DOI: 10.5061/dryad.rxwdbrvqg
title: Molecular solar thermal energy storage in Dewar Pyrimidone beyond 1.6 MJ/kg

description: Storing sunlight in a compact and rechargeable form remains a central
 challenge for solar energy utilization. Molecular solar thermal (MOST)
 energy storage systems, which harness photon energy and release it as heat
 on demand, provide a direct approach, but have long failed to meet
 practical benchmarks. Inspired by the architecture of DNA, we report a
 pyrimidone-based MOST system that stores energy in the strained Dewar
 photoisomer upon excitation at 300 nm. Designed with sustainability in
 mind, the system operates solvent-free and remains compatible with aqueous
 environments while overcoming one of the field’s greatest hurdles: the
 controlled extraction and transfer of stored heat. When catalyzed by acid,
 the Dewar isomer releases enough heat to boil water (~0.5 mL). These
 advances help point the way toward decentralized solar heat storage and
 off-grid energy solutions.
description: # Molecular solar thermal energy storage in Dewar Pyrimidone beyond 1.6
 MJ/kg Dataset DOI:
 [10.5061/dryad.rxwdbrvqg](https://doi.org/10.5061/dryad.rxwdbrvqg) ##
 **Author information** Corresponding author: Grace G. D. Han
 ([grace_han@ucsb.edu](mailto:grace_han@ucsb.edu))^1,2^, K. N. Houk
 ([houk@ucla.edu](mailto:houk@ucla.edu))^3^ ^1^Department of Chemistry and
 Biochemistry, University of California, Santa Barbara, CA, 93016 USA.
 ^2^Department of Chemistry, Brandeis University, Waltham, MA, 02453 USA.
 ^3^Department of Chemistry and Biochemistry, University of California, Los
 Angeles, CA, 90095-156 USA. ## **Description of the data and file
 structure** This supplementary dataset supports our study on a
 pyrimidone-based molecular solar thermal (MOST) energy storage system. The
 dataset includes: * UV–Vis spectroscopy datasets (Files 1–5): solution,
 thin-film, and cycling studies in DMSO and water * Photoisomerization
 quantum yield study (File 6) * Thermal reversion kinetics study (File 7) *
 Photoluminescence study (File 8) * DSC thermograms of pyrimidones and
 Dewar isomers (Files 9–10) * TGA profiles of pyrimidones (File 11) *
 Energy density comparison dataset (File 12) * IR thermal imaging
 heat-transfer experiments (File 13) ### **Notes** * Units are included in
 the headers and/or variable descriptions. * Experimental details are
 provided in the associated **Main Text** and **Supplementary Materials**.
 * Some files contain multiple experimental blocks within one CSV file; all
 column headers are uniquely labeled for repository compatibility. ##
 **Files and variables** **File: 1_UV-Vis_P1-to-P4_310nm.csv**
 **Description:** UV–Vis spectral changes upon photoisomerization of
 Pyrimidones **1**–**4** in HPLC-grade acetonitrile under 310 nm
 irradiation.\ **Variables:** * wavelength (nm) * abs (a.u.) * normalized
 abs (a.u.)  **File: 2_UV-Vis_P-4_thin-film_310nm.csv** **Description:**
 UV–Vis absorption spectra from the thin-film irradiation experiment at 310
 nm for P-**4**.\ **Variables:** * wavelength (nm) * abs (a.u.) *
 normalized abs (a.u.)  **File: 3_UV-Vis_D2-to-D4_95C.csv**
 **Description:** UV–Vis absorption spectra of Dewars **2**–**4** in DMSO
 upon heating at 95 °C.\ **Variables:** * wavelength (nm) * abs (a.u.) *
 normalized abs (a.u.)  **File: 4_UV-Vis_P-3_Cycling-in-Water.csv**
 **Description:** UV–Vis cycling study for P-**3** in water. P-**3** was
 irradiated to form D-**3**, then acidified to regenerate pyrimidone in its
 salt form (P-**3**^+^). A second cycle includes neutralization with
 NaHCO~3~, irradiation, and re-acidification to reform P-**3**^+^.\
 **Variables:** * wavelength (nm) * abs (a.u.) * normalized abs (a.u.)
  **File: 5_Cycling-study_P-3.csv** **Description:** Multi-cycle reversible
 isomerization study of D-**3** in DMSO induced by thermal treatment and
 subsequent irradiation.\ **Variables:** * cycle * abs (a.u.) * normalized
 abs (a.u.)  **File: 6_Quantum-yield_P1-to-P4_310nm.csv** **Description:**
 Kinetics for the photoisomerization of Pyrimidones **1**–**4** in degassed
 HPLC-grade acetonitrile at 293 K under 310 nm irradiation. Absorbance was
 tracked as a function of time.\ **Variables:** * time (s) * abs (a.u.)
  **File: 7_Thermal-kinetics_D2-to-D4_85C-90C-95C.csv** **Description:**
 Thermal reversion kinetics of Dewars **2**–**4** to Pyrimidones
 **2**–**4** in DMSO at 85 °C, 90 °C, and 95 °C. Data were fitted to
 exponential functions and used for Eyring and Arrhenius analysis.\
 **Variables:** * time (s) * abs (a.u.) * 1/T * R0 = k * ln(k/T) * ln(k)
  **File: 8_Photoluminescence-study_P-3.csv** **Description:** Absorbance
 and photoluminescence data for five concentrations of P-**3** and the
 reference dye 2-aminopyridine (2-AP), including acetonitrile emission
 background.\ **Variables:** * wavelength (nm) * abs (a.u.) * intensity
  **File: 9_DSC_P1-to-P4.csv** **Description:** DSC thermograms of
 Pyrimidones **1**–**4** measured during heating/cooling cycles (1^st^
 heating → 1^st^ cooling → 2^nd^ heating).\ **Variables:** * temperature
 (°C) * heat flow (W/g)  **File: 10_DSC_D1-to-D4.csv** **Description:** DSC
 thermograms of Dewars **1**–**4** measured during heating/cooling cycles
 (1^st^ heating → 1^st^ cooling → 2^nd^ heating).\ **Variables:** *
 temperature (°C) * heat flow (W/g)  **File: 11_TGA_P1-to-P4.csv**
 **Description:** TGA data for Pyrimidones **1**–**4**.\ **Variables:** *
 temperature (°C) * weight (mg) * weight (%)  **File:
 12_Energy-density-of-MOST_MJoverkg.csv** **Description:** Gravimetric
 energy densities (MJ/kg) of Dewars **1**–**4** compared with prior MOST
 photoswitches, as shown in **Fig. 2B**. The associated references are
 provided in the main text.\ **Variables:** * gravimetric energy density
 (MJ/kg)  **File: 13_IR-study_expt1-to-expt5.csv** **Description:**
 Temperature profiles from IR thermal imaging experiments **1**–**5**.
 Temperatures were extracted from the hottest pixel (hot spot) on the
 surface of the solution.\ **Variables:** * time (s) * temperature (°C)