Ci a ion: Echenique-E andonea, E.;
López-Va gas, M.E.; Pé ez, J.M.;
Rojas, S.; Choquesillo-Laza e, D.;
Seco, J.M.; Fe nández, I.;
Rod íguez-Diéguez, A. A Mixed
He e obime allic Y/Eu-MOF o he
Cyanosilyla ion and Hyd obo a ion
o Ca bonyls. Ca alys s 2022,12, 299.
h ps://doi.o g/10.3390/
ca al12030299
Academic Edi o : Jo ge Bedia
Recei ed: 10 Feb ua y 2022
Accep ed: 2 Ma ch 2022
Published: 6 Ma ch 2022
Publishe ’s No e: MDPI s ays neu al
wi h ega d o ju isdic ional claims in
published maps and ins i u ional a il-
ia ions.
Copy igh : © 2022 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license (h ps://
c ea i ecommons.o g/licenses/by/
4.0/).
ca alys s
A icle
A Mixed He e obime allic Y/Eu-MOF o he Cyanosilyla ion
and Hyd obo a ion o Ca bonyls
Es i xu Echenique-E andonea 1,† , Mi eya E. López-Va gas 2,†, Juana M. Pé ez 2, Sa a Rojas 3,
Duane Choquesillo-Laza e 4, JoséM. Seco 1, Ignacio Fe nández 2,* and An onio Rod íguez-Diéguez 3,*
1
Depa amen o de Química Aplicada, Uni e sidad del País Vasco UPV/EHU, Paseo Manuel La dizabal, N
◦
3,
20018 Donos ia-San Sebas ián, Spain; [email p o ec ed] (E.E.-E.); [email p o ec ed] (J.M.S.)
2Depa men o Chemis y and Physics, Resea ch Cen e CIAIMBITAL, Uni e si y o Alme ía,
Ca e e a Sac amen o s/n, 04120 Alme ía, Spain; mi [email p o ec ed] (M.E.L.-V.);
[email p o ec ed] (J.M.P.)
3
Depa amen o de Química Ino gánica, Facul ad de Ciencias, Uni e sidad de G anada, A . Fuen enue a s/n,
18071 G anada, Spain; s ojas@ug .es
4Labo a o io de Es udios C is alog á icos, IACT, CSIC-UGR, A . Las Palme as N◦4, A milla,
18100 G anada, Spain; [email p o ec ed]
*Co espondence: [email p o ec ed] (I.F.); an onio5@ug .es (A.R.-D.)
† These au ho s con ibu ed equally o his wo k.
Abs ac :
He ein, o he bes o ou knowledge, he i s he e obime allic Y/Eu po ous me al–o ganic
amewo k (MOF), based on 3-amino-4-hyd oxybenzoic acid (H
2
L) ligand, wi h he ollowing o -
mulae {[Y
3.5
Eu
1.5
L
6
(OH)
3
(H
2
O)
3
]
·
12DMF}
n
(in ad ance, namely
Y/Eu-MOF
), is desc ibed. The
h ee-dimensional s uc u e has been syn hesized by sol o he mal ou es and ho oughly cha ac e -
ized, by means o single c ys al X- ay di ac ion, powde X- ay di ac ion, elec onic mic oscopy,
ICP-AES, elec opho e ic mobili y, and FTIR spec a. In iguingly, he po ous na u e allows o coo -
dina ed sol en molecules displacemen , yielding unsa u a ed me al cen e s, which can ac as a Lewis
acid ca alys . This no el sup amolecula en i y has been es ed in cyanosilyla ion and hyd obo a ion
eac ions on ca bonyl subs a es o a di e se na u e, exhibi ing an ex ao dina y ac i i y.
Keywo ds:
he e obime allic; me al-o ganic amewo k; cyanosilyla ion; hyd obo a ion; y ium;
eu opium
1. In oduc ion
Me al-o ganic amewo ks a e mul i unc ional, ino ganic–o ganic sys ems composed
o o ganic ligands and me allic nodes and, since he 1990s, ha e eme ged as p omising
ma e ials o in ini e applica ions, among hem he e ogeneous ca alysis [1,2].
Thei in insic po osi y, along wi h easy unabili y and unc ionaliza ion, a e some o
he appealing cha ac e is ics o be employed in he e ogeneous ca alysis [
3
]. The s uc u al
po osi y p o ides a con ined space o which subs a es ha e access and ca alysis can ake
place. Fu he mo e, he MOF’s obus ness p o ides s able skele ons, whe e unsa u a ed
me allic cen e s can ac as a Lewis acid ca alys , subsequen displacemen o coo dina ed
sol en molecules could occu , and he u he ac i a ion o he subs a es al eady accessed
h ough he channels migh help he ca alysis e ol e [4].
In his con ex , cyanosilyla ion and hyd obo a ion eac ions ca alyzed by he e oge-
neous ca alys s, such as MOFs, a e p esen ed as in e es ing app oaches o he o ma ion
o cyanohyd ins and alcohols [5,6]. The cyanosilyla ion eac ion is an impo an syn he ic
ool o C–C bond o ma ion in o ganic sys ems, since i gi es access o key in e media es
o g ea in e es in he ield o pes icides and medical applica ion, among which
α
-hyd oxy
acids, α-hyd oxy ke ones, α-amino acids, and β-amino alcohols can be men ioned [7,8].
