pubs.acs.org/JACS Article Multicomponent, Functionalized HKUST‑1 Analogues Assembled via Reticulation of Prefabricated Metal−Organic Polyhedral Cavities Akim Khobotov-Bakishev, Cornelia von Baeckmann, Borja Ortín-Rubio, Laura Hernández-López, Alba Cortés-Martínez, Jordi Martínez-Esaín, Felipe Gándara, Judith Juanhuix, Ana E. Platero-Prats, Jordi Faraudo, Arnau Carné-Sánchez,* and Daniel Maspoch* Cite This: J. Am. Chem. Soc. 2022, 144, 15745−15753 Read Online ACCESS Metrics & More Article Recommendations * sı Supporting Information ABSTRACT: Metal−organic frameworks (MOFs) assembled from multiple building blocks exhibit greater chemical complexity and superior functionality in practical applications. Herein, we report a new approach based on using prefabricated cavities to design isoreticular multicomponent MOFs from a known parent MOF. We demonstrate this concept with the formation of multicomponent HKUST-1 analogues, using a prefabricated cavity that comprises a cuboctahedral Rh(II) metal−organic polyhedron functionalized with 24 carboxylic acid groups. The cavities are reticulated in three dimensions via Cu(II)-paddlewheel clusters and (functionalized) 1,3,5-benzenetricarboxylate linkers to form three- and four-compo- nent HKUST-1 analogues. ■ INTRODUCTION The combination of multiple organic linkers and metal ions level, MOFs can also be seen as the product of connecting higher order structures18,19 such as different cavities or metal− into multicomponent or multivariate metal−organic frame- organic polyhedral (MOP)20 units, whether directly or through additional, small MBBs.21,22 Herein, we propose using MOPs works (MOFs) is a fruitful strategy to achieve greater chemical as prefabricated cavities from which a parent MOF structure complexity in MOFs, expand the catalogue of MOFs accessible can be replicated, whereby its composition is changed. by synthesis, and optimize the use of MOFs for applications Our strategy begins with a de-reticulation exercise in which a such as gas storage,1 water harvesting,2 and catalysis.3 In these repetitive cavity of the parent MOF is identified. Following the MOFs, complexity derives from the random or periodic example of HKUST-1, this enabled us to identify a repetitive arrangement of multiple organic and metallic functionalities cavity that defines a 24-c cuboctahedral MOP. Thus, we into the same structure.4 To date, strategies to design reasoned that the formation of the HKUST-1 structure would multicomponent or multivariate MOFs include bottom-up require the connection of these MOPs through the original 4-c synthesis by using any of the following: distinct linkers that Cu(II)-paddlewheel cluster and the 3-c btc. This leads to a have identical backbones but differ in their respective side change in the structural description of HKUST-1, from a groups or isostructural clusters comprising different metal ions, binary 3,4-c structure that comprises one inorganic (Cu(II)- to produce multivariate MOFs;5,6 or structurally different paddlewheel cluster) and one organic (btc) MBB to a tertiary linkers or metal clusters, to generate ordered multicomponent 3,4,24-c structure that comprises these two MBBs and the 24-c MOFs.7−10 Alternatively, the complexity of parent MOF MOP. We anticipated that this would enable use of three structures can be augmented through post-synthetic mod- components in the synthesis of HKUST-1 that, if distinct, ification via covalent and coordination chemistry,11,12 ligand would occupy specific positions in the replicated structure, installation,13 and linker- or metal-exchange.14 thereby generating ordered multicomponent MOFs isoreticu- Herein we propose a new approach to isoreticular, lar to HKUST-1. The basis of our approach is also supported multicomponent MOFs by starting with a known MOF. Reticular chemistry enables the rational synthesis of MOFs through the connection of basic molecular building blocks Received: June 12, 2022 (MBBs).15,16 For example, the archetypical HKUST-1 is Published: August 16, 2022 typically described as a 3,4-connected (3,4-c) network with an underlying tbo topology that is assembled from two MBBs: the 4-c Cu(II)-paddlewheel cluster and the 3-c 