MOFs side chains as sources of supramolecular interactions: organic pollutants extraction from water

Polyethylene glycol modified terphenyl tetracarboxylate ligands was used for the preparation of copper based MOFs: SUM-102 and SUM-103. The influence of side chains on the stability and adsorption capacities was...


Characterization of MOF's Crystal Structure Report for e4763
A specimen of C14H15CuO7 was used for the X-ray crystallographic analysis. The X-ray intensity data were measured.
The final anisotropic full-matrix least-squares refinement on F2 with 107 variables converged at R1 = 8.65%, for the observed data and wR2 = 26.80% for all data. The goodness-of-fit was 0.882. The largest peak in the final difference electron density synthesis was 1.440 e-/Å3 and the largest hole was -1.076 e-/Å3 with an RMS deviation of 0.326 e-/Å3. On the basis of the final model, the calculated density was 0.103 g/cm3 and F(000), 368 e-.

Methylene Blue adsorption
The adsorption capacity of MB was calculated based on Equation (1) a-c . The equilibrium adsorption capacity of adsorbent was calculated using Equation (2) c . Q t = (C o − C t ) . V/m (1) Q e = (C o − C e ) . V/m (2) where Q t and C t define the adsorption capacity of the adsorbent (mg/g) and the adsorbate concentration (mg/L), respectively. V represents the volume of adsorbate solution and m the mass of MOF adsorbent. Likewise, Q e and C e define the adsorption capacity of adsorbent and adsorbate concentration (mg/L), respectively, at the equilibrium conditions. The MB isotherms (SI*) were fitted with Langmuir and Freundlich models in order to calculate the maximal adsorption capacity and get insights about the nature of the adsorption. Linear form of Langmuir equation is expressed as indicated below: (3)

= 1 +
Ce is the equilibrium concentration, Qe is equilibrium uptake capacity. K L and Q m are obtained from the slope and the intercept of C e /Q e vs Q e plot. R 2 of the linear plot is 0.9992 which shows applicability of this model. Besides, the separation factor-R L is calculated with Eq (4).
(4) = 1 1 + C m is maximal initial concentration of methylene blue. The R L shows favorability of adsorption. The value between 0 and 1 shows good adsorption.
To fit the data to Freundlich model the Eq (5) was used: To find K F and 1/n (adsorption constants), the plot of lnQ e vs lnCe were drawn. R 2 is 0.7507 which doesn't show a good agreement of this model. The values of adsorption constants for both isotherms are summarized in Table 1. In order to properly describe the adsorption process, two popular methods for studying the adsorption kinetics were applied: Pseudo-first order (PFO) and pseudo second order (PSO). Linear equation of PFO (6) and PSO (7) could be expressed as below: = + 1 2 2 Q e and Q t are the amounts of methylene blue adsorbed (mg/g) on MOFs at equilibrium and at the time t. k 1 (min -1 ) and k 2 (g/mgmin) are the rate constants of PFO and PSO, respectively.