None heless, wi hin his ame o e e ence, he numbe o epo ed Ln-MOF ac ing
as a he e ogeneous ca alys in he cyanosilyla ion eac ion esul s we e ela i ely sca ce
Ca alys s 2022,12, 299. h ps://doi.o g/10.3390/ca al12030299 h ps://www.mdpi.com/jou nal/ca alys s
Ca alys s 2022,12, 299 2 o 10
(Table S10 summa izes he epo ed examples exhibi ing ac i i y, so a ) [
5
,
9
–
24
]. Mo eo e ,
o he bes o ou knowledge, lan hanide-based he e obime allic MOFs ha e ne e been
applied. In he ield o hyd obo a ion, he con ex is e en mo e unexplo ed. The syn hesis
o alcohols h ough his ou e has been explo ed ia MOF sys ems based on Ti, Fe, Co, and
Mg [
25
–
30
]; howe e , he e a e no p eceden s wi h hese sup amolecula en i ies buil on
lan hanides p ecu so s. The e o e, in his wo k, he i s example o y ium and eu opium-
based mixed MOF, wi h he o mula {[Y
3.5
Eu
1.5
L
6
(OH)
3
(H
2
O)
3
]
·
12DMF}
n
, is p esen ed,
aking he s ong backg ound o ou g oup in he examina ion o hese sup amolecula
sys ems in ca alysis [15,16].
The he e obime allic
Y/Eu-MOF
p esen ed he ein was designed when looking o a
syne gy and enhanced ca aly ic ac i i y, wi h espec o hei isos uc u al p is ine coun e -
pa s, which we e able o exhibi ac i i y o se en cycles, wi h e y low ca aly ic loading o
0.5 mol%, no ca alys leaking, TOF alues o 106 h
−1
and 1031 h
−1
, and p e e ed sui abili y
owa ds aldehydic and ke onic subs a es o Y-MOF [15] and Eu-MOF, espec i ely.
Taking all in o conside a ion, ou in e es lies in explo ing he ca aly ic ac i i y o his
no el he e obime allic MOF, based on 3-amino-4-hyd oxybenzoic acid poly opic ligand,
in he cyanosilyla ion and hyd obo a ion eac ions o aldehydes and ke ones o di e se
na u e unde sol en - ee and en i onmen ally iendly condi ions, in o de o e en ually
conclude whe he ca aly ic ac i i y enhances, wi h espec o ini ial coun e pa s.
2. Resul s and Discussion
2.1. P epa a ion o he Ca alys
The sol o he mal eac ion be ween 3-amino-4-hyd oxybenzoic acid (H
2
L) ligand and
Y-Eu me al mix u e in a basic media yields a h ee-dimensional, po ous, me al–o ganic
amewo k ha c ys allizes in hexagonal P63/mspace g oup. The asymme ic uni o
his sup amolecula en i y is composed o a dep o ona ed ligand molecule, wo me al
a oms wi h special posi ions (in addi ion o a coo dina ed wa e molecule), and a hyd oxyl
b idge, which ac s as connec o among neighbo ing me allic cen e s. No e ha , aking in o
conside a ion ha me als a e andomly dis ibu ed wi hin he c ys al s uc u e, a en a i e
o mula is p esen ed, which is co obo a ed by bulk p ope ies o he ma e ial (see ICP-AES
esul s in Table S2 o SEM-EDX esul s in Figu e S3).
The e o e, ega ding he me al en i onmen , wo su oundings a e desc ibed: nine
coo dina ed MN
3
O
6
and eigh coo dina ed MO
8
en i onmen s, which, acco ding o con-
inuous shape measu emen s, con i m he sphe ical capped squa e an ip ism (TCTPR-9)
and iangula dodecahed on (TDD-8) polyhed a, espec i ely. The o me coo dina ion
en i onmen is composed o h ee hyd oxyl oxygens and amino a oms om L in addi ion
o h ee addi ional oxygen a oms belonging o ligand hyd oxyl g oup. The la e me allic
nucleus is composed o he coo dina ion o a wa e sol en molecule, an oxygen belonging
o a hyd oxyl b idge, along wi h six oxygen a oms, co esponding o wo ligand hyd oxyl
and wo ca boxyla e moie ies.
As a o emen ioned, hyd oxyl b idges
µ3
-OH
−
join me allic cen e s cons uc ing
M
5
(OH)
3
seconda y building uni s in he s uc u e, being he ligand connec o , among
di e en sbu. Rega ding he connec i i y o he sup amolecula en i y, om he opological
poin o iew, six-connec ed nodes a e desc ibed, which, acco ding o TOPOS so wa e [
31
]
examina ion, he amewo k disposed o he
acs
ne wo k wi h he (4
9·
6
6
) poin symbol.
In insic po osi y, cha ac e ized by h ee dimensional mic opo es o 10.1
×
13.3 Å o
Y/Eu-
MOF
(acco ding o PLATON- 1.18 [
32
] ca i ies, co esponds o 19% o he olume o he
s uc u e) and enables sol en c ys alliza ion molecules o be apped, whi ing he po es;
conc e ely, DMF molecules ha e been demons a ed o be loca ed in he mic ochannels
(Figu e 1).
Ca alys s 2022,12, 299 3 o 10
Ca alys s 2022, 12, x FOR PEER REVIEW 3 o 10
o Y/Eu-MOF (acco ding o PLATON- 1.18 [32] ca i ies, co esponds o 19% o he ol-
ume o he s uc u e) and enables sol en c ys alliza ion molecules o be apped, whi ing
he po es; conc e ely, DMF molecules ha e been demons a ed o be loca ed in he mic o-
channels (Figu e 1).
Figu e 1. Pe spec i e iew o he (a) me al coo dina ion en i onmen s ound in he e obime allic
compound Y/Eu-MOF. (b) View o he pen ame allic nodous, whe e M
5
(OH)
3
sbu a e app eciable.
