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Li et al. Chem Synth 2023;3:30 https://dx.doi.org/10.20517/cs.2023.16 Page 7 of 17

Figure 1. (A) SEM images and (B) (C) TEM images of MIL-53-800; (D) SEM images and (E) (F) TEM images of MIL-68-800; and (G)
SEM images and (H) (I) TEM images of MIL-100-800.

The detailed pore size and cumulative pore volume distribution of these three selected MOF-derived porous
carbon materials were measured by N desorption-adsorption. The sharp increase of N adsorption at low
2
2
relative pressures (p/p < 0.01) and hysteresis loop in the N adsorption isotherms [Figure 2A] demonstrate
2
0
that all three MOF-derived porous carbon materials contain micropores and mesopores . Compared with
[54]
MIL-53-800 and MIL-68-800, MIL-100-800 has much more micropores but fewer mesopores. The
cumulative pore size distribution of MIL-53-800, MIL-68-800, and MIL-100-800, calculated by the method
of NLDFT, is shown in Figure 2B and converted into a histogram with four size zones in Figure 2C. All
three samples show hierarchically porous structures with various pore sizes at different length scales. Four
kinds of pores can be observed: ultramicropore (< 0.7 nm), supermicropore (0.7-2 nm), small mesopore (2-
10 nm), and big mesopore (10-50 nm). Considering the ultramicropores (< 0.7 nm), the pore volume in this
-1
3
-1
range of MIL-53-800 is 0.15 cm g , which is similar to that of MIL-100-800 (0.16 cm g ) while four times
3
higher than that of MIL-68-800 (0.04 cm g ). For the supermicropores (0.7-2 nm), the pore volume of
3
-1
MIL-53-800 (0.15 cm g ) is comparable to that of MIL-68-800 (0.12 cm g ) and half of that of MIL-100-
-1
3
-1
3
800 (0.33 cm g ). For the small mesopores (2-10 nm), the volume of MIL-53-800 is the biggest (1.21 cm g
3
3
-1
-1 ), which is two and six times higher than that of MIL-68-800 and MIL-100-800, respectively. The big
mesoporous volume (10-50 nm) of MIL-53-800, MIL-68-800, and MIL-100-800 is 0.82, 1.41, and 0.14 cm g
3
-1 , respectively. Due to the three-dimensional trimesic acid ligand, MIL-100-800 shows higher stability with
more micropores, which represents 60% of the total volume. The harsh pyrolysis temperature and acid wash
lead to the formation of high quantities of mesopores in MIL-53-800 and MIL-68-800. The detailed pore
information of these three MIL-(53, 68, and 100)-800, including micropores and mesopores, is shown in
Figure 2D-F. The pore size distribution and value of the pore volume are well consistent with the above-
mentioned results.
For Se@MIL-(53, 68, 100)-800, the composites of Se and corresponding prepared porous carbon materials
with a weight ratio of 2:1 were ball-milled and heated in Ar at 260 °C. The Se was confined by the metal
diffusion method, in which the commercial Se particles were melted to liquid that diffused from micropores