1,3,5- benzenetricarboxylate (btc) linker.17 However, on a conceptual © 2022 The Authors. Published by American Chemical Society https://doi.org/10.1021/jacs.2c06131 15745 J. Am. Chem. Soc. 2022, 144, 15745−15753 Journal of the American Chemical Society pubs.acs.org/JACS Article Figure 1. Schematic of the synthesis of three- and four-component HKUST-1 analogues using our design approach to multicomponent MOFs, based on the identification and exploitation of prefabricated cavities in the corresponding parent MOF. by the supermolecular building block approach described by addition of the three MBBs: COOH-RhMOP, the Cu(II)- Eddaoudi et al., in which an in situ-synthesized23,24 or pre- paddlewheel cluster, and btc. To determine this stoichiometry, assembled25 MOP is used as a highly connected node encoded we studied the connectivity of the three MBBs in the targeted with specific geometric and connectivity information to reduce structure (Figure 2). To mimic this structure, each COOH- the degrees of freedom of the network’s constituents and direct RhMOP must be connected to six neighboring COOH- their assembly toward a target highly connected structure. RhMOPs through 24 Cu(II)-paddlewheel clusters. In this However, herein, we use MOPs in a different way. In the connectivity, each COOH-RhMOP is bridged to a neighboring prefabricated directed synthesis, the MOP does not behave as COOH-RhMOP via four Cu(II)-paddlewheel clusters (Figure an in situ-formed node in a network, but rather as a preformed 2, yellow inset). Each Cu(II)-paddlewheel cluster must then be tiling of the targeted network, one which dictates the connected to four other Cu(II) clusters, via coordination of arrangement of the metallic and organic MBBs around it to two btc linkers to their two remaining adjacent positions ultimately generate a structure that is not necessarily described (Figure 2, violet inset). Overall, this connectivity defines a as highly connected (in this case, HKUST-1). Thus, the work Cu(II)-cluster/btc/COOH-RhMOP ratio of 12:8:1. This that we present here expands the utility of MOPs in MOF connectivity also defines the relative position of each metal chemistry, thereby providing a new route to complex ion within the HKUST-1 network. Thus, RhCu-btc-HKUST-1 multicomponent networks. would present two types of cuboctahedral cavities in its structure: the Rh(II)-based cavity that derives from the ■ RESULTS AND DISCUSSION Prefabricated Cavity-Directed Synthesis of Multi- prefabricated cavity, and a mixed-metal cavity containing Cu(II) and Rh(II) ions generated upon the self-assembly reaction. These cavities alternate throughout the structure metallic HKUST-1. We first applied our prefabricated cavity (Figure S1). This degree of control over the relative position of approach to HKUST-1 (Figure 1), choosing our previously cavities that contain different functionalities within porous reported Rh(II) cuboctahedral MOP functionalized with 24 frameworks has only been demonstrated for mixed-cage porous carboxylic acid groups (hereafter named COOH-RhMOP) as solids, in which different MOPs are co-precipitated.28−30 the prefabricated cavity.25,26 We selected COOH-RhMOP We began the synthesis of RhCu-btc-HKUST-1, whose because of its high chemical stability27 and its structural formula is [COOH-RhMOP(Cu)24(btc)8], by heating a difference relative to its Cu(II) analogue, which would lead to mixture of COOH-RhMOP with 24 mol equiv of Cu- pure HKUST-1. Using this MOP as a prefabricated cavity (NO3)2·3H2O and 8 mol equiv of btc in N,N-dimethylforma- enabled us to replicate the structure of HKUST-1, thereby mide (DMF) at 85 °C for 1 day. The solvothermal reaction forming the isoreticular three-component RhCu-btc-HKUST-1 yielded a colloidal green dispersion. A green crystalline solid comprising COOH-RhMOPs, Cu(II)-paddlewheel clusters, (yield: 78%; Figure 3a) was then isolated through and btc. centrifugation, washed with DMF, methanol, water, and Using COOH-RhMOP as a prefabricated cavity in the acetone, and then dried at room temperature. Field emission synthesis of RhCu-btc-HKUST-1 requires the stoichiometric scanning electron microscopy (FESEM) analysis of the green 15746 