We herein report the fabrication of a palladium nanoparticles (Pd NPs) loaded homochiral covalent organic framework using S-(+)-2-methylpiperazine and cyanuric chloride (Pd@CCOF-MPC) (2) via a very facile chemical approach. The chiral COF support of 1 (CCOF-MPC) is synthesized by the combination of cyanuric chloride and S-(+)-2-methylpiperazine at 90 °C for 36 h, and the Pd NPsloaded Pd@CCOF-MPC ( 2) is prepared via sequential solution impregnation and NaBH 4 reduction at room temperature. 2, as a highly active reusable asymmetric heterogeneous composite catalyst, is able to effectively promote the Henry reaction and reductive Heck reaction in high yield with excellent stereoselectivity.
A robust Zr-MOF (LIFM-28) containing replaceable coordination sites for additional spacer installation has been employed to demonstrate a swing- or multirole strategy for multifunctional MOFs. Through reversible installation/uninstallation of two types of spacers with different lengths and variable functional groups, different tasks can be accomplished using the same parent MOF. An orthogonal optimizing method is applied with seven shorter (L) and six longer (L) spacers to tune the functionalities, achieving multipurpose switches among gas separation, catalysis, click reaction, luminescence, and particularly, ultrahigh methane storage working capacity at 5-80 bar and 298 K.
To combine flexibility and modifiability towards a more controllable complexity of MOFs, a post-synthetic variable-spacer installation (PVSI) strategy is used to implement kinetic installation/ uninstallation of secondary ligands into/from a robust yet flexible proto-Zr-MOF. This PVSI process features precise positioning of spacers with different length, size, number, and functionality, enabling accurate fixation of successive breathing stages and fine-tuning of pore surface. It shows unprecedented synthetic tailorability to create complicated MOFs in a predictable way for property modification, for example, CO2 and R22 adsorption/separation, thermal/chemical stability, and extended breathing behavior.
We demonstrate herein a facile strategy
to engineer versatile catalytically
active coordination interspace in the same primitive metal–organic
framework (MOF) for variable heterogeneous catalysis. Different functional
ligands can be reversibly inserted into and removed from proto-LIFM-28 individually or successively to bring in single or binary
catalytic sites for specific reactions and switch the parent MOF to
multipurpose catalysts. Alcohol-oxidation, Knoevenagel-condensation,
click, acetal, and Baylis–Hillman reactions are achievable
through simple exchange of a single catalytic spacer, while sequential
or stepwise reactions are designable via selective combination of
two catalytic spacers with different functionalities, thus making proto-LIFM-28 a multivariate MOF for multiuse and economic
catalysis.
Herein, a dynamic spacer installation (DSI) strategy has been implemented to construct a series of multifunctional metal—organic frameworks (MOFs), LIFM‐61/31/62/63, with optimized pore space and pore environment for ethane/ethylene separation. In this respect, a series of linear dicarboxylic acids were deliberately installed in the prototype MOF, LIFM‐28, leading to a dramatically increased pore volume (from 0.41 to 0.82 cm3 g−1) and reduced pore size (from 11.1×11.1 Å2 to 5.6×5.6 Å2). The increased pore volume endows the multifunctional MOFs with much higher ethane adsorption capacity, especially for LIFM‐63 (4.8 mmol g−1), representing nearly three times as much ethane as the prototypical counterpart (1.7 mmol g−1) at 273 K and 1 bar. Meanwhile, the reduced pore size imparts enhanced ethane/ethylene selectivity of the multifunctional MOFs. Theoretical calculations and dynamic breakthrough experiments confirm that the DSI is a promising approach for the rational design of multifunctional MOFs for this challenging task.
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