Disentangling the complex photodynamics of mixed-linker Zr-MOFs – efficient energy and charge transfer processes

Abstract

Controlling the composition and defects in metal-organic frameworks (MOFs) helps in the understanding of the interactions that govern their behaviours, and in consequence, their potential employment in a number of...

Unraveling the Optimal Cerium Content for Boosting the Photoresponse Activity of Mixed-Metal Zr/Ce-Based Metal–Organic Frameworks through a Photodynamic and Photocurrent Correlation: Implications on Water Splitting Efficiency

“…Similarly, the photodynamic properties of these MOFs are affected by the content of Ce. As previously reported, the photodynamics of the pristine Zr-NDC MOF shows a multiexponential behavior attributed to the emission lifetimes of NDC monomers and excimers along with a shorter component ascribed to the excimer photoformation. − The observed trend in the photodynamics of the MOFs studied here is a decrease in the lifetime values with the content of Ce as a consequence of a more efficient LCCT due to the better overlap of the linker and Ce orbitals. In fact, the study of the nonradiative photoprocesses of these MOFs demonstrates the existence of an ultrafast LCCT process, leading to the formation of long-lived (microsecond regime) CSSs.…”

“…Consequently, the doping of the Zr clusters with Ce atoms enhances the orbital overlap with the naphthalene linkers, as explained above, and therefore, the LCCT becomes more favored. Since the LCCT is an ultrafast process, ,, an increase in the efficiency of this phenomenon induces a decrease in the value of the risetime, as this value will be a combination of both processes. In addition, the decrease in the lifetime of the NDC monomers (from 7.0 to 3.2 ns) further corroborates the opening of additional nonradiative deactivation channels.…”

“…The TAS are characterized by a continuous negative band spanning from 700 to 400 nm, typical of systems having long-lived CSSs, as reported for several other MOFs. 30,34,44,45,60,61 Interestingly, the TA intensity increases with the content of Ce in the MOFs up to NDC-Ce (9) and then it shows a slight decrease for the NDC-Ce (12). As the experimental conditions (concentration of the samples, excitation wavelength and power, temperature, etc.)…”

“…In agreement with previous reports on Zr-NDC MOFs, we assign the bands at 500 and 900 nm to the absorption of the excited NDC linkers and to the CSS produced following the LCCT reaction, respectively. 44,45 To further characterize the ultrafast dynamics of the studied samples, we analyzed the transient decays collected at 900 nm (Figure 4C,D). The transients were fitted satisfactorily by a bi-(DCM) or triexponential (DMF) function (Table 2).…”