https://doi.org/10.1021/jacs.2c06131 J. Am. Chem. Soc. 2022, 144, 15745−15753 Journal of the American Chemical Society pubs.acs.org/JACS Article Figure 3. (a) Photographs of as-made (left) and activated (right) RhCu-btc-HKUST-1 powder. Scale bar: 1 cm. (b) Rietveld analysis of RhCu-btc-HKUST-1. (c) N2-sorption isotherms for RhCu-btc- HKUST-1. plasma-mass spectrometry (ICP-MS) measurements per- formed in acid-digested samples revealed that the Cu/Rh ratio was 1.02 ± 0.02, in agreement with the expected ratio in RhCu-btc-HKUST-1. Synchrotron powder X-ray diffraction (PXRD) data collected on RhCu-btc-HKUST-1 revealed a pattern nearly coincidental with that of the parent Cu(II)-based HKUST-1 (Figure S5), with only slight shifts in the position of the peaks attributable to small differences in lattice parameters. Starting with the reported HKUST-1 atomic positions in the cubic Fmm3̅m space group, a satisfactory Rietveld refinement was reached (Rp = 3.32%, Rwp = 4.68%), corresponding to a Figure 2. Schematic of the connectivity of COOH-RhMOPs (dark structure in which Rh(II) and Cu(II) atoms each occupy 50% gray cages), Cu(II)-paddlewheel clusters (blue squares), and btc of the crystallographic metal site in the paddlewheel clusters linkers (red triangles) to form RhCu-btc-HKUST-1. The inset details (Figure 3b and Table S1). This refinement demonstrated that the connectivity between two COOH-RhMOPs. RhCu-btc-HKUST-1 is isoreticular to HKUST-1, having the same network type. While the metal atoms in RhCu-btc- solid revealed the formation of a uniform sample comprising HKUST-1 are located at topologically and symmetrically particles having an average size of 22 ± 3 nm (Figure S2). equivalent positions, their framework distribution in the MBBs Energy-dispersive X-ray spectroscopy performed on these is directed by using COOH-RhMOP. In addition, pair single particles using high-resolution transmission electron distribution function analyses of synchrotron X-ray scattering microscopy corroborated the presence of both Rh and Cu in data showed the uniquely occurrence of Cu···Cu and Rh···Rh each tested particle (Figure S3). Moreover, the oxidation states distances, thereby demonstrating the lack of hetero-bimetallic of both Rh and Cu were found to be +2 through X-ray paddlewheel clusters in RhCu-btc-HKUST-1 (Figures S6 and photoelectron spectroscopy (Figure S4). Inductively coupled S7). 15747 https://doi.org/10.1021/jacs.2c06131 J. Am. Chem. Soc. 2022, 144, 15745−15753 Journal of the American Chemical Society pubs.acs.org/JACS Article To further confirm the MOP-guided assembly of RhCu-btc- that the RhCu-btc-HKUST-1 had retained its crystallinity HKUST-1, we ran a series of control experiments (see the (Figure S21). Supporting Information (SI)). Initially, we corroborated the Hydrolytic Stability of RhCu-btc-HKUST-1. We rea- stability of COOH-RhMOP under the reaction conditions soned that the presence of the water-stable COOH-RhMOP (DMF, 85 °C, 1 day) by 1H NMR, UV−vis, and mass cavity within RhCu-btc-HKUST-1 could confer the overall spectrometry (Figures S9−S11). Then, we ran three blank structure with greater hydrolytic stability relative to the parent reactions under the above conditions but lacking one of the Cu(II)-HKUST-1. To test this hypothesis, we incubated three MBBs. As expected, we did not observe the formation of RhCu-btc-HKUST-1 and the parent Cu(II)-HKUST-1 in RhCu-btc-HKUST-1 in any of those reactions. Specifically, the liquid water at room temperature from 1 to 31 days. The reaction of Cu(II) and btc yielded microcrystals of the water-incubated samples were then characterized through expected parent, Cu(II)-HKUST-1. The reaction of COOH- FESEM, PXRD, and N2 sorption. To our surprise, RhCu- RhMOP with btc produced a clear green solution without any btc-HKUST-1 had retained its morphology, crystallinity, precipitate. This result further confirms that there is no composition, and porosity, even after 1 month of incubation leaching of Rh(II) ions from COOH-RhMOP; as these in liquid water (Figure 4a,b, Figures S23 and S30−S35). eventual leached Rh(II) ions would react with btc to yield Conversely, upon exposure to water, the parent Cu(II)- an extended