Turn vector made from input$tableID_rows_selected into a dataframe

From what I understand, when I create a DT and do the following, I create a vector of rows that are selected from the DT:

output$plateWells_selected <- renderPrint({
    input$plate_rows_selected
  })

However, since I am trying to use the indices of the selected cells elsewhere in my app, I'm thinking it would be easier to store those indices in a data.frame instead of just printing the indices of the selected rows.

Is there a way to turn the selected row input into a data.frame? Below is my latest attempt after my research, but I get this error:

Error in as.data.frame.default(reactive(input$plate_rows_selected)) : 
  cannot coerce class ‘c("reactiveExpr", "reactive", "function")’ to a data.frame

Here is my MRE:

library(shiny)
library(glue)
library(dplyr)
library(DT)
library(shinyWidgets)
library(tibble)

####Create the matrix and organization for the 96 well plate####
plate96 <- function(id) {
  div(
    style = "position: relative; height: 500px",
    tags$style(HTML('
          
        .wells {
            transform: translateX(50%);
        }

        .wells tbody tr td:not(:first-of-type) {
            border: 1px solid black;
            height: 15px;
            width: 15px;
            padding: 15px;
            font-size: 0;
        }

    ')),
    div(
      style = "position: absolute; left: 50%; transform: translateX(-100%);",
      div(
        class = "wells",
        DTOutput(id, width = "90%", height= "100%")
      )
    )
  )
}


renderPlate96 = function(id, colors = rep("white", 96)) {
  stopifnot(is.character(colors) && length(colors) == 96)
  
  plate <- matrix(1:96, 
                  nrow = 8, 
                  ncol = 12, 
                  byrow = TRUE, 
                  dimnames = list(LETTERS[1:8], 1:12))
  
  colnames (plate) = stringr::str_pad(colnames(plate), 2, "left", "0")
  
  return(plate_return1 <-
           datatable(
             plate,
             options = list(dom = 't', ordering = F),
             selection = list(target = "row"),
             class = 'cell-border compact'
           ) %>%
           formatStyle(
             1:12,
             cursor = 'pointer',
             backgroundColor = styleEqual(1:96, colors, default = NULL)
           )
  )
  
}

ui <- fluidPage(
  br(),
  
  plate96("plate"),
  tags$b("Wells Selected:"),
  verbatimTextOutput("plateWells_selected"),

)

server <- function(input, output, session){
  
  ####Create the 96 well plate image####
  output$plate <- renderDT({
    renderPlate96()
  })
  
  output$plateWells_selected <- renderPrint({
    input$plate_rows_selected
  })
  
  ####Create a DT that stores the values of the cells selected in the plate####
  selected_df <- as.data.frame(reactive(input$plate_rows_selected))

  
}
shinyApp(ui = ui, server = server)