Framework Connectivity Tunes the Nuclear Spin Bath and Extends Coherence in Cu(II) Metal–Organic Framework Qubit Lattices
7 affiliations
- 1Department of Chemistry and Biochemistry
- 2University of Texas at El Paso
- 3Department of Physics & Astronomy, University of Utah, 115S, 1400E, Salt Lake City, UT, 84112
- 4Center for Integrated Nanotechnologies, Sandia National Laboratories
- 5Department of Materials Science and Engineering
- 6University of Florida
- 7Bruker Biospin Corporation
Abstract
Designing solid-state spin-qubit arrays that retain long coherence at high spin density remains a central challenge in quantum information materials. In molecular qubits, this challenge arises because the same local coordination environment and lattice architecture that define the spin array also control the dominant decoherence channels, most notably nuclear-spin spectral diffusion and coupling to low-frequency phonons. Metal–organic frameworks (MOFs) are therefore especially attractive because they combine dense, crystalline spin arrays with chemically programmable control over the coordination environment, framework connectivity, and supramolecular packing, yet a fundamental understanding of how specific structural changes translate into predictable relaxation behavior remains underdeveloped. Here we compare two closely related oxygen-coordinated Cu(II) frameworks, Cu-TPTC and Cu-TPTriC, that preserve the same first-sphere donor set while changing connectivity and supramolecular packing. Cu-TPTC comprises one-dimensional Cu–O chains assembled into hydrogen-bonded rods, whereas Cu-TPTriC forms coordination-connected Cu–O–Cu two-dimensional sheets that stack through interlayer aromatic contacts in the absence of hydrogen-bond stitching. Continuous-wave electron paramagnetic resonance (CW-EPR) spectroscopy shows that both lattices exhibit relatively narrow linewidths compared with a Cu–N porphyrinic benchmark, consistent with reduced ligand-derived superhyperfine broadening in an oxygenonly coordination sphere. Pulsed electron paramagnetic resonance measurements establish coherent spin control and reveal systematically longer spin–lattice relaxation times (T1) and phase-memory times (Tm) in Cu-TPTriC over 5–25 K, with Tm≈4.8 ± 0.011 μs at 5 K. This coherence gain persists despite substantially shorter Cu···Cu separations in Cu-TPTriC and is consistent with a reduced proton-bath density and modified lattice dynamics, as reflected in the weaker electron spin echo envelope modulation (ESEEM) observed for Cu-TPTriC. Together, these results suggest that within dense oxygen-coordinated Cu(II) framework lattices, the secondary-sphere nuclear-spin environment and lattice dynamics can play an important role in governing decoherence, potentially outweighing spin spacing alone.
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BibTeX
@misc{saini2026framework,
title = {{Framework Connectivity Tunes the Nuclear Spin Bath and Extends Coherence in Cu(II) Metal–Organic Framework Qubit Lattices}},
author = {Kavish Saini and Sisheed Sivaraman and Prashanna Poudel and Bonaventure A. Odeke and Gajadhar Joshi and Manny de Jesus Lopez and Alvaro Montoya and Kalina Ranguelova and C. Thomas Harris and Ezra Bussmann and Christoph Boehme and Sreeprasad T Sreenivasan},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15009351/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009351/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Framework Connectivity Tunes the Nuclear Spin Bath and Extends Coherence in Cu(II) Metal–Organic Framework Qubit Lattices
AU - Kavish Saini
AU - Sisheed Sivaraman
AU - Prashanna Poudel
AU - Bonaventure A. Odeke
AU - Gajadhar Joshi
AU - Manny de Jesus Lopez
AU - Alvaro Montoya
AU - Kalina Ranguelova
AU - C. Thomas Harris
AU - Ezra Bussmann
AU - Christoph Boehme
AU - Sreeprasad T Sreenivasan
PY - 2026
DA - 2026/09/23
PB - ChemRxiv
DO - 10.26434/chemrxiv.15009351/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009351/v1
AB - Designing solid-state spin-qubit arrays that retain long coherence at high spin density remains a central challenge in quantum information materials. In molecular qubits, this challenge arises because the same local coordination environment and lattice architecture that define the spin array also control the dominant decoherence channels, most notably nuclear-spin spectral diffusion and coupling to low-frequency phonons. Metal–organic frameworks (MOFs) are therefore especially attractive because they combine dense, crystalline spin arrays with chemically programmable control over the coordination environment, framework connectivity, and supramolecular packing, yet a fundamental understanding of how specific structural changes translate into predictable relaxation behavior remains underdeveloped. Here we compare two closely related oxygen-coordinated Cu(II) frameworks, Cu-TPTC and Cu-TPTriC, that preserve the same first-sphere donor set while changing connectivity and supramolecular packing. Cu-TPTC comprises one-dimensional Cu–O chains assembled into hydrogen-bonded rods, whereas Cu-TPTriC forms coordination-connected Cu–O–Cu two-dimensional sheets that stack through interlayer aromatic contacts in the absence of hydrogen-bond stitching. Continuous-wave electron paramagnetic resonance (CW-EPR) spectroscopy shows that both lattices exhibit relatively narrow linewidths compared with a Cu–N porphyrinic benchmark, consistent with reduced ligand-derived superhyperfine broadening in an oxygenonly coordination sphere. Pulsed electron paramagnetic resonance measurements establish coherent spin control and reveal systematically longer spin–lattice relaxation times (T1) and phase-memory times (Tm) in Cu-TPTriC over 5–25 K, with Tm≈4.8 ± 0.011 μs at 5 K. This coherence gain persists despite substantially shorter Cu···Cu separations in Cu-TPTriC and is consistent with a reduced proton-bath density and modified lattice dynamics, as reflected in the weaker electron spin echo envelope modulation (ESEEM) observed for Cu-TPTriC. Together, these results suggest that within dense oxygen-coordinated Cu(II) framework lattices, the secondary-sphere nuclear-spin environment and lattice dynamics can play an important role in governing decoherence, potentially outweighing spin spacing alone.
ER -