coordination polymer.26 Finally, the reaction of HKUST-1 had undergone the well-reported phase change, COOH-RhMOP with Cu(II) yielded an amorphous coordi- with a corresponding loss of porosity from 1888 to 502 m2/g nation polymer. Additionally, we reacted preformed Cu(II)- within the first day (Figures S24−S29).32 HKUST-1 crystals with COOH-RhMOP in a mixture The hydrolytic stability that we observed for RhCu-btc- containing the same molar ratio of Cu(II)-cluster/btc/ HKUST-1 implies that not only the COOH-RhMOP cavities, COOH-RhMOP as that (12:8:1) used for the synthesis of RhCu-btc-HKUST-1. Under these conditions, we did not observe the formation of RhCu-btc-HKUST-1 crystals (Figure S12). This experiment demonstrates that the reaction mechanism cannot proceed through an initial formation of Cu(II)-HKUST-1 crystals that evolve through solubilization− recrystallization toward the formation of RhCu-btc-HKUST-1. We reasoned that, conversely, the most plausible scenario is that the presence of the COOH-RhMOP rapidly nucleates the formation of RhCu-btc-HKUST-1, thereby suppressing the formation of Cu(II)-HKUST-1. We confirmed the presence of COOH-RhMOP cavities and btc linkers within the structure of RhCu-btc-HKUST-1 through solid-state cross-polarized/magic angle spinning (CP/MAS) 13C NMR (Figure S13). To quantify the molar ratio between the prefab cavities and the added btc linkers, we developed a methodology to revert the assembly process into its initial components, which we identified and then quantified (Figures S14−S17). This was based on the high chemical stability of COOH-RhMOP. Upon exposing a DMF dispersion of RhCu-btc-HKUST-1 crystals to acidic conditions (see SI), we found that they become fully redissolved. 1H NMR (DMF- d7) of the resulting solution revealed a btc/COOH-RhMOP ratio of 8:1, in agreement with the ratio expected in RhCu-btc- HKUST-1 (Figure S16). We were able to quantify the amount of liberated COOH-RhMOP by UV−vis spectroscopy. From this experiment, we calculated a concentration of 93.3 μmol COOH-RhMOP/g of RhCu-btc-HKUST-1, which is very close to the theoretical value (94.2) (Figure S17 and Table S2). Altogether, our results confirmed the formation of RhCu- btc-HKUST-1 without significant defects and that COOH- RhMOP remains intact during its synthesis. Next, we performed N2-sorption measurements on activated RhCu-btc-HKUST-1 at 77 K, finding that it is microporous to N2, with a BET surface area (SBET) of 1606 m2/g (Figure 3c, Figure 4. (a) PXRD diffractogram and (b) N2-sorption isotherms for Figure S18). Furthermore, pore-size distribution analysis RhCu-btc-HKUST-1 initially (green) and after incubation in water for revealed the presence of the three characteristic cavities of 3 (red), 14 (orange), and 31 days (blue). Snapshots (orthographic views) of the optimized DFT structures of (c) Cu(II)- and (d) the HKUST-1 structure together with some mesoporosity, Rh(II)-paddlewheel clusters in water. (e) CO2-sorption isotherms at which we ascribed to the interparticle voids (Figure S20). This 298 K for RhCu-btc-HKUST-1 initially (green) and after incubation extrinsic porosity is also responsible for the increased uptake at in water for 3 days (red), 14 days (orange), and 31 days (blue). (f) high pressure (P/P0 ≈ 0.6) and the observed hysteresis loop, as Removal of MB in water by RhCu-btc-HKUST-1 as a function of previously observed for other nanoscopic MOFs.31 PXRD time. Inset: five consecutive MB-removal/regeneration cycles using diffractogram recorded after these sorption studies confirmed RhCu-btc-HKUST-1. 