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Li et al. Chem Synth 2023;3:30 https://dx.doi.org/10.20517/cs.2023.16 Page 5 of 17

7500 F field-emission SEM. Transmission electron microscopy (TEM) images of the samples were recorded
on microgrid copper mesh by using a TECNAI 10 at an acceleration voltage of 200 kV. Nitrogen (N )
2
adsorption–desorption isotherms were obtained using an ASAP 2420 surface area & porosity analyzer at 77
K. The specific surface area was calculated by the Brunauer-Emmett-Teller (BET). The pore size
distribution was calculated by the Barrett–Joyner–Halenda (BJH) method and the nonlocal density
functional theory (NLDFT) analysis method. Thermogravimetric analysis (TGA) was carried out using a
thermal analyzer (Setaram Labsys Evo) under a flow of N with a temperature ramp of 5 °C min . X-ray
-1
2
photoelectron spectroscopy (XPS) characterization was carried out in a Thermo Fisher ESCALAB 250 Xi
instrument with a monochromatic Al Kα x-ray source (1486.6 eV). Raman spectra were collected by an
-1
Invia Refl (Renishaw, UK) under ambient conditions, from 2000 to 200 cm with 632.8 nm laser light.

Electrochemical measurements
The electrochemical measurements were carried out at room temperature using CR2032 coin-type cells. The
[40]
cathodes were prepared with a conventional slurry coating method . The slurry was prepared by mixing
the active material, Super-P carbon (Timcal), and sodium alginate (SA, Sigma-Aldrich) at the weight ratio
of 80:10:10 in deionized water. The reference pure Se cathode slurry was prepared by mixing commercial Se,
Super-P carbon, and SA with a weight ratio of 60:30:10. The resulting slurry was coated onto an aluminum
foil and dried in a vacuum at 60 °C one night. The coated aluminum foil was cut into discs with a diameter
of 14 mm to obtain the Se cathode. The mass loading of Se on the cathode is approximately 1.5 mg cm .
-2
The coin-type cells were assembled in an Ar-filled glovebox with moisture and oxygen concentrations lower
than 1 ppm, using Li metal as the counter/reference electrode, glass fiber membrane as the separator, and 1
M Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, Solvay) in a mixture of dioxolane (DOL, Sigma-
Aldrich) and dimethoxygethane(DME, Sigma-Aldrich) (1:1 in volume) with 1% LiNO (Sigma-Aldrich) as
3
the electrolyte. The galvanostatic discharge and charge experiments were performed on a battery tester
+
(LAND) with a voltage window of 1.75-2.6 V vs. Li /Li at different current rates of 0.1, 0.2, 0.5, 1, 2, and 5 C
(1 C = 75 mA g ). Cyclic voltammetry (CV) study (1.75-2.6 V vs. Li /Li, 0.1 mV s ) was performed using an
+
-1
-1
electrochemical workstation Princeton VersaSTAT 3, beginning with discharge at 2.6 V. Electrochemical
impedance spectroscopy (EIS) measurement was also conducted using Princeton VersaSTAT 3 with a
frequency range between 100 kHz and 10 mHz with an AC voltage amplitude of 5 mV at open circuit
voltage.

RESULTS AND DISCUSSION
Structural analysis
Scheme 1 illustrates the preparation process to (A) MIL-53 (Al), (B) MIL-68 (Al), and (C) MIL-100 (Al) and
then to MIL-53-800, MIL-68-800, and MIL-100-800. MIL-53 (Al) (A) and MIL-68 (Al) (B) were synthesized
with the same ligand (TPA) but with different solvents and temperatures, while MIL-100 (Al) (C) was
synthesized with trimesic acid. These three MOFs exhibit fully different pore networks. In the case of MIL-
53 (Al), only one 1D-rhombic type of pore with a size of 0.85 nm is found [Scheme 1A] , while MIL-68
[46]
(Al) exhibits two different types of channels (triangular and hexagonal) with pore sizes of 0.5-0.85 nm and
1.6-1.7 nm, respectively [Scheme 1B] . As for MIL-100 (Al), its framework is formed by channels of
[47]
[48]
micropores and mesopores of around 0.6 and 2.5-2.9 nm in diameter, respectively [Scheme 1C] . The
MOF-derived porous carbon materials were obtained by the calcination of MOFs at high temperature in Ar,
followed by an acid wash to remove aluminum.

The successful synthesis of aluminum-based MOFs, including MIL-53 (Al), MIL-68 (Al), and MIL-100 (Al),
can be confirmed by the powder XRD patterns shown in Supplementary Figure 1. The representative peaks
of MIL-53 (Al), MIL-68 (Al), and MIL-100 (Al) are the same as the simulated peaks, which are consistent
with the previous reports [41-44] . Following the pyrolysis, porous carbon materials are synthesized.