(c) View o he o ma ion o he 1 D channels; (d) he ca i ies p esen in he s uc u e along he a
axis. Colo code: Y (g een), Eu (pu ple), C (g ey), O ( ed), N (blue), and H (whi e). No e ha , due o
he al e ing and andomly o ien ed disposi ion me als, an app oxima ed ep esen a ion has been
pe o med, aking in o conside a ion p oposed o mula o {[Y
3.5
Eu
1.5
L
6
(OH)
3
(H
2
O)
3
]·12DMF}
n
.
2.2. Chemical Composi ion
Single-c ys al X- ay di ac ion allowed o p oposing an app oxima ed o mula o
he he e obime allic ca alys , which was u he con i med by FT-IR, ICP-AES, PXRD, and
SEM-EDX. Fo a de ailed explana ion o PXRD and FT-IR, please check suppo ing in o -
ma ion, Figu es S1 and S2, espec i ely.
ICP-AES analysis, conduc ed in he he e obime allic compound Y/Eu-MOF, exhib-
i ed an y ium con en o 1672 mg/L (co esponding o 18.8 mM o Y
3+
) and eu opium
con en o 1268 mg/L (8.34 mM Eu
3+
). The calcula ed Y o Eu ela ionship gi es 2.25, which
is e y much in line wi h he p oposed o mula, whe e a p opo ion o 2.33 is expec ed.
Addi ionally, SEM-EDX mapping con i ms ha bo h me als a e p esen in single c ys al.
Howe e , he mapping spec um, pe o med in one single c ys al, showed ela i ely
highe Y
3+
o Eu
3+
p opo ions; o he c ys al in which spec um was collec ed, a ela ion-
ship o 3.25, ega ding o Y o Eu, was calcula ed. This is due o he une en dis ibu ion
o me als h oughou he ca alys s uc u e. None heless, he p oposed o mula, which is
de i ed by single c ys al X- ay di ac ion, powde X- ay di ac ion, SEM–EDX, and ICP-
Figu e 1.
Pe spec i e iew o he (
a
) me al coo dina ion en i onmen s ound in he e obime allic
compound
Y/Eu-MOF
. (
b
) View o he pen ame allic nodous, whe e M
5
(OH)
3
sbu a e app eciable.
(
c
) View o he o ma ion o he 1 D channels; (
d
) he ca i ies p esen in he s uc u e along he a
axis. Colo code: Y (g een), Eu (pu ple), C (g ey), O ( ed), N (blue), and H (whi e). No e ha , due
o he al e ing and andomly o ien ed disposi ion me als, an app oxima ed ep esen a ion has been
pe o med, aking in o conside a ion p oposed o mula o {[Y3.5Eu1.5L6(OH)3(H2O)3]·12DMF}n.
2.2. Chemical Composi ion
Single-c ys al X- ay di ac ion allowed o p oposing an app oxima ed o mula o
he he e obime allic ca alys , which was u he con i med by FT-IR, ICP-AES, PXRD,
and SEM-EDX. Fo a de ailed explana ion o PXRD and FT-IR, please check suppo ing
in o ma ion, Figu es S1 and S2, espec i ely.
ICP-AES analysis, conduc ed in he he e obime allic compound
Y/Eu-MOF
, exhibi ed
an y ium con en o 1672 mg/L (co esponding o 18.8 mM o Y
3+
) and eu opium con en
o 1268 mg/L (8.34 mM Eu
3+
). The calcula ed Y o Eu ela ionship gi es 2.25, which is
e y much in line wi h he p oposed o mula, whe e a p opo ion o 2.33 is expec ed.
Addi ionally, SEM-EDX mapping con i ms ha bo h me als a e p esen in single c ys al.
Howe e , he mapping spec um, pe o med in one single c ys al, showed ela i ely highe
Y
3+
o Eu
3+
p opo ions; o he c ys al in which spec um was collec ed, a ela ionship
o 3.25, ega ding o Y o Eu, was calcula ed. This is due o he une en dis ibu ion
o me als h oughou he ca alys s uc u e. None heless, he p oposed o mula, which
is de i ed by single c ys al X- ay di ac ion, powde X- ay di ac ion, SEM–EDX, and
ICP-AES, is consis en and summa izes he bes app oxima ion o da a ob ained in he
a o emen ioned echniques.
2.3. Chemical S abili y and Elec opho e ic Beha io
ζ
-po en ial is one o he undamen al pa ame e s no mally used o measu e he mag-
ni ude o he elec os a ic (o cha ge) epulsion o a ac ion be ween pa icles, being an
Ca alys s 2022,12, 299 4 o 10
indi ec es ima e o he su ace cha ge densi y o he sys ems and helping o de e mine he
epulsi e in e ac ions be ween colloidal pa icles, as well as he endency o agg ega ion.
Sys ems wi h high
ζ
-po en ial (
−
/
+
) a e conside ed elec ically s able, whe eas colloids wi h
low
ζ
-po en ial (
−
/
+
) a e usually e e ed o as sys ems ha end o agg ega e and u he
p ecipi a e. In his s udy, measu emen s we e always conduc ed a a ixed conduc i i y
o 330
µ
S/cm, which is equi alen o a concen a ion o abou 3.7 mM NaCl (Figu e S7).
