Can a Paladin use a Necklace of Prayer Beads as slots that can be expended to use the Divine Smite feature?

Question

My level 7 Paladin(2)/Fighter(5) found a necklace of prayer beads. Can those spells bound to the beads be used for Divine Smite?

The relevant part of the paladin's Divine Smite feature description says (emphasis mine):

Starting at 2nd level, when you hit a creature with a melee weapon attack, you can expend one spell slot to deal radiant damage to the target, in addition to the weapon's damage. The extra damage is 2d8 for a 1st-level spell slot, plus 1d8 for each spell level higher than 1st, to a maximum of 5d8. [...]

The relevant part of the description of the necklace of prayer beads says (emphasis mine):

This necklace has 1d4 + 2 magic beads made from aquamarine, black pearl, or topaz. [...] Each bead contains a spell that you can cast from it as a bonus action (using your spell save DC if a save is necessary). Once a magic bead's spell is cast, that bead can't be used again until the next dawn.

Divine Smite explicitly talks of spell slots, while the necklace of prayer beads does not, although the functionality of the beads is quite similar. So from my understanding, using beads in place of spell slots is not intended.

Can a Paladin expend beads from the necklace of prayer beads to use the Divine Smite feature?

Answer 1

The Necklace of Prayer Beads does not provide spell slots. Divine Smite requires spell slots.

The Necklace of Prayer Beads description does not mention spell slots anywhere, so it simply does not provide spell slots. Since Divine Smite requires a spell slot, Divine Smite and the Necklace of Prayer Beads do not interact in any way.

To think about it another way, the Necklace tells you everything it can be used for. If it gave you extra spell slots that you could use with features that require spell slots, it would tell you that. Instead, it tells you that it lets you cast a certain set of predetermined (by the DM) spells once per day using your bonus action. This is what you can do with it.

Answer 2

Spells are not spell slots

Spells and spell slots are two different things. The section of the rules on spell slots explains the difference:

When a character casts a spell, he or she expends a slot of that spell's level or higher, effectively "filling" a slot with the spell. You can think of a spell slot as a groove of a certain size–small for a 1st-level slot, larger for a spell of higher level.

Essentially, a spell slot is the "raw material" that a character expends to cast a spell. And this conversion is one-way–you generally can't convert spells back to spell slots. However, the rules also mention that spell slots are not the only way to cast spells:

Some characters and monsters have special abilities that let them cast spells without using spell slots.

The Necklace of Prayer Beads falls into this category, as do most magic items that allow the user to cast spells. As you've quoted in your question, each bead contains a spell, not a spell slot. Hence, it does not interact with any ability that relies on the use of spell slots, like Divine Smite.