15748 https://doi.org/10.1021/jacs.2c06131 J. Am. Chem. Soc. 2022, 144, 15745−15753 Journal of the American Chemical Society pubs.acs.org/JACS Article Figure 5. (a) Schematic of the four-component HKUST-1 analogues, showing the three types of channels that are generated when the COOH- RhMOP (structure depicted in gray and cavity depicted in green) is co-assembled with Cu(II) paddlewheels (blue) and (functionalized) btc linkers (orange). (b) Highlight of the chemical structure of the 1D channel decorated exclusively with functionalized btc linkers. (c) Highlight of the coordination environment of the (COOH)btc linker within the channels of RhCu-(COOH)btc-HKUST-1. (d) PXRD diffractogram of RhCu- (NH2)btc-HKUST-1 (blue), RhCu-(NO2)btc-HKUST-1 (orange), RhCu-(Br)btc-HKUST-1 (purple), and RhCu-(COOH)btc-HKUST-1 (red). (e) CO2-adsorption isotherms at 298 K for RhCu-(NH2)btc-HKUST-1 (blue), RhCu-(NO2)btc-HKUST-1 (orange), RhCu-(Br)btc-HKUST-1 (purple), and RhCu-(COOH)btc-HKUST-1 (red). but also the Cu(II)-carboxylate bonds that link them, the CO2 adsorption capacity of RhCu-btc-HKUST-1 after withstand the incubation in water. Thus, in an effort to being incubated in water for up to 31 days. As observed in rationalize the higher hydrolytic stability of RhCu-btc- Figure 4e, CO2 uptake capacity did not decrease after the HKUST-1, we performed electronic structure calculations in incubation. Additionally, we tested the adsorption capabilities water of both Cu(II)- and Rh(II)-paddlewheel clusters (Figure of RhCu-btc-HKUST-1 in liquid water. To this end, we 4c,d). For this, we employed Gaussian 1633 at the M06-L/ incubated RhCu-btc-HKUST-1 in an aqueous solution of SDD level of theory34 in the presence of implicit water solvent methylene blue (MB) at 20 ppm (pH = 7) and then monitored modeled with the IEFPCM formalism, as described in the SI.35 the decrease of MB over 1 h. We found that, after 51 min, 97% Our implicit solvent calculations showed that the Cu(II)- of the MB had been removed by the RhCu-btc-HKUST-1 paddlewheel undergoes a significant torsion when exposed to (Figure 4f). Moreover, after the MB-adsorption, the RhCu-btc- water, whereas the Rh(II)-paddlewheel remains stable (Figures HKUST-1 fully retained its crystallinity (Figure S44). This S36−S38). This torsion is enhanced after coordination of a contrasts sharply to the case of its parent, Cu(II)-HKUST-1, water molecule to the axial position of Cu(II) (Figure 4c, which, in the same amount of time, could adsorb 62% of the Figures S39−S41), disrupting the original symmetrical MB, due to its degradation and amorphization in water bidentate binding with carboxylate ligands (Figure S42). We (Figures S43 and S45). To explore the MB-removal perform- propose that Cu(II)-paddlewheels are hydrolyzed through this ance of each analogue after reutilization, we tested them over mechanical distortion as pivotal step, provoking the instability five consecutive removal/regeneration cycles. The removal of the parent Cu(II)-HKUST-1. In the case of RhCu-btc- step was identical to the one followed above. The regeneration HKUST-1, each Cu(II)-paddlewheel is connected to two step entailed the recovery of the adsorbent through Rh(II)-paddlewheel clusters, which are not altered by water. centrifugation, followed by successive washings with water The inertness of the Rh(II)-paddlewheel blocks the mechan- and acetone. Finally, the adsorbent was activated at 85 °C ical instability of the neighboring Cu(II)-paddlewheel, thereby under vacuum for 1 h. The results showed that uptakes of inhibiting the hydrolysis process. RhCu-btc-HKUST-1 were similar among the five cycles We envisioned that the stability of RhCu-btc-HKUST-1 (Figure 4f, inset), meaning that it had remained stable and could enable its use as an adsorbent in aqueous environments that the regeneration was sufficient to maintain its removal or after aqueous exposure. As a proof of concept, we evaluated capacity. Contrariwise, under these conditions, the MB- 15749 https://doi.org/10.1021/jacs.2c06131 J. Am. Chem. Soc. 2022, 144, 15745−15753 Journal of the American Chemical Society pubs.acs.org/JACS Article removal capacity of Cu(II)-HKUST-1 dropped from 62% to in N2-sorption experiments, finding SBET values of 1215, 1133, ∼10% (from the second to third cycles), and then to ∼3−4% and 1212 m2/g, respectively (Figures S49, S56, and S63). In all (for the fourth and fifth cycles) (Figure S43). Thus, the cases, PXRD diagrams collected after the sorption studies also difference in MB-removal performance between RhCu-btc- confirmed their stability (Figures S51, S58, and S65). All these HKUST-1 and Cu(II)-HKUST-1 only widened after reutiliza- SBET values are lower than the SBET value for RhCu-btc- tion, suggesting a new mechanism for stabilization of Cu(II) HKUST-1. We ascribed