The highes nega i e alue o he
ζ
-po en ial, ob ained wi h
Y/Eu-MOF
, was eached a
pH 10 (
−
35.8
±
0.5 mV, elec opho e ic mobili y o
−
2.252
±
0.035
µ
mcm/Vs), sugges ing
ha : (i) he dissocia ion o ex e nal acidic g oups ha e occu ed, con e ing he o e all
nega i e cha ge (Figu es S8 and S9, Table S7); (ii) he MOF pa icles will end o epel each
o he , and he e will be no endency o he pa icles o come oge he a his basic pH,
due o his la ge alue o
ζ
-po en ial. Howe e , when educing he pH o he solu ions,
he
ζ
-po en ials alues s a ed o inc ease, e idencing an isoelec ic poin be ween pH 4
and 5. Simila esul s we e p e iously epo ed by ou g oup. The
Eu-MOF
ca alys , wi h
he highes nega i e alue o
ζ
-po en ial, was also ob ained a pH 10 (
−
25.0
±
0.6 mV);
howe e , in his case, he isoelec ic poin was ob ained be ween pH 8 and 9 (Figu e 2).
F om an elec opho e ic beha io poin o iew, he mixed na u e o MOF con e s bo h a
highe s abili y, as a unc ion o pH, and less endency o agg ega e.
Ca alys s 2022, 12, x FOR PEER REVIEW 4 o 10
AES, is consis en and summa izes he bes app oxima ion o da a ob ained in he a o e-
men ioned echniques.
2.3. Chemical S abili y and Elec opho e ic Beha io
ζ-po en ial is one o he undamen al pa ame e s no mally used o measu e he mag-
ni ude o he elec os a ic (o cha ge) epulsion o a ac ion be ween pa icles, being an
indi ec es ima e o he su ace cha ge densi y o he sys ems and helping o de e mine
he epulsi e in e ac ions be ween colloidal pa icles, as well as he endency o agg ega-
ion. Sys ems wi h high ζ-po en ial (−/+) a e conside ed elec ically s able, whe eas colloids
wi h low ζ-po en ial (−/+) a e usually e e ed o as sys ems ha end o agg ega e and
u he p ecipi a e. In his s udy, measu emen s we e always conduc ed a a ixed con-
duc i i y o 330 µS/cm, which is equi alen o a concen a ion o abou 3.7 mM NaCl (Fig-
u e S7). The highes nega i e alue o he ζ-po en ial, ob ained wi h Y/Eu-MOF, was
eached a pH 10 (−35.8 ± 0.5 mV, elec opho e ic mobili y o −2.252 ± 0.035 µmcm/Vs),
sugges ing ha : (i) he dissocia ion o ex e nal acidic g oups ha e occu ed, con e ing he
o e all nega i e cha ge (Figu es S8 and S9, Table S7); (ii) he MOF pa icles will end o
epel each o he , and he e will be no endency o he pa icles o come oge he a his
basic pH, due o his la ge alue o ζ-po en ial. Howe e , when educing he pH o he
solu ions, he ζ-po en ials alues s a ed o inc ease, e idencing an isoelec ic poin be-
ween pH 4 and 5. Simila esul s we e p e iously epo ed by ou g oup. The Eu-MOF
ca alys , wi h he highes nega i e alue o ζ-po en ial, was also ob ained a pH 10 (−25.0
± 0.6 mV); howe e , in his case, he isoelec ic poin was ob ained be ween pH 8 and 9
(Figu e 2). F om an elec opho e ic beha io poin o iew, he mixed na u e o MOF con-
e s bo h a highe s abili y, as a unc ion o pH, and less endency o agg ega e.
Figu e 2. Compa ison o ζ-po en ial beha io , as a unc ion o pH, ob ained wi h Y/Eu-MOF and
Eu-MOF. All he measu emen s we e pe o med wi h a cons an conduc i i y o 330 µS/cm.
In o de o de e mine he pa icle size dis ibu ion o he ca alys in he suspended
and deposi ed ac ion, op ical mic oscope images we e assayed (Figu es S4 and S5). The
ca alys was suspended in dis illed wa e ; he suspension was shaken igo ously and sub-
sequen ly le o sedimen a ion o 5 min, and he suspended ac ion sepa a ed. The de-
posi ed ac ion was composed o 68% o he o al amoun o ca alys ini ially weigh ed,
ha ing an a e age pa icle size dis ibu ion o 12 ± 6 µm (Figu e S4). The suspended ac-
ion showed an a e age pa icle size o 8 ± 4 µm (Figu e S5). Ob ained alues a e ela i ely
simila o SEM images, in which single c ys als and la ge agg ega es a e app ecia ed.
5.9
-1.0
-5.1 -6.7 -8.5
-18.1
-35.8
2.4 1.1 1.3
6.3 4.0
-6.9
-25.0
-45
-35
-25
-15
-5
5
15
45678910
ζ-Po en ial (mV)
pH
Y/Eu-MOF
Eu-MOF
Figu e 2.
Compa ison o
ζ
-po en ial beha io , as a unc ion o pH, ob ained wi h
Y/Eu-MOF
and
Eu-MOF. All he measu emen s we e pe o med wi h a cons an conduc i i y o 330 µS/cm.
In o de o de e mine he pa icle size dis ibu ion o he ca alys in he suspended
and deposi ed ac ion, op ical mic oscope images we e assayed (Figu es S4 and S5). The
ca alys was suspended in dis illed wa e ; he suspension was shaken igo ously and
subsequen ly le o sedimen a ion o 5 min, and he suspended ac ion sepa a ed.
The deposi ed ac ion was composed o 68% o he o al amoun o ca alys ini ially
weigh ed, ha ing an a e age pa icle size dis ibu ion o 12
±
6
µ
m (Figu e S4). The
suspended ac ion showed an a e age pa icle size o 8
±
4
µ
m (Figu e S5). Ob ained
alues a e ela i ely simila o SEM images, in which single c ys als and la ge agg ega es
a e app ecia ed. Taking in o conside a ion he a e age pa icle size dis ibu ion in he
suspension, i is sugges ed ha single-c ys als emain ela i ely well-suspended, and
agg ega es o supe io size end o deposi .
