Metal–organic frameworks (MOFs) show great prospect as catalysts and catalyst support materials. Yet, studies that address their dynamic, kinetic, and mechanistic role in target reactions are scarce. In this study, an exceptionally stable MOF catalyst consisting of Pt nanoparticles (NPs) embedded in a Zr-based UiO-67 MOF was subject to steady-state and transient kinetic studies involving H/D and 13C/12C exchange, coupled with operando infrared spectroscopy and density functional theory (DFT) modeling, targeting methanol formation from CO2/H2 feeds at 170 °C and 1–8 bar pressure. The study revealed that methanol is formed at the interface between the Pt NPs and defect Zr nodes via formate species attached to the Zr nodes. Methanol formation is mechanistically separated from the formation of coproducts CO and methane, except for hydrogen activation on the Pt NPs. Careful analysis of transient data revealed that the number of intermediates was higher than the number of open Zr sites in the MOF lattice around each Pt NP. Hence, additional Zr sites must be available for formate formation. DFT modeling revealed that Pt NP growth is sufficiently energetically favored to enable displacement of linkers and creation of open Zr sites during pretreatment. However, linker displacement during formate formation is energetically disfavored, in line with the excellent catalyst stability observed experimentally. Overall, the study provides firm evidence that methanol is formed at the interface of Pt NPs and linker-deficient Zr6O8 nodes resting on the Pt NP surface.

With the purpose of understanding the behavior of aluminosilicate zeolites and silicoaluminophosphates (SAPOs) in the presence of steam, we carried out a computational density functional theory (DFT) study on the desilication of SAPO-34. The mechanism studied was a stepwise hydrolysis of the four bonds to the Si heteroatom. An analogous process to the desilication of SAPO-34 is the dealumination of SSZ-13. To investigate possible mechanistic differences between the two processes, we compared the results of this study with the results of a previous study on dealumination in SSZ-13. We found that the intermediates along the dealumination path of SSZ-13 have one of the protons bonded to a bridging oxygen atom. In the corresponding intermediates of the desilication path in SAPO-34, the same proton prefers to be part of an aqua ligand coordinated to an Al atom. The principal factor determining the different proton locations is the electronic requirement of the atoms surrounding the proton. The different proton locations in SSZ-13 and SAPO-34 put clear conditions on possible mechanisms, thus causing them to be different for the two materials. We expect the principles determining the proton location also to be valid for other mechanisms of dealumination in SSZ-13 and desilication in

The energy ordering of configurations, with 6 among the 10 V centers reduced, is predicted using 3 easily accessible variables.

With the aim of understanding the desilication of SAPO-34, we compared three different reaction mechanisms for the hydrolysis of framework silicon by use of density functional theory (DFT) calculations. All three mechanisms are characterized by stepwise hydrolyses of Si–O–Al bonds. In the most favorable mechanism water molecules adsorb strongly to the Lewis acidic Al atoms neighboring the Si atom. Furthermore, evaluation of free energies reveals that an additional water molecule may catalyze the hydrolysis of the first Si–O–Al bond.