their inferior porosity to steric paddlewheel clusters based on the mechanical interlock hindrance of the side groups located within the pores�a between Rh(II) and Cu(II) paddlewheels, which results in feature common to many other MOFs, such as those of the water-resistant adsorbents. UiO-66 family.37 Whereas N2-sorption isotherms at 77 K Reticulation of Varied Linkers into the HKUST-1 accounted for the steric hindrance of the functional groups Structure via Prefabricated Cavity-Directed Synthesis. introduced into these four-component HKUST-1 analogues, We envisaged that our prefabricated cavity strategy would CO2-adsorption measured at 298 K highlighted their different provide access to four-component HKUST-1 analogues, given affinities toward CO2. Thus, the presence of free amine groups the possibility to differentiate the btc linkers that form the in RhCu-(NH2)btc-HKUST-1 made it a better adsorbent for COOH-RhMOP from those that bridge the Cu(II)-paddle- CO2 than its Br or NO2 analogues (Figure 5e). wheel clusters, during the synthesis. However, we reasoned COOH-Functionalized HKUST-1 Analogue. Having that such four-component analogues would require a function- observed the structure-directing properties of the COOH- alized btc linker, rather than the previously used btc linker. In RhMOP prefabricated cavity on the synthesis of multi- this new configuration, the connectivity of the prefabricated component HKUST-1 analogues, we envisaged that it could COOH-RhMOP cavity dictates that the added functionalized be employed to reticulate tetracarboxylate linkers to function- btc linkers will be located on top of the triangular windows that alize the HKUST-1 architecture with free carboxylic acid connect three Cu(II) paddlewheels. These positions align into groups. Thus, we employed 1,2,3,5-benzenetetracarboxylic acid 1D channels, thus generating four-component HKUST-1 (hereafter named (COOH)btc) as the organic MBB in the co- analogues in which alternating functionalized and non- assembly of COOH-RhMOP with Cu(II) paddlewheels to functionalized 1D channels coexist (Figure 5a). This scenario yield RhCu-(COOH)btc-HKUST-1 (Figure 5b,c). The differs from the outcome obtained when linkers with the same solvothermal reaction between COOH-RhMOP, Cu(NO3)2· connectivity but different side functionalities are combined to 3H2O, and (COOH)btc afforded a green crystalline sample generate isoreticular frameworks. In this latter case, one made of particles of an average size of 20 ± 3 nm (yield: 65%) generally obtains structures in which the different linkers are (Figure S67). PXRD analysis of RhCu-(COOH)btc-HKUST-1 randomly distributed or are organized into a non-atomically revealed a pattern consistent with RhCu-btc-HKUST-1 precise pattern.36 (Figure 5d). The successful reticulation of (COOH)btc within Based on the prefab cavity-induced desymmetrization of the the HKUST-1 network was confirmed by the 1H NMR organic linkers within the HKUST-1 network, we attempted spectrum of the acid-digested sample, which showed a btc/ the synthesis of four-component HKUST-1 analogues, using (COOH)btc ratio of 8:1 (Figure S69). The thermally activated btc linkers having a pendant functional group [(Br)btc, sample retained its crystallinity (Figure S72), which enabled (NO2)btc and (NH2)btc] at the second position of the measurement of its gas sorption, for which an SBET of 1380 m2/ phenylic ring as one of the reagents. Thus, we followed a g (Figure S70) and a CO2 uptake (at 298 K and 1 bar) of 4.0 synthetic strategy identical to the one that we had used for mmol/g were found (Figure 5e). RhCu-btc-HKUST-1, except that we substituted the non- To further confirm that RhCu-(COOH)btc-HKUST-1 functionalized btc linker with either (Br)btc, (NO2)btc or contained free carboxylic acid groups within its channels, we (NH2)btc to generate RhCu-(Br)btc-HKUST-1, RhCu- performed a series of spectroscopic characterizations. First, (NO2)btc-HKUST-1, and RhCu-(NH2)btc-HKUST-1, respec- ICP measurements performed on the acid-digested sample tively. The three reactions afforded green crystalline samples revealed that the Cu:Rh molar ratio was 0.94. The fact that composed of particles with