2.4. S udy o he Ca aly ic Ac i i y
The ca aly ic ac i i y o
Y/Eu-MOF
(0.5 mol%) was ini ially e alua ed in he cyanosi-
lyla ion eac ion o ca bonyl compounds (
Y/Eu-MOF
) using TMSCN as he nucleophile,
sol en ee eac ion condi ions, oom empe a u e, and N
2
a mosphe e. These condi ions
Ca alys s 2022,12, 299 5 o 10
ha e been al eady epo ed in ou p e ious wo ks, wi h monome allic Y o Eu MOF syn-
he ized wi h he same ligand H
2
L (3-amino-4-hyd oxybenzoic acid) [
15
], ob aining only
8% con e sion a e 14 h when he blank eac ion was es ed.
The scope o he eac ion was e alua ed wi h i e highly eac i e aldehydes o di e en
na u es, such as a oma ic, he e oa oma ic, and alipha ic, demons a ing ha independen ly
o he na u e o he subs i uen , he eac ion akes place wi h e y good o excellen
con e sions (89–99%), a e only 24 h (Scheme 1). La e on, less eac i e and s e ically
demanding ke ones we e es ed, obse ing a signi ican dec ease in con e sion (74–77%),
when elec on-dona ing o -wi hd awing subs i uen s we e loca ed a he pa a-posi ion,
whe eas, again, excellen con e sion we e achie ed wi h a oma ic, he e oa oma ic, and
alipha ic subs a es (91–99%) (Scheme 1). These esul s o e pass he ones published, un il
he momen o o he g oups [
21
–
23
], and ha e simila ca aly ic beha iou wi h ou p is ine
Eu-MOF.
Ca alys s 2022, 12, x FOR PEER REVIEW 5 o 10
Taking in o conside a ion he a e age pa icle size dis ibu ion in he suspension, i is
sugges ed ha single-c ys als emain ela i ely well-suspended, and agg ega es o supe-
io size end o deposi .
2.4. S udy o he Ca aly ic Ac i i y
The ca aly ic ac i i y o Y/Eu-MOF (0.5 mol%) was ini ially e alua ed in he cyanosi-
lyla ion eac ion o ca bonyl compounds (Y/Eu-MOF) using TMSCN as he nucleophile,
sol en ee eac ion condi ions, oom empe a u e, and N2 a mosphe e. These condi ions
ha e been al eady epo ed in ou p e ious wo ks, wi h monome allic Y o Eu MOF syn-
he ized wi h he same ligand H2L (3-amino-4-hyd oxybenzoic acid) [15], ob aining only
8% con e sion a e 14 h when he blank eac ion was es ed.
The scope o he eac ion was e alua ed wi h i e highly eac i e aldehydes o di -
e en na u es, such as a oma ic, he e oa oma ic, and alipha ic, demons a ing ha inde-
penden ly o he na u e o he subs i uen , he eac ion akes place wi h e y good o ex-
cellen con e sions (89–99%), a e only 24 h (Scheme 1). La e on, less eac i e and s e i-
cally demanding ke ones we e es ed, obse ing a signi ican dec ease in con e sion (74–
77%), when elec on-dona ing o -wi hd awing subs i uen s we e loca ed a he pa a-po-
si ion, whe eas, again, excellen con e sion we e achie ed wi h a oma ic, he e oa oma ic,
and alipha ic subs a es (91–99%) (Scheme 1). These esul s o e pass he ones published,
un il he momen o o he g oups [21–23], and ha e simila ca aly ic beha iou wi h ou
p is ine Eu-MOF.
Scheme 1. Scope o he cyanosilyla ion eac ion using aldehydes and ke ones.
As a con inua ion o he s udy o he ca aly ic ac i i y o Y/Eu-MOF, we decided o
go one s ep o wa d and es , o he i s ime, he hyd obo a ion eac ion o ca bonyl
compounds wi h a lan hanide based-MOF ca alys . Fo ha , he op imiza ion o he eac-
ion condi ions was ca ied ou (Table S8). Fi s o all, he eac ion was es ed wi h sol en s
o di e en na u es, as well as wi hou sol en (en ies 1–5), ob aining he bes esul in
he absence o sol en (en y 1, Table S8). Finally, he amoun o ca alys was also es ed
(en ies 6–8), obse ing ha , wi h a sligh inc ease om 0.35 o 0.5 mol%, he eac ion ook
place wi h ull con e sion (en y 6).
Wi h he op imal eac ion condi ions in hand, he scope o he eac ion was e alua ed
again, using a b oad ange o di e en ke ones (Scheme 2). The use o elec on-dona ing
Scheme 1. Scope o he cyanosilyla ion eac ion using aldehydes and ke ones.
As a con inua ion o he s udy o he ca aly ic ac i i y o
Y/Eu-MOF
, we decided o
go one s ep o wa d and es , o he i s ime, he hyd obo a ion eac ion o ca bonyl
compounds wi h a lan hanide based-MOF ca alys . Fo ha , he op imiza ion o he eac ion
condi ions was ca ied ou (Table S8). Fi s o all, he eac ion was es ed wi h sol en s
o di e en na u es, as well as wi hou sol en (en ies 1–5), ob aining he bes esul in
he absence o sol en (en y 1, Table S8). Finally, he amoun o ca alys was also es ed
(en ies 6–8), obse ing ha , wi h a sligh inc ease om 0.35 o 0.5 mol%, he eac ion ook
place wi h ull con e sion (en y 6).
