Rational Design of a ZnII MOF with Multiple Functional Sites for Highly Efficient Fixation of CO2 under Mild Conditions: Combined Experimental and Theoretical Investigation.

The development of efficient heterogeneous catalysts suitable for carbon capture and utilization (CCU) under mild conditions is a promising step towards mitigating the growing concentration of CO2 in the atmosphere. Herein, we report the construction of a hydrogen-bonded 3D framework, {[Zn(hfipbba)(MA)]⋅3 DMF}n (hfipbba=4,4'-(hexaflouroisopropylene)bis(benzoic acid)) (HbMOF1) utilizing ZnII center, a partially fluorinated, long-chain dicarboxylate ligand (hfipbba), and an amine-rich melamine (MA) co-ligand. Interestingly, the framework possesses two types of 1D channels decorated with CO2 -philic (-NH2 and -CF3 ) groups that promote the highly selective CO2 adsorption by the framework, which was supported by computational simulations. Further, the synergistic involvement of both Lewis acidic and basic sites exposed in the confined 1D channels along with high thermal and chemical stability rendered HbMOF1 a good heterogeneous catalyst for the highly efficient fixation of CO2 in a reaction with terminal/internal epoxides at mild conditions (RT and 1 bar CO2 ). Moreover, in-depth theoretical studies were carried out using periodic DFT to obtain the relative energies for each stage involved in the catalytic reaction and an insight mechanistic details of the reaction is presented. Overall, this work represents a rare demonstration of rational design of a porous ZnII MOF incorporating multiple functional sites suitable for highly efficient fixation of CO2 with terminal/internal epoxides at mild conditions supported by comprehensive theoretical studies.

Rational Design of a 3D MnII -Metal-Organic Framework Based on a Nonmetallated Porphyrin Linker for Selective Capture of CO2 and One-Pot Synthesis of Styrene Carbonates.

A 3D MnII -porphyrin metal-organic framework (MOF), [{Mn2 (TCPP)⋅2H2 O}⋅DMF]n (MOF1) (TCPP=5,10,15,20-tetrakis(4-benzoate)porphyrin), was constructed; it exhibits an interesting 3D framework structure with two types of 1D channels of dimensions of 3.94×8.37 Å2 and 4.66×4.93 Å2 running along the crystallographic a axis. Owing to the presence of a nonmetallated porphyrin cavity, MOF1 exhibits selective storage of CO2 with an isosteric heat of adsorption value of 32.1 kJ mol-1 , which is further supported by theoretical calculations with the calculated binding energy (BE) of 29.78 kJ mol-1 . Interestingly, the nonmetallated nature of the porphyrin ligand was exploited for implantation of coordinatively unsaturated FeIII ions to generate a FeIII @MOF1 framework, which acts as an efficient recyclable catalyst for the oxidation of styrenes to the corresponding epoxides in the presence of PhIO as an oxidant at room temperature. Moreover, the one-pot synthesis of styrene carbonates from styrenes and CO2 was also achieved using FeIII @MOF1 as a catalyst. The rational design of a porous MnII -porphyrin MOF for the selective capture of CO2 and the one-pot synthesis of styrene carbonates at mild conditions is reported.