Fig. 4: Adsorption and separation of uranium by the composite photoisomerized MOFs.

a Variation in the maximum adsorption capacity with pH for ZIF-70, PSZ-70, ZIF-60, and PSZ-60. b Adsorption isotherms of two substrate MOFs and their corresponding photoisomeric composites at 298 K. c Visualization of ion swimming by different substrate pore sizes of MOFs. d Comparison of the maximum adsorption capacity of uranium by the photoisomerization process of PSZ-70 and PSZ-60. e Photoisomerization fatigue test under alternate UV-Vis exposure cycles (Purple color indicates the absorbance measurements under UV irradiation, yellow color indicates the absorbance measurements under visible light irradiation, and the bar widths do not correlate with the measurement duration. Number-close indicates the number of times the photoswitch was in the closed state during the five cycles test (i.e., the photoswitch was in the closed state for the nth time (n = 1, 2, 3, 4, 5)), and this description also applies to the open state). f Adsorption selectivity of PSZ-70 and PSZ-60 with their corresponding open/closed isomeric states for some metal cations in simulated seawater systems. g Test of the separability of uranium and vanadium by in situ photocontrolled reversible isomerization. h Comparison of the maximum adsorption capacities and U(VI)/V(V) separation ratios of photoisomerized MOFs with adsorbent materials in some of the similar experimental systems. i PSZ-70 and PSZ-60’s adsorption abilities in fully open and closed conformations in natural seawater with uranium spikes. Error bars in Fig. 4b and i represent standard deviations (SD) calculated from three independent replicate experiments for each data point, the SD was computed to reflect the variability of the measurements.