Wi h he op imal eac ion condi ions in hand, he scope o he eac ion was e alua ed
again, using a b oad ange o di e en ke ones (Scheme 2). The use o elec on-dona ing
g oups in he pa a-posi ion o he a oma ic ing nega i ely in luenced he ca aly ic eac ion,
causing he eac ion ime o inc ease om 24 o 48 o e en 120 h, in o de o ob ain
mode a e con e sions (45–67%). This in luence on he inc ease in eac ion ime did no
ake place when elec on-wi hd awing subs i uen s we e used, obse ing ha , ega dless
o he posi ion o he a oma ic ing in which he subs i uen s we e ound, yields we e
good (71–90%). Fu he mo e, he e oa oma ic ke ones eached good esul s in only 24 h
o eac ion (88%). The s e ic hind ance o ke ones, such as
1j
and
1p
, needed supe io
eac ion imes o 48 and 120 h, espec i ely, in o de o achie e ull con e sion. Alipha ic
ke ones, wi h di e en na u es, we e es ed and p o ided good esul s (95–99%). Then, we
decided o es cyclic ke ones, which a e usually less employed, ob aining mode a e esul s
Ca alys s 2022,12, 299 6 o 10
(61–63%). Finally, he chemoselec i i y o he eac ion was pu sued by employing ke ones
bea ing double bonds and es e g oups, achie ing, in bo h cases, he speci ic educ ion o
he ca bonyls; al hough, in he la e , he con e sion was lowe han 5%, due o he poo
solubili y o he subs a e in HBpin.
1
Scheme 2.
Scope o he hyd obo a ion eac ion o ke ones. Reac ion ca ied ou o 24 h.
a
Reac ion
ca ied ou du ing 24 h; bReac ion ca ied ou du ing 48 h; cReac ion ca ied ou du ing 120 h.
Ano he impo an issue ha needed o be add essed was i ou ca alysis was he
objec o hidden bo on ca alysis [
33
]. To dis inguish be ween “ ue” ca alysis and BH
3
ca alysis, o eac ions using HBpin, we pe o med wo complemen a y expe imen s. Wi h
he help o
1
H and
11
B NMR, we pu sued he possible MOF-p omo ed BH
3
o ma ion by
moni o ing he mix u e o ou MOF ca alys and HBpin unde ca aly ic condi ions. The
lack o BH
3
signals was e idenced du ing he whole expe imen , p o ing ha ou MOF
ca alys does no p omo e o ma ion o BH
3
. In addi ion, we pe o med he hyd obo a ion
o ace ophenone wi h BH
3·
THF, ins ead o wi h HBpin, showing no subs a e con e sion
and, he e o e, u he e i ying ha , unde ou ca aly ic condi ions, hidden bo on ca alysis
does no exis .
2.5. Recyclabili y and Leaching S udies o he Ca alys
Recyclabili y es s we e also in es iga ed, in o de o s udy he he e ogeneous na-
u e o he ca alys . A e s anda d eac ion condi ions, using ace ophenone as subs a e
(Schemes S1 and S2), he ca alys was isola ed om he eac ion mix u e ia cen i uga ion
and washed se e al imes wi h dichlo ome hane. The ca alys was d ied unde acuum
Ca alys s 2022,12, 299 7 o 10
and hen cha ged wi h a new se o eagen s, in o de o e alua e i s ecyclabili y. The co e-
sponding p oduc s we e ob ained in a 28% and 61% o cyanosilyla ion and hyd obo a ion,
espec i ely, and, in ano he consecu i e cycle, 0% and 15% o con e sion, espec i ely, was
achie ed (Figu e S10). A leaching es was also ca ied ou , in he case o he hyd obo a ion
eac ion (Scheme S3). Fo ha , a e he i s and second eac ion o ecyclabili y es , he
ca alys was emo ed by cen i uga ion and supe na an was il e ed h ough a plug o
celi e and d ied unde acuum. Then, 1-(py idin-2-yl)e han-1-one (
1i
) and HBpin we e
added o he c ude o he co esponding eac ion cycle, and he eac ion was s i ed unde
ine N
2
a mosphe e a oom empe a u e o 24 h. A e ha ime, an aliquo was analysed
by
1
H NMR, ob aining, in he i s cycle, a 38% o con e sion and, in he second cycle, a
13% o p oduc , co obo a ing he leaching o Y o Eu.
2.6. G een Chemis y Me ics
G een chemis y me ics such as a omic economy (AE), mass in ensi y (MI), eac ion
mass e iciency (RME), and ca bon e iciency (CE) we e calcula ed o bo h eac ions
s udied (Table S9), in o de o e alua e i he eac ions a e eco- iendly and can o e come
en i onmen al and heal h p oblems. The ob ained alues o cyanosilyla ion eac ion we e
100% o AE, 1.127 o MI, 95.7% o RME, and 96.8% o CE. These esul s a e compa able
o hose desc ibed p e iously o ela ed lan hanide-based MOFs [
15
,
16
,
19
,
20
]. In he case
o he hyd obo a ion eac ion, hese alues dec eased conside ably, down o 49.1%, 2.406,
46.8%, and 52.1% o AE, MI, RME, and CE, espec i ely, due o he inal hyd olysis and
consequen loss o a oms in he inal p oduc (Table S9).
