Smoothing the single-crystal to single-crystal conversions of a two-dimensional metal–organic framework via the hetero-metal doping of the linear trimetallic secondary building unit

Abstract

The two-dimensional (2D) metal–organic framework (MOF) [Cd_2.25Co_0.75(BTB)₂(DEF)₄]·2(DEF)_0.5 (1a, BTB = benzene-1,3,5-tribenzolate; DEF = N,N′-diethylformamide) featuring linear trimetallic cluster secondary building units (SBUs) and replaceable DEF solvates reacts smoothly with dipyridyl ligands DPS, DPDS, and BIPY (DPS = 4,4′-dipyridyl sulfide; DPDS = 4,4′-dipyridyl disulfide; BIPY = 4,4′-bipyridine), yielding three-dimensional (3D) non-interpenetrated [Cd_2.25Co_0.75(BTB)₂(DPS)₂]·xSol (2) and [Cd_2.25Co_0.75(BTB)₂(DPDS)₂]·xSol (3), and interpenetrated [Cd_2.25Co_0.75(BTB)₂(BIPY)(H₂O)₂]·xSol (4). The smooth conversion of 1a to 3 contrasts the drastic single-crystal to single-crystal (SCSC) conversion observed for the homometallic [Cd₃(BTB)₂(DEF)₄]·2(DEF)_0.5 (1b), presumably due to the presence of the relatively Lewis acidic Co²⁺ that lessens the propensity for binding by soft dipyridyl donors. Activated samples of 2–4 showed no obvious absorption of N₂ at 77 K, but reversible type I uptake of CO₂ at 195 K.