction and transport data.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on standard crystallographic assumptions about diffraction data interpretation and on the interpretation that the observed modulation constitutes a charge-density wave. No explicit free parameters are introduced in the abstract. No new particles or forces are postulated.

axioms (2)

standard math Single-crystal X-ray diffraction patterns can be indexed to an incommensurate modulation vector q = 0.39143(12) c* at 100 K.
Invoked when reporting the resolved structure; standard in crystallography but requires high-quality data and proper refinement.
domain assumption Disappearance of the modulation at ~350 K is the cause of the metal-semiconductor transition rather than a correlated but independent phenomenon.
The synchronization is presented as evidence for electronic origin; this causal step is an assumption not directly proven by the measurements alone.

pith-pipeline@v0.9.0 · 5588 in / 1498 out tokens · 44329 ms · 2026-05-10T01:51:54.660382+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

1 extracted references · 1 canonical work pages

[1]

Acta Crystallogr., Sect

1 IUCr. Acta Crystallogr., Sect. A: Found. Crystallogr. 48, 922–946 (1992). 2 Janssen, I., Janner, A., Looijenga-Vos, A. & De Wolff, P. M. 9.8. Incommensurate and commensurate modulated structures. . International Tables for Crystallography, 907-913 (2006). 3 Oftedahl, P. et al. Higher dimensionality in the Mg-Co-B system: synthesis and structure of incom...

work page doi:10.1021/jacs.5c21952 1992

[1] [1]

Acta Crystallogr., Sect

1 IUCr. Acta Crystallogr., Sect. A: Found. Crystallogr. 48, 922–946 (1992). 2 Janssen, I., Janner, A., Looijenga-Vos, A. & De Wolff, P. M. 9.8. Incommensurate and commensurate modulated structures. . International Tables for Crystallography, 907-913 (2006). 3 Oftedahl, P. et al. Higher dimensionality in the Mg-Co-B system: synthesis and structure of incom...

work page doi:10.1021/jacs.5c21952 1992