3. Ma e ials and Me hods
3.1. Ma e ials
All expe imen s in ol ing mois u e-sensi i e compounds we e pe o med unde an
ine a mosphe e o N
2
using s anda d echniques. Unless o he wise indica ed, eagen s
and subs a es we e pu chased om comme cial sou ces and used as ecei ed. Me allic
p ecu so s, such as eu opium (III) ni a e pen ahyd a e (99.9%, Al a Aesa ), and y ium
(III) ni a e hexahyd a e (99.9% o pu i y, Fluo ochem), we e used as ecei ed, as well as 3-
amino-4-hyd oxybenzoic acid ligand (H
2
L, C
7
H
7
NO
3
, 97% o pu i y), which was pu chased
om Fluo ochem. Sol en s no equi ed o be d y we e pu chased as echnical g ade and
used as ecei ed. Con e sion alues ela i e o he limi ing eagen we e calcula ed om he
1
H NMR spec a o he eac ion c udes. Isola ed p oduc s o cyanosilyla ion eac ion we e
ob ained a e cen i uga ion (12,300 pm, 5 min, 20
◦
C) and washed wi h dichlo ome hane
(2
×
0.5 mL), in o de o emo e he ca alys o column ch oma og aphy in silica gel using
hexane as eluen . Fo he hyd obo a ion eac ion, i s o all he hyd olysis o he p oduc
was ca ied ou adding NaOH (0.1 M, 0.5 mL) and E
2
O (0.5 mL) and s i ing he mix u e
o e nigh ; a e ha , he ca alys was emo ed ia cen i uga ion (12,300 pm, 5 min, 20
◦
C)
and washed wi h dichlo ome hane (2 ×0.5 mL).
3.2. Syn hesis o Ca alys and Gene al P ocedu es o Ca alysis
Syn hesis o {[Y3.5Eu1.5L6(OH)3(H2O)3]·12DMF}n, namely Y/Eu-MOF:
The 3-amino-
4-hyd oxybenzoic acid (0.010 g, 0.0625 mmol) was dissol ed in 0.2 mL o DMF con aining
10
µ
L o E
3
N (0.072 mmol). In a sepa a e ial, Eu(NO
3
)
3·
5H
2
O (0.006 g, 0.0145 mmol)
and Y(NO
3
)
3·
6H
2
O (0.011 g, 0.0289 mmol) sal s we e dissol ed in o a 0.8 mL o dis illed
wa e . A e dissolu ion, 0.2 mL o DMF and 0.8 mL o H
2
O we e added o he me al and
ligand solu ions, espec i ely. Finally, he me al solu ion was added d opwise and unde
con inuous agi a ion o he ligand solu ion. The ob ained b own solu ion was in oduced o
he o en a 100 ◦C o 2 h in a sc ew-capped ial (6 mL) o yield hexagonal single c ys als.
Fo he eac ion scaling up syn he ic p ocedu e, consul he suppo ing ma e ial.
Gene al p ocedu e o he cyanosilyla ion eac ion
: In a 1 mL ial, wi h a sep um
sc ew capped, equipped wi h a s i ing ba ,
Y/Eu-MOF
ca alys (0.5 mol%) was weighed.
Subsequen ly, he co esponding amoun o ca bonylic compound
1
(0.25 mmol) was
Ca alys s 2022,12, 299 8 o 10
added, ollowed by ime hylsilyl cyanide (TMSCN) (34
µ
L, 0.275 mmol, 1.1 equi .), and
he eac ion was s i ed unde ine N
2
a mosphe e a oom empe a u e o 24 h. Once he
eac ion was inished, he ca alys was emo ed by cen i uga ion (12,300 pm, 5 min) and
washed wi h DCM (2
×
0.5 mL), ob aining he co esponding pu e p oduc s
2
and
3
, a e
emo al o he sol en wi h o a y e apo a o . When no ull con e sion was eached, he
p oduc was pu i ied by column ch oma og aphy using hexane as eluen .
Gene al p ocedu e o he hyd obo a ion eac ion
: In a 1 mL ial, wi h a sep um
sc ew capped, equipped wi h a s i ing ba ,
Y/Eu-MOF
ca alys (0.5 mol%) was weighed.
Subsequen ly, he co esponding amoun o ca bonylic compound
1
(0.25 mmol) was added,
ollowed by pinacolbo ane (HBpin) (40
µ
L, 0.275 mmol, 1.1 equi .), and he eac ion was
s i ed unde ine N
2
a mosphe e a oom empe a u e o he co esponding ime, as
indica ed on he able. A e ha ime, he hyd olysis o he inal p oduc was ca ied ou
adding NaOH (0.1 M, 0.5 mL) and E
2
O (0.5 mL), and he mix u e was s i ed o e nigh .
Once he eac ion was inished, he ca alys was emo ed by cen i uga ion (12,300 pm,
5 min) and washed wi h DCM (2
×
0.5 mL), ob aining he co esponding p oduc
4
a e
emo al o he sol en wi h o a y e apo a o . When no ull con e sion was eached he
p oduc was pu i ied by column ch oma og aphy.
4. Conclusions
All in all, o he bes o ou knowledge, we epo he i s mixed he e obime allic
Y/Eu-MOF
, based on a 3-amino-4-hyd oxylbenzoic acid ligand, wi h imp essi e ca aly ic
e iciency in he cyanosilyla ion and hyd obo a ion eac ion o ca bonyl compounds, bu
educed ecyclabili y, compa ed o he ela ed MOFs. The ca alys has been ho oughly cha -
ac e ized by means o X- ay c ys allog aphy, FTIR, ICP-AES, and PXRD; i s elec opho e ic
beha io , as a unc ion o pH, has been also assayed, showing a nega i e su ace cha ge
wi h a e y low endency o agg ega e.