an average size of 24 ± 2 nm, for there is no excess of Cu(II) ions in the HKUST-1 structure RhCu-(Br)btc-HKUST-1 (yield: 82%); 23 ± 2 nm, for RhCu- suggests that only three of the four COOH groups of the (NO2)btc-HKUST-1 (yield: 78%); and 21 ± 3 nm, for RhCu- (COOH)btc are coordinated to Cu(II) ions. Next, infrared (NH2)btc-HKUST-1 (yield: 74%) (Figures S46, S53, and spectroscopy performed on RhCu-(COOH)btc-HKUST-1 S60). showed a clear vibration band at 1702 cm−1, which we Next, we characterized RhCu-(Br)btc-HKUST-1, RhCu- ascribed to the stretching band of C�O, which indicates the (NO2)btc-HKUST-1, and RhCu-(NH2)btc-HKUST-1 by presence of uncoordinated carboxylic acid groups (Figure PXRD, finding that their patterns matched the one that we S73). Altogether, our results illustrate that our prefabricated- had previously obtained for RhCu-btc-HKUST-1 (Figure 5d). cavity approach can be employed to restrict the connectivity of ICP-MS on fully digested RhCu-(Br)btc-HKUST-1, RhCu- polycarboxylate linkers to introduce free carboxylic acid groups (NO2)btc-HKUST-1, and RhCu-(NH2)btc-HKUST-1 gave into multicomponent isoreticular structures. Accordingly, this Cu/Rh molar ratios of 1.16 ± 0.01, 1.10 ± 0.01, and 1.09 ± approach enabled the synthesis of a COOH-functionalized 0.02, respectively. These values are in good agreement with the HKUST-1 analogue without generation of any defective value (1) expected for their molecular formula. Moreover, 1H structures.38,39 NMR signals of the digested materials showed btc/(Br)btc, Finally, as a proof-of-concept, we aimed to demonstrate that btc/(NO2)btc, and btc/(NH2)btc ratios of 8:1, also in perfect the carboxylic acid groups located within the RhCu-(COOH)- agreement with the expected ratio according to their formula btc-HKUST-1 structure are functional and accessible. To this (Figures S48, S55, and S62). end, we evaluated the behavior of RhCu-(COOH)btc- We measured the porosity of RhCu-(Br)btc-HKUST-1, HKUST-1 as catalyst in a model acid-catalyzed reaction: the RhCu-(NO2)btc-HKUST-1, and RhCu-(NH2)btc-HKUST-1 conversion of benzaldehyde dimethyl acetal to benzalde- 15750 https://doi.org/10.1021/jacs.2c06131 J. Am. Chem. Soc. 2022, 144, 15745−15753 Journal of the American Chemical Society pubs.acs.org/JACS Article hyde.40,41 We observed that, under identical conditions, RhCu- Borja Ortín-Rubio − Catalan Institute of Nanoscience and (COOH)btc-HKUST-1 could convert up to 64% of Nanotechnology (ICN2), CSIC, Barcelona Institute of benzaldehyde dimethyl acetal into benzaldehyde, whereas Science and Technology, 08193 Bellaterra, Barcelona, Spain; non-functionalized RhCu-btc-HKUST-1 only afforded 32% Departament de Química, Facultat de Ciències, Universitat conversion (Figure S74). Considering that the acidic groups of Autònoma de Barcelona, 08193 Bellaterra, Spain; RhCu-btc-HKUST-1 can only be located at its surface, we orcid.org/0000-0002-0533-3635 ascribed the superior conversion obtained with RhCu- Laura Hernández-López − Catalan Institute of Nanoscience (COOH)btc-HKUST-1 to the activity of the inner carboxylic and Nanotechnology (ICN2), CSIC, Barcelona Institute of acid groups, which would confirm their accessibility. Science and Technology, 08193 Bellaterra, Barcelona, Spain; Importantly, both RhCu-btc-HKUST-1 and RhCu-(COOH)- Departament de Química, Facultat de Ciències, Universitat btc-HKUST-1 fully retained their crystallinity after the acid Autònoma de Barcelona, 08193 Bellaterra, Spain catalysis (Figure S75). Alba Cortés-Martínez − Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, Barcelona Institute of ■ CONCLUSIONS We have presented an alternative methodology to synthesize Science and Technology, 08193 Bellaterra, Barcelona, Spain; Departament de Química, Facultat de Ciències, Universitat multicomponent MOFs, which is based on the co-assembly of Autònoma de Barcelona, 08193 Bellaterra, Spain prefabricated cavities (in the form of carboxylic acid-function- Jordi Martínez-Esaín − Catalan Institute of Nanoscience and alized MOPs) and small MBBs. The methodology benefits Nanotechnology (ICN2), CSIC, Barcelona Institute of from the structure-directing influence of the MOP to organize Science and Technology, 