Mimicking a biocatalytic system has been one of the prevalent strategies for the design of novel and efficient chemical transformations. Among the enzyme-catalyzed reactions, the cooperative interplay of Lewis- and Brønsted-acidic functionalities at active sites represents a common feature in activating reactants. Employing MIL-101(Cr) as a biomimetic platform, we customize a sulfonic group (SO3H) into its hierarchical pores to generate a heterogeneous catalyst for transfer hydrogenation of imines by using Hantzsch ester as the reductant. Both aldimines and ketimines were efficiently converted to their hydrogenated counterparts in a manner similar to metal enzymes. The Cr3+ node and sulfonic acid functionality encapsulated in MOF cages worked cooperatively in promoting this transformation, resulting in an enhanced reactivity as compared to its homogeneous analogue. Furthermore, MIL-101(Cr)-SO3H could be recycled for many times without considerable loss in reactivity.

A series of Cr-terephthalates metal-organic frameworks functionalized by sulfonic acid group (?SO3H) [MIL-101(Cr)-SO3H], featuring varied ratios of Lewis acid site to Br?nsted acid site, were synthesized by hydrothermal reaction method starting from Cr(NO3)3·9H2O and sodium 2-sulfoterephthalate under various conditions of temperature and reaction time. The catalysts were characterized by techniques of PXRD, EDX, SEM, ICP-AAS and BET surface area, and the catalytic performances for glucose conversion to 5-HMF were evaluated. It showed that, in terms of the catalysis kinetics, Cr3+ serves as the Lewis acid sites of MIL-101(Cr)-SO3H for glucose isomerization, and sulfonic acid group, the Br?nsted acid site for the fructose dehydration. The highest HMF selectivity of 47.15% and the highest HMF yield of 46.0% was achieved under conditions of molar ratio of Br?nsted acid site to Lewis acid site of 1.1, 150℃ for 2 h.

Glucose conversion to 5‐hydroxymethylfurfural (HMF) generally undergoes catalytic isomerization reaction by Lewis acids followed by the catalytical dehydration to HMF with Brönsted acid. In this work, a sulfonic acid functionalized metal‐organic framework MIL‐101(Cr)‐SO 3 H containing both Lewis acid and Brönsted acid sites, was examined as the catalyst for γ‐valerolactone‐mediated cascade reaction of glucose dehydration into HMF. Under the optimal reaction conditions, the batch heterogeneous reaction gave a HMF yield of 44.9% and selectivity of 45.8%. Reaction kinetics suggested that the glucose isomerization in GVL with 10 wt % water follows the second‐order kinetics with an apparent activation energy of 100.9 kJ mol −1 . Continuous reaction in the fixed‐bed reactor showed that the catalyst is highly stable and able to provide a steady HMF yield. This work presents a sustainable and green process for catalytic dehydration of biomass‐derived carbohydrate to HMF with a bifunctional metal‐organic framework. © 2016 American Institute of Chemical Engineers AIChE J , 62: 4403–4417, 2016

Introduction of Ag(i) ions into a sulfonic acid functionalized MOF ((Cr)-MIL-101-SO3H) significantly enhances its interactions with olefin double bonds, leading to its much higher selectivities for the separation of C2H4-C2H6 and C3H6-C3H8 at room temperature over the original (Cr)-MIL-101-SO3H and other adsorbents at room temperature.

A metal-organic framework immobilized with Ag(i) sites, namely, (Cr)-MIL-101-SO3Ag, was successfully developed as a highly efficient desulfurization adsorbent because of the strong binding of these Ag(i) sites for thiophene derivatives.