Porphyrin and its derivatives have good photodynamic activity due to their abilities to produce
1O
2 under the light irradiation. To investigate the photodynamic performance of B-PCN-134, L-PCN-134 and S-PCN-134 nanosheets, the commercial singlet oxygen sensor green (SOSG) was chosen to monitor the production of
1O
2. There was almost no fluorescence in the free SOSG solution, while it would exhibit strong green emission with the maximum wavelength of 525 nm in the presence of
1O
2. The final concentration of the B-PCN-134 was kept at 50 µg/mL. After irradiation using a near infrared (NIR) light (660 nm, 0.5 W/cm
2) for 5 min, the fluorescence intensity of the SOSG solution slightly increased (
Fig. 2a), suggesting that B-PCN-134 could generate
1O
2 under the irradiation. As shown in
Fig. 2b, when adding L-PCN-134 nanosheets into the SOSG solution, its fluorescence intensity at 525 nm was 2.5 times higher, compared to that of the B-PCN-134. Promisingly, the fluorescence intensity of SOSG solution in the presence of S-PCN-134 nanosheets was even higher (
Fig. 2c), which was 6.5 times in the comparison with that of B-PCN-134. These results indicated that S-PCN-134 nanosheets had the strongest ability to produce
1O
2. Additionally, the influence of the power of the lamp on the ability of S-PCN-134 nanosheets to produce
1O
2 was also detected. As shown in Fig. S6 (Supporting information), the generation
1O
2 of the S-PCN-134 nanosheets was gradually enhanced with the increasing powder of lamp. Furthermore, electron spin resonance (ESR) spectrum was also used to detect
1O
2 from B-PCN-134, L-PCN-134 and S-PCN-134 using 2, 2, 6, 6-tetramethylpiperidine (TEMP) as the spin trapping agent. It can be seen that the amplitude of ESR peaks in the B-PCN-134 is very limited under the illumination for 5 min in the comparison to that of free TEMP (
Fig. 2d), indicating that the
1O
2 production of B-PCN-134 is very low. As for the PCN-134 nanosheets, the ESR signal of both L-PCN-134 (
Fig. 2e) and S-PCN-134 (
Fig. 2f) are obviously stronger than those of bulk under the same irradiation condition. Promisingly, the ESR signal of the S-PCN-134 nanosheets is the strongest among the three MOFs with different size, further revealing that the S-PCN-134 nanosheets exhibit the strongest ability to generate
1O
2 under light irradiation.