Supplemen a y Ma e ials:
The ollowing suppo ing in o ma ion can be downloaded a : h ps:
//www.mdpi.com/a icle/10.3390/ca al12030299/s1. Table S1: Elemen al analysis o compounds
Y/Eu-MOF. Table S2: ICP-AES esul s o compound Y/Eu-MOF. Table S3: C ys allog aphic da a
and s uc u e e inemen de ails o compound Y/Eu-MOF. Table S4: Selec ed bond leng hs (Å) and
angles (
◦
) o compound Y/Eu-MOF. Table S5: Table o he con inuous Shape Measu emen s o
he MN
3
O
6
coo dina ion en i onmen . Table S6: Table o he con inuous Shape Measu emen s o
he MO8coo dina ion en i onmen . Table S7: Elec opho e ic mobili y and ζ-po en ial dependence,
wi h he pH o he Y/Eu-MOFs pa icles dispe sed in wa e . Conduc i i y ixed a 330
µ
S/cm.
Table S8: Op imiza ion o he eac ion condi ions in he hyd obo a ion eac ion. Table S9: G een
me ics calcula ed o Y/Eu-MOF ca alys . Table S10: Ca aly ic cyanosilyla ion o benzaldehyde
pe o mances o Ln-MOFs, as epo ed in he li e a u e. Figu e S1: Figu e o he pa e n ma ching
analysis and expe imen al PXRD o Y/Eu-MOF. Figu e S2: Figu e o he in a ed spec a o he
ligand and Y/Eu-MOF. Figu e S3: SEM and EDS mapping o bulk ma e ial o Y/Eu-MOF. Figu e
S4: Images and pa icle size dis ibu ion (an o e all o 250 pa icles) in he deposi ed ac ion o
Y/Eu-MOF ca alys non-suspended in wa e (abou a 68% o he o al amoun ), de e mined om
op ical mic oscope images. Figu e S5: Images and pa icle size dis ibu ion (an o e all o 250 pa icles)
o Y/Eu-MOF c ys als in he ac ion s eadily suspended in wa e (abou a 32% o he o al amoun ),
de e mined om op ical mic oscope images. Figu e S6: Compa a ion o he pa icle size dis ibu ion
o Y/Eu-MOF in he ac ion s eadily suspended in wa e and he non-suspended, de e mined om
op ical mic oscope images. Figu e S7: Calib a ion line o conduc i i y (
µ
S/cm) s [NaCl] (mol/L).
Figu e S8:
ζ
-po en ial (mV) dependence wi h he pH o he Y/Eu-MOF. All he measu emen s we e
pe o med wi h cons an conduc i i y o 330
µ
S/cm. Figu e S9: Elec opho e ic mobili y (
µ
m
·
cm/V
·
s)
dependence wi h he pH o he Y/Eu-MOF. All he measu emen s we e pe o med wi h cons an
conduc i i y o 330
µ
S/cm. Figu e S10: S udy o he ecyclabili y o Y/Eu-MOF (0.5 mol%) ca alys
on he cyanosilyla ion and hyd obo a ion eac ion o ace ophenone as ca bonyl subs a e. Figu e S11:
Analysis o he TOF (h
−1
) ob ained in he cyanosilyla ion eac ion o ace ophenone a di e en imes
o eac ion wi h Y/Eu-MOF (0.5 mol%), wi h he op imized eac ion condi ions. Figu e S12: Analysis
o he TOF (h
−1
) ob ained in he hyd obo a ion eac ion ace ophenone a di e en imes o eac ion
wi h Y/Eu-MOF (0.5 mol%), wi h he op imized eac ion condi ions. Scheme S1: Reac ion condi ions
Ca alys s 2022,12, 299 9 o 10
used o he s udy o ecyclabili y o Y/Eu-MOF ca alys s in he cyanosilyla ion eac ion. Scheme S2:
Reac ion condi ions used o he s udy o ecyclabili y o Y/Eu-MOF ca alys s in he hyd obo a ion
eac ion. Scheme S3: Leaching es , ca ied ou a e he i s and second cycles.
Au ho Con ibu ions:
Concep ualiza ion, I.F. and A.R.-D.; me hodology, M.E.L.-V., J.M.P. and
E.E.-E
.; so wa e, S.R., D.C.-L. and J.M.S.; alida ion, J.M.P., S.R. and J.M.S.; o mal analysis, A.R.-D.;
in es iga ion, M.E.L.-V., J.M.P. and E.E.-E.; esou ces, I.F., J.M.S. and A.R.-D.; da a cu a ion, S.R. and
D.C.-L.; w i ing-o iginal d a p epa a ion, J.M.P. and E.E.-E.; w i ing- e iew and edi ing, J.M.P. and
S.R.; isualiza ion, I.F.; supe ision, A.R.-D.; p ojec adminis a ion, I.F.; unding acquisi ion, A.R.-D.,
I.F. and J.M.S. All au ho s ha e ead and ag eed o he published e sion o he manusc ip .
Funding:
This esea ch has been unded by he S a e Resea ch Agency (g an s CTQ2017-84334-R
and PGC2018-102052-B-C21) o he Spanish Minis y o Science, Inno a ion and Uni e si ies, he
Eu opean Union (Eu opean Regional De elopmen Fund—ERDF), Jun a de Andalucía (P20_01041,
UAL2020-AGR-B1781, B-FQM-734-UGR20 and FQM-394). E.E., S.R., and J.P. acknowledge he
Go e nmen o he Basque Coun y, Juan de la Cie a Inco po ación (g an no. IJC2019-038894-I) and
Uni e si y o Alme ia (g an no. HIPATIA2021_04) o hei espec i e ellowships.
Da a A ailabili y S a emen : Mo e da a can be ob ained by eques om au ho s.
Con lic s o In e es : The au ho s decla e no con lic o in e es .
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