Multi-descriptors guided constructing the microenvironment of frustrated Lewis pair bi-active sites in functionalized MOFs toward Sabatier optimal for catalytic hydrogenation

Precise design and regulation of active site accessibility and chemical properties within metal–organic frameworks (MOFs) are crucial for enhancing catalytic performance, yet pose significant challenges. This study presents a design strategy for functionalized MOF-808 catalysts featuring frustrated Lewis pair (FLP) bi-active sites for catalytic hydrogenation. More specifically, we modulated the microenvironment of Lewis acid-base sites (LA-LB) by 4 categories of monocarboxylic acid ligands (i.e., the 6-substituted BR₂ piperidine-2-carboxylic acid (FLP1-R), 1-substituted BR₂ pyrazole-2-carboxylic acid (FLP2-R), 5-substituted BR₂ pyrrolidine-2-carboxylic acid (FLP3-R) and 6-substituted BR₂ pyridine-2-carboxylic acid (FLP4-R)) exchange, in which the LA coordinated the substituent group (−R) is −H, –OH, –NH₂, –CH₃, −Br, −Cl, −F, –NO₂, −CF₃, or –CN. Utilizing density functional theory (DFT), it elucidates the electronic-level regulation mechanisms affecting catalytic performance. We establish screening principles for 40 functionalized MOFs, revealing linear relationships between the geometric and electronic structures of the active moiety (neutral FLP-R) and both adsorption energy and Gibbs free energy barriers. Multi-descriptors, the dihedral angle between LA, LB and the critical points (c₁ and c₂) of electron localization function (ELF) upon dual active sites (φ_c1-LB-LA-c2), the distance of LA and LB (D_LA&LB) and local chemical potential (μ_L) of FLP-R were firstly proposed to identify candidates favoring dissociative H₂ adsorption over chemisorbed dicyclopentadiene (DCPD), thereby mitigating bi-active site due to strongly bound. Furthermore, the intrinsic descriptor ${|\epsilon }_p^B|+|{\epsilon }_p^N|$ derived by the p band center of B atom (LA) and N atom (LB) yield an inverted volcano-shaped curve, with FLP3-CH₃, FLP4-F, FLP4-CH₃, and FLP4-OH functionalized MOF-808 positioned at the optimal point, balancing H₂ dissociation and the hydrogenation of 8,9-dihydrodicyclopentadiene (8,9-DHDCPD). Our work bridges the inherent characteristics of catalysts and their catalytic activities through the development of multi-descriptors, paving the way for high-performance MOF design.