08193 Bellaterra, Barcelona, Spain; varied organic and metallic MBBs through the crystal lattice of orcid.org/0000-0002-8420-8559 the targeted MOF, thus providing a greater degree of control Felipe Gándara − Consejo Superior de Investigaciones over the synthesis of atomically precise multicomponent Científicas (CSIC), Materials Science Institute of Madrid MOFs. (ICMM), 28049 Madrid, Spain; orcid.org/0000-0002- 1671-6260 ■ * ASSOCIATED CONTENT sı Supporting Information Judith Juanhuix − ALBA Synchrotron, 08290 Cerdanyola del Vallès, Barcelona, Spain; orcid.org/0000-0003-3728- 8215 The Supporting Information is available free of charge at Ana E. Platero-Prats − Departamento de Química Inorgánica, https://pubs.acs.org/doi/10.1021/jacs.2c06131. Facultad de Ciencias, Universidad Autónoma de Madrid, Detailed syntheses, FESEM data and images, PXRD 28049 Madrid, Spain; Condensed Matter Physics Center diffractogram, XPS, UV−vis, and NMR, as well as (IFIMAC), Universidad Autónoma de Madrid, 28049 porosity measurements, including Figures S1−S75 and Madrid, Spain; orcid.org/0000-0002-2248-2739 Tables S1−S3 (PDF) Jordi Faraudo − Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), 08193 Bellaterra, Spain; orcid.org/ 0000-0002-6315-4993 ■ AUTHOR INFORMATION Corresponding Authors Complete contact information is available at: https://pubs.acs.org/10.1021/jacs.2c06131 Arnau Carné-Sánchez − Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, Barcelona Institute of Notes Science and Technology, 08193 Bellaterra, Barcelona, Spain; The authors declare no competing financial interest. Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; orcid.org/0000-0002-8569-6208; Email: arnau.carne@ icn2.cat ■ ACKNOWLEDGMENTS This work was supported by the Spanish MINECO (project Daniel Maspoch − Catalan Institute of Nanoscience and RTI2018-095622-B-I00), the Catalan AGAUR (project 2017 Nanotechnology (ICN2), CSIC, Barcelona Institute of SGR 238), the CERCA Program/Generalitat de Catalunya, Science and Technology, 08193 Bellaterra, Barcelona, Spain; and the MCIN/AEI/10.13039/501100011033 and by the Departament de Química, Facultat de Ciències, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; ICREA, European Union “NextGenerationEU”/PRTR (EUR2020- 08010 Barcelona, Spain; orcid.org/0000-0003-1325- 112294). We also thank CESGA Supercomputing center for 9161; Email: daniel.maspoch@icn2.cat technical support and computer time at the supercomputer Finisterrae III. ICN2 and ICMAB are supported by the Severo Authors Akim Khobotov-Bakishev − Catalan Institute of Nanoscience Ochoa program from the Spanish MINECO (grants SEV- and Nanotechnology (ICN2), CSIC, Barcelona Institute of 2017-0706 and CEX2019-000917-S). The project that gave Science and Technology, 08193 Bellaterra, Barcelona, Spain; rise to these results received the support of a fellowship (LCF/ Departament de Química, Facultat de Ciències, Universitat BQ/PR20/11770011) from “la Caixa” Foundation (ID Autònoma de Barcelona, 08193 Bellaterra, Spain 100010434). A.E.P.-P. acknowledges a Ramón y Cajal Cornelia von Baeckmann − Catalan Institute of Nanoscience fellowship (RYC2018-024328-I). We acknowledge the Dia- and Nanotechnology (ICN2), CSIC, Barcelona Institute of Science and Technology, 08193 Bellaterra, Barcelona, Spain; mond Light Source, U.K., for the provision of synchrotron Departament de Química, Facultat de Ciències, Universitat access to the beamline I15-1 (CY28079) and thank Dr. Philip Autònoma de Barcelona, 08193 Bellaterra, Spain Chater for his assistance with data collection. 15751 https://doi.org/10.1021/jacs.2c06131 J. Am. Chem. Soc. 2022, 144, 15745−15753 Journal of the American Chemical Society pubs.acs.org/JACS Article ■ REFERENCES (1) Jiang, J.; Furukawa, H.; Zhang, Y.-B.; Yaghi, O. M. High (19) Belmabkhout, Y.; Mouttaki, H.; Eubank, J. F.; Guillerm, V.; Eddaoudi, M. Effect of Pendant Isophthalic Acid Moieties on the Adsorption Properties of Light Hydrocarbons in HKUST-1-like Tbo- Methane Storage Working Capacity in Metal-Organic Frameworks MOFs: Application to Methane Purification and Storage. RSC Adv. with Acrylate Links. J. Am. Chem. 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